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6,445 |
the steering wheel sometimes shakes at high speeds around 70 miles per hour. It does not always happen. Some day when I am driving at 70, I feel no shakes. some day it shakes badly at the same speed. Also, if I drive slower or faster a speed range (usually between 68 and 75), it never shakes. I did the following, but still the wheel shakes sometimes: I had the left wheel bearing replaced a month ago. The mechanic told me it needs to be replaced. Tires are fine (not perfect, but not bad either). I had them rotated a month ago. I had the front rotars and pads replaced a month ago. When I brake, it does NOT shake. This shaking wheel problem has been around for quite some time (almost two years). What service does the car need? Update: I had the tires balanced, and it is a little bit better now. It is not perfect yet. I was told that the tires are kinda cheap, low quality tires that are not perfectly round.
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Issues involving steering wheel vibrations problems usually are most noticeable at one or two narrow speed ranges (5-10mph and 60-70mph), and will decrease significantly, and in some cases, even disappear outside of these ranges. The amount of vibration caused by worn tires will often be seen over a broader speed range if the tire is worn more. The severity of the vibration is directly related to the vehicles speed. Also, the speed range at which the vibration is felt is also directly related to the amount of wear the tires have endured. At low speeds sometimes a "wobbles" can be felt. These are mostly caused by bent wheels, tires with shifted belts (also referred to as "runout"), and suspension/alignment issues. Tire or Wheel Quality A quick indication of either a poor quality wheel or tire is usually seen by the use of a lot of weights used when balancing the wheel/tire combination. When using a higher end tire on a "straight" wheel you should need somewhere around .5oz of weight per wheel. Tires of inferior quality are often seen with weaker tread layers and belt seating. and may simply just be out of round. Damage Broken Belt When a belt is broken inside of a tire it will cause the tire to "bounce" since it is unable to keep it's form. Think of a tire without a broken belt as a baseball, and the tire with a broken belt as a stress ball. Below is an image of a tire with a broken belt. You can see the bottom of the tread is 100% worn while the top of the tire still has tread left. This was caused by the "bouncing" condition. Slipped Belt With a slipped belt in a tire it will cause the tire to "wobble" and the steering wheel to shake. Here is a image of a severely slipped belt. Wheel Balance (out of round, bent, excessive wear, uneven tread, etc) Usually, neither tires nor wheels are perfect. This is the reason why wheels are balanced whenever tires are replaced and then, rebalanced periodically as they wear. Driving with unbalanced wheels long enough can and will cause flat spots in the tire, which will then always vibrate. Performing a static balance is just not good enough. Balance should always be checked at driving speeds this is known as dynamic balancing. The wheels are removed from the vehicle and one by one put on a Balancing Machine where the mechanic will enter in the appropriate measurements and then the machine will spin the wheel and printout location and amount of weight needed in order to properly balance the wheel. Also, if the wrong type of weights for your wheel type are used, they are likely to come off, giving you an instant balance problem.
Read more: http://mbworld.org/forums/wheels-tires-suspension-brakes-forum-sponsored-tire-rack/111691-causes-wheel-vibration.html#ixzz2agpFwcz5 Suspension & Alignment Suspension Excessively worn suspension components will cause effect the way in which the tire contacts the road. This is due to the fact that if any component (ball-joint, tie-rod, wheel bearing, etc) has excessive play it makes the position because it may make maintaining proper alignment impossible. It may also cause other problems not related to wheel balance and wear. Alignment Maladjusted Camber will not directly cause a vibration, but it can cause uneven and/or rapid tire wear. In turn effect the balance/smoothness of a tires rotation. A lot of mechanics will insist that an improper toe adjustment will not be the cause of a steering wheel vibration, but I remain skeptical. Even if I'm wrong it will still certainly causes rapid and uneven tire wear. Caster has no effect on tire wear but it will effect steering wheel's ability to return after making a turn. Bad alignment is the cause of many tread wear problems that will create vibration issues even if the wheels are perfectly balanced.
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6,788 |
I drive a 2013 Ford Fusion SE with manual transmission. I learned to drive a manual as a kid but picked up a lot of bad habits. In particular I tend to naturally ride the clutch. Now, of course in 1st or Reverse you have to let the clutch slip a little, but I'm having difficulty not letting any slipping from 1st to 2nd. When shifting from 1st to 2nd, will I wear out my clutch or transmission by giving the car some gas as you release the clutch? My feeling is that the answer should be no, I just need to practice and do: "clutch. switch gear. release clutch. gas." but at the appropriate engine speed. I'm confused because many people on various fora say that it's ok to give gas while you're releasing the clutch, but I'm skeptical because this seems like it would wear on the clutch. I obviously do not want to wear out my car.
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Is it ok to give gas while releasing the clutch? Yes, but your goal is to give exactly the right amount of gas. The thing to remember is that the clutch is a consumable part (it's really a whole system of parts that can be consumed but let's pretend that it's a single unique piece for the sake of discussion). As such, it has a finite supply of work that it can do over its service life, useful or otherwise. To clarify, this is what it means to slip the clutch : Between these extremes of engagement and disengagement the clutch
slips to varying degrees. When slipping it still transmits torque
despite the difference in speeds between the engine crankshaft and the
transmission input. Because this torque is transmitted by means of
friction rather than direct mechanical contact, considerable power is
wasted as heat (which is dissipated by the clutch). Properly applied,
slip allows the vehicle to be started from a standstill, and when it
is already moving, allows the engine rotation to gradually adjust to a
newly selected gear ratio. As noted, the clutch is a friction-based part (rather than a direct gear). The above quote means that your goal as the driver is to attempt to ensure that the clutch is spending more time in a static friction mode (i.e., where the frictional surfaces of the clutch are turning at the same speed, pressed tightly together) rather than a kinetic friction mode (i.e., where the frictional surfaces are turning at different speeds and are slipping past each other). This means that the answer to your original question is that it is ok to give exactly the right amount of gas when releasing the clutch pedal. Any more or less than the optimal amount will lead to some slippage of the clutch. Some slippage is to be expected, with wear increasing super-linearly as the difference between target and actual revs increases. The better you are at rev matching, the longer your clutch will last (and the more comfortable your passengers will be). tl;dr: You have to slip the clutch from a stop. In higher gears, your goal is to avoid slipping the clutch. You do this by matching engine speed to transmission speed before releasing the clutch pedal.
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|
7,041 |
Many years ago, I was involved in a hobby of building and flying model aircraft. The aircraft used alcohol-fueled 2-stroke engines with glow plug ignitions. When these engines ran rich (and always at idle), they produced a distinctively different sound to when they ran with the throttle mostly or fully opened and the mixture leaned to deliver the highest RPM. That difference in sound was informally described as "four-stroking". I've heard a similar effect in larger two-stroke engines as well - weed trimmers and motorcyles - so it seems to be a characteristic of two-stroke engines in general, not just the small, model aircraft variety. My question is: what is going on in these engines when they "four-stroke"? It seems as though combustion is only occurring on every other top-dead/power stroke. Is this true? If so, why? What prevents the charge from igniting on one stroke while allowing it to occur on the next, and repeat the alternating pattern? In the case of the glow plug engine, how is it that the glow plug can fail to ignite a charge on one cycle, and still remain hot enough to fire on the next cycle?
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Wikipedia describes four-stroking as: Four-stroking is an undesirable operating condition of two-stroke
engines, where they instead begin to fire every four strokes, rather
than every two strokes. This firing is uneven, noisy and may even
damage the engine if allowed to continue unabated. Four-stroking was
often a cause of poor idling in two stroke engines. It then describes what's happening: Two stroke engines rely on effective scavenging in order to operate
correctly. This clears out the combustion exhaust gases from the
previous cycle and allows refilling with a clean mix of air and fuel.
If scavenging falters, the mixture of unburnable exhaust gas with the
new mixture may produce an overall charge that fails to ignite
correctly. Only when this charge is further diluted, by pumping
through a second volume of clean mixture, does it become inflammable
again. The engine thus begins to 'fire-and-miss' every second cycle
(every four strokes), rather than correctly on every cycle. So, yes it's true that it is only igniting every other intended power stroke. In some worse cases an engine can six- or eight-stroke, igniting every third or fourth power stroke. The reason seems to be that the exhaust isn't purged completely and leans out the mixture on the next stroke and isn't rich enough to ignite leaves a mixture on the next stroke that cannot be ignited until the following stroke which then produces exhaust that again isn't purged completely. The more exhaust left in the cylinder, the more skipped strokes. Model engines are affected differently because of their small scale: Four-stroking is a common and expected behaviour with model engines,
both glow fuel and diesel. These small engines run at extremely high
rotational speeds and their scavenging relies upon this. When started,
they run as inertially-scavenged four strokes and have a distinctive
change in engine note when they accelerate past the point at which
they begin to operate as two strokes. Owing to the scaling laws of
such small engines, this four-stroking is an unavoidable consequence
of limitations on their scavenging at slow speeds. However the same
scaling laws also make the effects of four-stroking less severe and so
the engines can idle happily in this mode, without damage. I suppose that the glow-plug in these engines remains hot enough to ignite the fuel but, every other stroke is just too lean to ignite not an ignitable mixture. If it started six- or eight-stroking maybe it would cool too the point where it could no longer ignite the fuel on the strokes with an appropriately combustible mixture.
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|
7,922 |
Car companies advertise the power of an engine at different rpms. Car 1: 80 PS at 6000 rpm Car 2: 85 PS at 6500 rpm What does the power at different rpm mean?
Does it mean Car 1 has better power than Car 2 because it's at lower rpm? Or does the rpm not affect the power comparison?
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What does the power at different rpm mean? Does it mean Car 1 has
better power than Car 2 because it is at lower rpm? It depends. Or does the rpm not affect the power comparison? tl;dr: The rpm of the power peak affects the engine's usability for different applications. The "peak power" number is just one point on the power band of the engine. Ideally, you'd like to know the entire curve (and how its affected by ambient air temperature, altitude, humidity, phases of the moon, etc): In this figure, we see the horsepower and torque curves for two engines (where torque is solid and horsepower is dotted). Remember, torque is the engine working on the axles and, thereby, the wheels and tires. This is what accelerates the car forward. If you know the torque of the engine at a particular rpm, you can calculate the horsepower at that rpm: horsepower = (torque * rpm) / 5252 Admittedly, the above equation is specific to crazy old-time Imperial units. Insert appropriate conversion factors if you'd like to get metric units out instead. Very casually, you can imagine horsepower (or "power" if you're being unit agnostic) as being "that which maintains speed in spite of drag." We generally expect a high horsepower vehicle to have a higher top speed (provided that it has the gearing to reach that speed). Looking at the above equation, you can also see that, in these units, the horsepower and torque curves always cross at 5252 rpms (i.e., the scalar values are equal even though they're totally different units). So what? All of the above helps you understand what the manufacturer is telling you a bit better. What's missing is "what do you want from a car?" Going back to the chart, you can see that the blue line has a torque peak at about 2500 rpm and that it doesn't drop off until about 4000 rpm. This means that, from a stop, the car will feel like it pulls away strongly, right away. However, as the rpms get much higher, the engine will seem to run out of breath, accelerating much slower at 6000 rpm than it was at 1000 rpm. Qualitatively, this is what we would expect from a large-ish displacement normally aspirated engine. The red line has a torque peak at about 5500. It will feel sluggish from a stop and seem to wake up as the rpms increased. From 5500 to 7500, the red engine will out-accelerate the solid engine by a significant margin. This is roughly what we would expect from a smaller engine (and forced injection would only increase this late-rpm peak). The question for the customer is: which do you like better? Qualitative summary: The early torque peak of the solid line is fun from a standing start but you will need to shift early (trading mechanical advantage to get back to the torque peak). Hopefully, you have enough gears to get you to top speed. This profile is often preferred in a street car. The later peaks of the dotted line is sluggish from a standing start but becomes progressively more exciting as revs increase. You won't need to shift as early to stay at peak power, keeping the mechanical advantage for more revs. This profile is often preferred in a race car. Full disclosure: I've owned low-end, high-end and (high-end + turbo) vehicles and I prefer the last combination. I haven't been interested in standing starts from a red light for many years.
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|
8,134 |
I want to know the SOHC and DOHC configurations. On what factors an engine manufacturer decides to go with SOHC or with DOHC, what should I choose? DOHC or SOHC?
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For those who don't know, SOHC and DOHC refer to the following: SOHC - Single Over Head Cam DOHC - Double Over Head Cam A cam refers to a "cam shaft" or the thing which goes bump in the night. The cam has a "bump" or "hump" in it which actuates the valves which allows air into and exhaust out of the cylinder of the engine at the correct time so the engine will run correctly. As for the configurations themselves, in SOHC configurations, the camshaft is placed on top of the head. Here is an example: The wheel at the right of the picture is what the cam belt rides on. This wheel is attached to the cam itself. The cam, then actuates the rocker arms which you can see are pointing to either side of the head. This is an example of a 3-valve per cylinder head (2-intake and 1-exhaust per cylinder). The 2-valve per cylinder is a much mor prevalent configuration. Here is an example of a DOHC: In this example, you can see there are two separate cam shafts riding atop the head. For DOHC heads, the cams can be tied together with a short chain, then have a separate chain/belt which drives the cams, or can have just a single chain/belt which runs the whole thing. DOHC engines usually have a configuration of 2-intake and 2-exhaust valves per cylinder, but in some cases like the configuration Volkswagen-Audi Group (VAG) uses a five valve per cylinder (3-intake and 2 exhaust). In most cases, the cam directly actuates the valve without the use of a rocker arm (it may or may not have a "lifter" between the cam and the valve). The whole purpose of having OHC configurations is to do away with another form of valve actuation, that of pushrods found in the Over Head Valve (OHV), which is found in most American V8 configurations (Ford uses an OHC version for their motors). OHV configurations use a centrally located cam shaft (central to the engine block), and actuates the valves through the use of lifters, pushrods, and rocker arms. The OHC configuration does away with most of this for the reduction of mass in the valve train. This reduction of mass usually means the engine can run safer and cleaner at higher engine speeds due to less inertial pressures on the valve train. Also, since this is more of a direct actuation of the valves, there is less flex (due to push rods) and a more accurate valve actuation occurs. The trade off in this is that the belts/chains/guides which controls all of this usually wear out over a period of time well before the engine's end of life (EOL), where as on an OHV engine, the valve train and timing chain usually will last until the engine is worn out. The OHC configuration is a lot more complex than the OHV in that there are a more parts which can go bad, which can cause catastrophic consequences if it fails. OHC engines are usually "interference motors", which means the valves and the pistons occupy the same space at different times. If the cam belt/chain fails, the valves stop moving, but the pistons do not (right away). The piston will move up into the valves and usually destroy the valves and the entire head assembly. It is imperative that the cam belt/chain maintenance get done on time. There are no warning signs (without taking the engine apart) to tell you when it is worn out, so following the manufacturers replacement interval is very important. As discussed, the DOHC engines usually have more valves per cylinder than the SOHC versions. They will also usually have less parts involved (most DOHC directly actuate the valves, where SOHC usually have rocker arms). More valves means the engine can intake and exhaust more gasses from the engine. Think of a large circle, say one which is 4" across (or say 10cm for you unruly metric folks out there). How many 2" (5cm) circles can you fit within it? The answer is two. Now take the same 4" circle and fit 1.5" circles within it. The number is somewhere around four. A 4" circle has the area of 12.57in/sq. A 2" circle has the area of 3.14 in/sq, and therefor two of those would equate to 6.28 in/sq. With the 1.5" circle, your total would be 7.07 in/sq. (Note: While I'm not sure if four could fit in the circle exactly, the example is valid for educational purposes.) Now imagine these circles are the valves in the cylinder head. The more valves you can fit into the head, the greater the surface area you can cover. The greater surface area allows greater air/exhaust flow into and out of the cylinder. This gives the engine a chance at better volumetric efficiency or VE (basically how well the cylinder fills with the air/fuel mixture). This allows for greater performance from the engine. Manufactures might choose SOHC over DOHC engines due to cost in design and manufacture. They might choose DOHC over SOHC for the performance aspect. I'm sure there are other reasons. What should you do? This site isn't really for giving you my opinion about what you should choose. Basically I would tell you to find vehicles which are within your cost and performance goals. Select several versions of each, test drive them, then make up your own mind. Both OHC versions have a maintenance schedule which should be met with impunity. Other than that, have fun!
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|
8,550 |
Yesterday I was driving home from work and heard a loud noise which I can only really describe as a "clang". After looking at it today, it looks like the spring for the front left (passenger side) suspension has snapped at the bottom. Here is a picture of the damage: I've already had a couple of friends advise that this is still safe to drive in this condition and was really just looking for some clarification that this is, in fact, safe to drive for a very short term basis (since I need it to get to work). I have it booked in to get repaired in a few days so it really will be quite short term, and the mileage covered during this time will be about 60 miles. Keeping in mind that the break is on the first coil, and that the car hasn't lowered all that much in this corner, is this going to be safe for me to drive for a couple of days until it gets repaired?
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I would say this would be fine to drive slowly and carefully over short distances (I've had worse) - but things to be careful of: potholes speed bumps (seriously - watch out) cornering hard high speeds Also try and avoid braking or accelerating hard - gently come to a stop at lights etc as you want to avoid too much nose travel up and down. Get it to the garage asap, though - it is a really easy fix.
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9,037 |
I am old enough to have had about four transmission failures spaced over about 40 years and at no time did any mechanic ever offer to “fix” it; the only diagnosis has been a complete rebuild. This is not what happens to any other part of the car. There are many potential repairs to the engine. Various individual parts can be replaced and/or repaired and even the engine itself can be tinkered with to an amazing extent without ever costing anywhere close to $2500. I’ve even heard of having engines rebuilt for less than that. Not transmissions though; only a rebuild. I’ve asked every mechanic I’ve ever used why and I’ve gotten many different answers – they usually involve something about the transmission being so hard to get to that by the time you’ve hoisted the engine out of the way or done whatever else, you’ve spent enough labor to make it feasible to just rebuild the whole thing. But this doesn’t really ring true for some reason. I can’t see why a manufacturer can’t design some access into the thing that might allow some service. That last mechanic told me that the case and all the gears inside are all original – they only replaced the parts (clutches) that were worn. Surely some sort of access hole could be a part of the design much like the oil pan underneath the engine. My current vehicle's transmission has no drain plug at all that I can see.
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This is one of those things which are easier said than done. To start with, let me show you a picture of a four speed transmission which has been blown apart: All of those hundreds of parts go through the front end of the transmission. If a single part is bad (which it usually is not the case), you have to pull all of this apart in order to diagnose and repair. Like the mechanic you talked to said, it doesn't make sense to replace just the part which is bad while you have it all apart. The parts are pretty much the cheap part of the rebuild (or fix). Why not just make it a brand new transmission through the rebuild process. You could replace the single part, at a cost difference of a couple hundred dollars, only to have it go bad again in the not too distant future when another part goes bad which wasn't replaced. In most cases when a transmission needs repaired, it is one or more of the soft parts which have gone bad. These include the band(s) and clutches. Usually the hard parts, like the gears, do not go bad and are reused after a thorough cleaning and inspection. You also have to consider, the transmission is very susceptible to debris. When these soft part start letting go, it can put a lot of debris through the transmission which the filter cannot keep up with. When the debris starts going around, it will damage other soft parts in the process. Soft parts also tend to wear at about the same pace (within the same group). So, not just one clutch in the clutch pack will go bad, but the entire group of them will go bad. You aren't going to replace just one clutch, you have to replace all of them. One last thing to consider here is that they sell the transmission parts as a kit (with a few exceptions). You aren't just going to buy single parts. By parts in this instance I'm talking about the soft parts ... you can usually buy hard parts separately. There is no other way, with current transmission design, for you to get at any of the parts inside the transmission ... at least the parts which make the vehicle go. The design as it is, is very compact and does the job very well. If there was any way for a mechanic to be able to get to the parts inside without going the way it does now, it wouldn't have the strength to stay together. Believe me when I say, you could be a rich man to design an automatic transmission to do as you are suggesting and still have it as compact and efficient as what is currently offered. The reason you don't see a drain plug on most automatic transmission is because when you change the fluid, you also change the filter. The exception to this is when you take it to a shop and get the transmission flushed. When they do this, they force fluid backwards through your transmission using the cooling lines. This (supposedly) cleans the filter in the process as well as completely exchanges the old fluid for new fluid (to include the torque converter - which doesn't happen when you just drop the pan). The reason for the cost, as you suggested, is because of one, the labor involved in removing the transmission from the car, and two, because not every mechanic can rebuild a transmission. To do it right takes some extra learning. You just cannot throw it together and expect it to work ... and every make/model is different. All of that costs money. Most engines, on the other hand, are pretty much the same (with a few exceptions). They are all pretty much hard parts which go together relatively easy. There are some idiosyncrasies, but for the most part, they're not a big deal. I hope this gives you a flavor for why you aren't going to see too many shops offering to repair your transmission. Again, as the mechanic said, the major part of any transmission repair is the labor for Removal & Replacement of the transmission itself.
|
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|
9,047 |
My riding experience: 1 day. Already I'm an idiot. This will probably be a good laugh for most of you. I purchased a used bike, Yamaha VStar 250, <2,000 miles, <4 years old. Battery has not been replaced, but owner kept his bike garaged with the battery on a tender. I don't know how old the gas is, but it's safe to assume it's probably less than 6 months old. I was taking a cruise to remind myself how to ride. Halfway through, stalling out on a turn, I had a mental blip. I switched shifting up with shifting down. After a few times trying to start it in 5th instead of first with the choke fully engaged, clutch in, (thinking I was stalling out), the engine doesn't turn. It wasn't until afterward that I found neutral and realized I was in the wrong gear all that time. At first, I could hear a turning noise and the turning would stop and I'd hear a faint buzzing noise. Now I only get the buzzing noise. During the turns, you could see power to the headlamp diminish. I can hear gas sloshing around and I tried starting on the reserve, but that did nothing (can you even start a bike on reserve??). The owner warned me that I ought to fire it up soon and burn through the bas, as the tank had sat around for a relatively long period. However, it has started fine initially, when it actually was in first, and before my mental lapse as to where the gears actually are. I suspect I may have flooded the carb by attempting to have actually accelerated the bike from a stop in fifth gear a few times. I also think there could be battery or bad gas issues.
|
This is one of those things which are easier said than done. To start with, let me show you a picture of a four speed transmission which has been blown apart: All of those hundreds of parts go through the front end of the transmission. If a single part is bad (which it usually is not the case), you have to pull all of this apart in order to diagnose and repair. Like the mechanic you talked to said, it doesn't make sense to replace just the part which is bad while you have it all apart. The parts are pretty much the cheap part of the rebuild (or fix). Why not just make it a brand new transmission through the rebuild process. You could replace the single part, at a cost difference of a couple hundred dollars, only to have it go bad again in the not too distant future when another part goes bad which wasn't replaced. In most cases when a transmission needs repaired, it is one or more of the soft parts which have gone bad. These include the band(s) and clutches. Usually the hard parts, like the gears, do not go bad and are reused after a thorough cleaning and inspection. You also have to consider, the transmission is very susceptible to debris. When these soft part start letting go, it can put a lot of debris through the transmission which the filter cannot keep up with. When the debris starts going around, it will damage other soft parts in the process. Soft parts also tend to wear at about the same pace (within the same group). So, not just one clutch in the clutch pack will go bad, but the entire group of them will go bad. You aren't going to replace just one clutch, you have to replace all of them. One last thing to consider here is that they sell the transmission parts as a kit (with a few exceptions). You aren't just going to buy single parts. By parts in this instance I'm talking about the soft parts ... you can usually buy hard parts separately. There is no other way, with current transmission design, for you to get at any of the parts inside the transmission ... at least the parts which make the vehicle go. The design as it is, is very compact and does the job very well. If there was any way for a mechanic to be able to get to the parts inside without going the way it does now, it wouldn't have the strength to stay together. Believe me when I say, you could be a rich man to design an automatic transmission to do as you are suggesting and still have it as compact and efficient as what is currently offered. The reason you don't see a drain plug on most automatic transmission is because when you change the fluid, you also change the filter. The exception to this is when you take it to a shop and get the transmission flushed. When they do this, they force fluid backwards through your transmission using the cooling lines. This (supposedly) cleans the filter in the process as well as completely exchanges the old fluid for new fluid (to include the torque converter - which doesn't happen when you just drop the pan). The reason for the cost, as you suggested, is because of one, the labor involved in removing the transmission from the car, and two, because not every mechanic can rebuild a transmission. To do it right takes some extra learning. You just cannot throw it together and expect it to work ... and every make/model is different. All of that costs money. Most engines, on the other hand, are pretty much the same (with a few exceptions). They are all pretty much hard parts which go together relatively easy. There are some idiosyncrasies, but for the most part, they're not a big deal. I hope this gives you a flavor for why you aren't going to see too many shops offering to repair your transmission. Again, as the mechanic said, the major part of any transmission repair is the labor for Removal & Replacement of the transmission itself.
|
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11,315 |
Sometimes while driving in the traffic, I come across a car or two which would be dripping water-like drops from its exhaust steadily in 4-5 second intervals. I tried to ask a couple of people at the local workshops; they say, and I quote, "The car is giving an amazing mileage".
And I am like, what does that water dripping mean even then? Question is: Why does the water drip? What is the source of it? And what does it signify?
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It signifies that the car is running absolutely correct. Here is the reason why: A gasoline (petrol) molecule is made up as such: C 8 H 18 (or 8 Carbon atoms and 18 Hydrogen atoms) Energy is obtained from the combustion of it by the conversion of a hydrocarbon to carbon dioxide and water. The combustion of octane follows this reaction: 2 C 8 H 18 + 25 O 2 → 16 CO 2 + 18 H 2 O Or better said, you have two of the hydrocarbon molecules along with 25 oxygen molecules, they swirl together into a mix, the spark plug ignites them, boom, and out the tail pipe comes 16 carbon dioxide molecules and 18 water molecules ... at least in a perfect world. Some cars don't put out exactly that ratio. There may be a little bit of carbon monoxide (CO), unburnt hydrocarbons (C 8 H 18 ), and/or nitrogen oxide (NO 2 ) coming out of the engine exhaust port along with the CO 2 and H 2 O. In this case, the catalytic convertor's job is to help clean these up so you can get closer to the perfect ratio described above. As described, the water coming out of the tail pipe is a natural occurrence of the combustion process. You will usually see it coming out of the tail pipe when the engine and exhaust system of the vehicle is not completely warmed up. When it does become completely warmed up, you won't see it any more, because it comes out as steam (well, you'll see it in the winter time if it's cold enough, but you get the idea).
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|
11,381 |
I just had the A/C in my car die on me again; air coming through the vents with the A/C is just as warm with it turned on as off. However, my fridge/freezer is something I've had for over 5 years and it just keeps trooping on, cooling the food fine. I've known freezers to last fine for 20+ years. I presume that both the car A/C and fridges/freezers operate on the same principle of refrigeration, and yet cars seem to need "re-gassing" every few years or the A/C will stop working. Why is this? Why can't they make car A/C as reliable as your fridge or freezer's refrigeration?
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They are not even close in comparison. Your refrigerator is a small sealed unit that averages 488 BTU, the compressor speed is controlled to operate efficiently as possible, and is designed to operate in a controlled environment. According to electricity expert Michael Bluejay, the average
refrigerator uses 488 BTUs per hour in normal use. Read more Your car Air Conditioning is about 5 Tons (60,000 BTU) at highway speeds. Yes sixty-THOUSAND BTU, not a typo. The compressor has to operate at a variety of speeds, from idle to redline, and a wildly wide range of thermal load, and temperature. The entire system has to put up with vibration and movement, and is assembled with lines that bolt or latch together which give many more points for failure.
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12,628 |
What are the different problems that can cause an engine to burn oil and in general how difficult / expensive is each one to repair? How do you diagnose each potential cause? I found this article which describes some of the problems: Why Does My Engine Use Oil I've seen three things so far: Bad Piston Rings Bad PCV Valve Guide Seals Regarding diagnosing oil consumption and smoke the above article says the following: With older vehicles this was typically accompanied with a puff of
smoke from the exhaust. With modern vehicles, the catalytic converter
usually prevents smoke. Smoke in the exhaust is vaporized by the
converter. Unfortunately, this may drastically raise the temperature
and damage the converter, over time.
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Towards the diagnosis end of things, there are some general guidelines to follow: If you are seeing smoke coming from your exhaust, what color is the smoke? If it's blue, then it's oil If it's black, it means you are running rich (too much fuel). If it's white, the car may be burning antifreeze or (quite rare) auto-trans fluid. Since it's blue smoke you are seeing, you can know that oil is the problem. What can cause oil smoke? If the smoke only comes at start-up and quickly goes away, it can be valve seals and/or valve guides. This is because while the car sits for extended periods of time, the oil has time to seep past the valve seal and collect on top of the valve (or if the valve is in the open position, it could run past and on top of the piston). When you go to start your car, the oil is then burned, giving the tell tale puff of blue smoke. COST TO FIX: There is moderate cost involved with this, depending on the vehicle/engine. If just the seals, this can be accomplished most of the time with keeping the engine mostly together and replacing the seals. Most of the cost here is labor. If the valve guides, this requires an engine tear down. Your heads will have to be taken apart and new guides installed. There is a lot more labor here and a bit more in parts. If you see smoke as you are decelerating, this too is a possible sign of valve seals and/or valve guides. This is because as you decelerate, there is a large vacuum build up within the intake tract. There is enough vacuum to pull oil past the valve seal if it's worn. COST TO FIX: Same as above. If you see smoke while accelerating, this is a sign your oil control rings are worn. These are the bottom rings used in the ring pack. When they are worn (or the cylinders are worn past tolerance), oil can flow past the rings as the piston travels down the cylinder. The oil control rings normally will scrape the cylinder of the oil, pushing it back down into the crankcase. COST TO FIX: Their fix is quite expensive, as it requires a complete engine rebuild to fix. If a PCV is bad, you normally won't see burning oil. What you'll see is seals and gaskets failing. This can cause a loss of oil (and a very dirty engine bay). It's one of those things which can sneak up on you if you aren't paying attention. While a bad PCV is not a good thing, don't look here for a reason you're seeing oil smoke coming out the tail pipe. COST TO FIX: If you catch it before it becomes an issue, it's actually quite cheap to fix ... just replace the valve. If you see leaks at seals or gaskets, your expense goes way up, but it depends on which seal or gasket is leaking. Easy to get to seals or gaskets will cost much less, because the labor is much less. The converse holds true - Labor is a determining factor here. If you are seeing blue smoke which goes away after an oil change, but slowly comes back as you get closer to your scheduled maintenance, this could be a sign you have an internal fuel leak which is thinning the oil. As the oil gets thinner it passes by the oil control rings easier, causing your vehicle to smoke. An easy way to check this is by pulling the dipstick and smelling the oil. If you smell fuel, this may be the issue. This can be caused by an injector which is stuck open, or possibly an internal failure of a fuel pressure valve which would allow the gas to escape to where it doesn't belong. COST TO FIX: Diagnosis of what is going on will take a little bit of money. This could be a very low cost fix, to a moderate cost, depending on the actual cause. If you are not seeing smoke, but you're seeing the oil drop lower and lower as time moves on, this may be a "sort of" normal oil usage in your vehicle. Take for instance my '06 Chevrolet Silverado. Its engine is an LS variant. As these engines get up in age, it is common for them to use more oil. You don't see it from the exhaust, but it uses it up, none the less. The engine still runs great and the gas mileage has stayed about the same. Your vehicle could also be losing oil via leakage (or seepage). As engines get up in mileage, this is a very common thing. If you see spots on the driveway where you park the car, this could very well be the issue. Be mindful that vehicles will loose more oil during operation than they will just sitting in your driveway. EDIT: In deference to your edit - I can see where an up-to-temperature catalytic convertor might make some difference in smoke from the tail pipe. This does not hold true, though, for start-up smoke (puff of blue smoke), as the cat is not hot enough to make a difference. It also won't make any difference once the catalyst is covered in oil suit or if there is too much oil for the cat to deal with. Sooner or later when oil gets burnt in this manner, you'll see the blue smoke. You probably have to put new cats on at that point, as well.
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12,688 |
When I went to shop for engine oil, I found many types as such: 5W-30 A5 5W-30 A1 5W-20 SAE 5W-30 10W-30 Also I see other information such as: Fully Synthetic Semi Synthetic Oil Synthetic Blend These are just subset of what I found. So, how can I choose for my car? Does it make any difference?
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If you want to know what to use for your car, follow what your vehicle manufacturer has stated. If you would like to better understand what all the gobble-de-gook means, continue reading --- Oil Originally there was crude oil . Black gold. Texas Tea. As crude oil, it is fairly much useless. It's the distillates which make up the usable parts. Crude oil is refined down to create lubricants and fuels through many different methods. This mainly happens by heating it and breaking it down into its usable components. Chemical engineers then take the oil and make it better. They will throw in additives to help it work better, to clean, and other such things we require of it. This type of oil is called regular oil or even "dino oil" (considering oil is considered to have originated from decomposing plants and animals which originated during the time of dino saurs). When you look at a dino oil, it is not very consistent. When you consider an oil grade for dino oils, think of it as an average . I was once given this visualization of dino oil molecules: .oOoo..oOOoOo...o.o. Synthetic Oil Synthetic oil is man made. Chemical engineers take base oil stock and chemically modify it to create a lubricant which is more stable than dino oil, where operating extremes (such as high performance autos or jet engines) occur. This oil is tailored to have a controlled molecular structure with predictable properties. There are many different types of synthetic oils, made many different ways. In line with the above visualization of dino oil molecules, synthetic oil molecules might look more like this: ooooooooooooooooo To this end, there are three different categories of oil products: Organic oil - Dino oil. Regular oil. Crude oil which has been boiled. Semi-Synthetic - A mix of dino oil and synthetic oil. Can also be called synthetic blend or semi-synthetic . Synthetic - Pure man-made oil (no dino oil added). Oil Standards There are several standards in the world which pertain to oil. Some of those standards are from the: Society of Automotive Engineers (SAE) European Automobile Manufacturers Association (ACEA) American Petroleum Institute (API) (NOTE: These are some main ones, but there are others). To better understand what each organization's, let's break some things down for you. Each organization has a different indicator for their oil specification. Here are the indicators for each of the three major organizations: SAE - 0W, 5W, 10W, 20W, 25w, 8**, 12**, 16**, 20, 30, 40, 50, 60 (NOTE: ** New SAE Standard) ACEA - A1/B1, A3/B3, A3/B4, A5/B5, C1, C2, C3, C4, E4, E6, E7, D9 API - GF-6B, GF-6A, SP, SN, SM, SL, SJ, SH, SG, SF, SE, SD, SC, SB, SA, CJ-4, CI-4 Plus, CI-4, CH-4, CG-4, CF-2, CF, CF-4, CE, CD-II, CD, CC, CB, CA This is called the API Donut. It has two of these three service ratings listed in them and also tells whether an oil is considered "Energy Conserving": NOTE1: These standards can best be understood by reading through the standards body write-ups, but I will try to give a brief overview of what is important, as well as some charts which will describe them a little better than I can with a wall-of-words in this article. NOTE2: This write-up is for motor oil. Do not confuse this with how gear or other oil is labeled, because it has a completely different standard, though some of the markings appear in the same configuration. I'll start with SAE because it is probably the most confusing. SAE All of SAE specifications have to do with the viscosity of an oil. The viscosity meaning, what is the specific flow rate, at a specific temperature, through a specific sized orifice . There are two basic types of oil concerned when you are looking at the SAE specification. There is straight weight and multi-viscosity . Straight weight oil does not contain modifiers which affect how the oil flows. It is denoted by a single number such as 30. A multi-viscosity will have different flow properties depending on the temperature. It is denoted by a hyphenated number, such as 0W-20. NOTE3: Do not think of oil viscosity numbers in terms of thicker or thinner ... Flow rate is modified by means other than the how thick or thin it is. The first number of the two has a "W" following it. This indicates the Winter or cold start viscosity of the oil (though some mistakenly think the "W" stands for "weight"). Originally this denoted the viscosity of oil when it is measured at 0degF. In 1999 this was changed due to an outbreak of engine failure due to oil jelling at low temperatures (see chart below for newer standard). The second number denotes the viscosity of the oil when measured at 100degC (or 212degF). This chart indicates some numbers which may or may not be useful to the average Joe, but are the specification for each of the numbers I've listed (other than 8**, 12**, & 16** which are newer SAE oil specifications): You will notice that the for each of the Winter designations, it is mainly concerned with how well the oil flows at a given minimum temperature . Whereas the straight number has concerns on both the minimum and maximum flow rate of an oil. NOTE4: 100degC (or 212degF) is used as a main reference point due to this being the approximate running temperature of an engine. It is an easy reference point to work with. NOTE5: Please understand that a 5W-30 and 10W-30 are still 30 grade oils and will still perform the same at a higher given temperature. The difference is their flow rate is different at the lower temperatures. This is achieved through molecular chains which open (become straight) and close (bunch up) at different temperatures. This opening and closing effect changes how the oil flows and thus effectively changes the viscosity without changing the oil grade itself. Here is a general chart of which oil should be used in which temperature range (though it is my personal belief you should follow what your vehicle manufacturer's recommendation so as to not void warranties, etc): Some vehicle manufacturers will give you a variance chart in your owner's manual which tells you which weight to use if you sustain higher or lower temperatures during the year. ACEA The ACEA is a little easier to figure out than SAE. Their standards are broken down into three main areas: A/B; C; and E. A/B : Gasoline (petrol) and Diesel Engine Oils C : Catalyst Compatibility Oils E : Heavy Duty Diesel Engine Oils Here is the write-up I pulled from this website which explains each of the individual specifications. Each of the following is a current specification: A1/B1 Stable, stay-in-grade oil intended for use at extended drain intervals in gasoline engines and car & light van diesel engines specifically designed to be capable of using low friction low viscosity oils with a high temperature / high shear rate viscosity of 2.6 mPa*s for xW/20 and 2.9 to 3.5 mPa.s for all other viscosity grades. These oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt. A3/B3 Stable, stay-in-grade oil intended for use in high performance gasoline engines and car & light van diesel engines and/or for extended drain intervals where specified by the engine manufacturer, and/or for year-round use of low viscosity oils, and/or for severe operating conditions as defined by the engine manufacturer. A3/B4 Stable, stay-in-grade oil intended for use in high performance gasoline and direct injection diesel engines, but also suitable for applications described under A3/B3. A5/B5 Stable, stay-in-grade oil intended for use at extended drain intervals in high performance gasoline engines and car & light van diesel engines designed to be capable of using low friction low viscosity oils with a High temperature / High shear rate (HTHS) viscosity of 2.9 to 3.5 mPa.s. These oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt. C1 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines requiring low friction, low viscosity, low SAPS oils with a minimum HTHS viscosity of 2.9 mPa.s. These oils will increase the DPF and TWC life and maintain the vehicles fuel economy. Warning: these oils have the lowest SAPS limits and are unsuitable for use in some engines. Consult owner manual or handbook if in doubt. C2 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines designed to be capable of using low friction, low viscosity oils with a minimum HTHS viscosity of 2.9mPa.s. These oils will increase the DPF and TWC life and maintain the vehicles fuel economy. Warning: these oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt. C3 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines, with a minimum HTHS viscosity of 3.5mPa.s. These oils will increase the DPF and TWC life. Warning: these oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt. C4 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines requiring low SAPS oil with a minimum HTHS viscosity of 3.5mPa.s. These oils will increase the DPF and TWC life. Warning: these oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt. C5 Stable, stay-in-grade Engine Oil with Mid SAPS-Level, for further improved Fuel Economy, intended for use as catalyst compatible Oil at extended Drain Intervals in Vehicles with all Types of modern Aftertreatment Systems and High Performance Passenger Car & Light Duty Van Gasoline & DI Diesel Engines that are designed to be capable and OEM-approved for use of Low Viscosity Oils with a minimum HTHS Viscosity of 2.6 mPa.s. E4 Stable, stay-in-grade oil providing excellent control of piston cleanliness, wear, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under very severe conditions, e.g. significantly extended oil drain intervals according to the manufacturer's recommendations. It is suitable for engines without particulate filters, and for some EGR engines and some engines fitted with SCR NOx reduction systems. However, recommendations may differ between engine manufacturers so Driver Manuals and/or Dealers shall be consulted if in doubt. E6 Stable, stay-in-grade oil providing excellent control of piston cleanliness, wear, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under very severe conditions, e.g. significantly extended oil drain intervals according to the manufacturer's recommendations. It is suitable for EGR engines, with or without particulate filters, and for engines fitted with SCR NOx reduction systems. E6 quality is strongly recommended for engines fitted with particulate filters and is designed for use in combination with low sulphur diesel fuel. However, recommendations may differ between engine manufacturers so Driver Manuals and/or Dealers shall be consulted if in doubt. E7 Stable, stay-in-grade oil providing effective control with respect to piston cleanliness and bore polishing. It further provides excellent wear control, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under severe conditions, e.g. extended oil drain intervals according to the manufacturer's recommendations. It is suitable for engines without particulate filters, and for most EGR engines and most engines fitted with SCR NOx reduction systems. However, recommendations may differ between engine manufacturers so Driver Manuals and/or Dealers shall be consulted if in doubt. E9 Stable, stay-in-grade oil providing effective control with respect to piston cleanliness and bore polishing. It further provides excellent wear control, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under severe conditions, e.g. extended oil drain intervals according to the manufacturer's recommendations. It is suitable for engines with or without particulate filters, and for most EGR engines and for most engines fitted with SCR NOx reduction systems. E9 is strongly recommended for engines fitted with particulate filters and is designed for use in combination with low sulphur diesel fuel. However, recommendations may differ between engine manufacturers so Drivers Manuals and/or Dealers should be consulted if in doubt. And finally ... API The API has two distinct categories. Those for gasoline engines ( S designation) and for diesel engines ( C designation). I am only going to give you the write-ups for those specifications which are current. You can look where I pulled them from to get the rest if you are so inclined: GF-6A Introduced in May 2020 designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, improved high temperature deposit protection for pistons and turbochargers, more stringent sludge and varnish control, improved fuel economy, enhanced emission control system protection and protection of engines operating on ethanol-containing fuels up to E85. GF-6B *Introduced in May 2020, applies only to oils having an SAE viscosity grade of 0W-16, designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, high temperature deposit protection for pistons and turbochargers, stringent sludge and varnish control, improved fuel economy, emission control system protection and protection of engines operating on ethanol-containing fuels up to E85. SP Introduced in May 2020 designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, improved high temperature deposit protection for pistons and turbochargers, and more stringent sludge and varnish control. API SP with Resource Conserving matches ILSAC GF-6A by combining API SP performance with improved fuel economy, emission control system protection and protection of engines operating on ethanol-containing fuels up to E85. SN Introduced in October 2010 Introduced in October 2010 for 2011 and older vehicles, designed to provide improved high temperature deposit protection for pistons, more stringent sludge control, and seal compatibility. API SN with Resource Conservingmatches ILSAC GF-5 by combining API SN performance with improved fuel economy, turbocharger protection, emission control systemcompatibility, and protection of engines operating on ethanol-containing fuels up to E85. SM Introduced on 30 November 2004 Category SM oils are designed to provide improved oxidation resistance, improved deposit protection, better wear protection, and better low-temperature performance over the life of the oil. Some SM oils may also meet the latest ILSAC specification and/or qualify as Energy Conserving. They may be used where API Service Category SJ and SL earlier categories are recommended. SL 2001 Gasoline Engine Service Category SL was adopted to describe engine oils for use in 2001. It is for use in service typical of gasoline engines in present and earlier passenger cars, sports utility vehicles, vans and light trucks operating under vehicle manufacturers recommended maintenance procedures. Oils meeting API SL requirements have been tested according to the American Chemistry Council (ACC) Product Approval Code of Practice and may utilize the API Base Oil Interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SJ and earlier categories are recommended. SJ 1997 Gasoline Engine Service Category SJ was adopted in 1996 to describe engine oil first mandated in 1997. It is for use in service typical of gasoline engines in present and earlier passenger cars, vans, and light trucks operating under manufacturers recommended maintenance procedures. Oils meeting API SH requirements have been tested according to the American Chemistry Council (ACC) Product Approval Code of Practice and may utilize the API Base Oil Interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SH and earlier categories are recommended. FA-4 API Service Category FA-4 describes certain XW-30 oils specifically formulated for use in select high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway greenhouse gas (GHG) emission standards. These oils are formulated for use in on-highway applications with diesel fuel sulfur content up to 15 ppm (0.0015% by weight). Refer to individual engine manufacturer recommendations regarding compatibility with API FA-4 oils. These oils are blended to a high temperature high shear (HTHS) viscosity range of 2.9cP–3.2cP to assist in reducing GHG emissions. These oils are especially effective at sustaining emission control system durability where particulate filters and other advanced aftertreatment systems are used. API FA-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties, and soot-related viscosity increase. API FA-4 oils are not interchangeable or backward compatible with API CK-4, CJ-4, CI-4 with CI-4 PLUS, CI-4, and CH-4 oils. Refer to engine manufacturer recommendations to determine if API FA-4 oils are suitable for use. API FA-4 oils are not recommended for use with fuels having greater than 15 ppm sulfur. For fuels with sulfur content greater than 15 ppm, refer to engine manufacturer recommendations. CK-4 Current - 2017 API Service Category CK-4 describes oils for use in high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway and Tier 4 non-road exhaust emission standards as well as for previous model year diesel engines. These oils are formulated for use in all applications with diesel fuels ranging in sulfur content up to 500 ppm (0.05% by weight). However, the use of these oils with greater than 15 ppm (0.0015% by weight) sulfur fuel may impact exhaust aftertreatment system durability and/or oil drain interval. These oils are especially effective at sustaining emission control system durability where particulate filters and other advanced aftertreatment systems are used. API CK-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties, and soot-related viscosity increase. API CK-4 oils exceed the performance criteria of API CJ-4, CI-4 with CI-4 PLUS, CI-4, and CH-4 and can effectively lubricate engines calling for those API Service Categories. When using CK-4 oil with higher than 15 ppm sulfur fuel, consult the engine manufacturer for service interval recommendations. CJ-4 Current - 2006 Introduced in 2006 for high-speed four-stroke engines. Designed to meet 2007 on-highway exhaust emission standards. CJ-4 oils are compounded for use in all applications with diesel fuels ranging in sulphur content up to 500ppm (0.05% by weight). However, use of these oils with greater than 15ppm sulfur fuel may impact exhaust after treatment system durability and/or oil drain intervals. CJ-4 oils are effective at sustaining emission control system durability where particulate filters and other advanced after treatment systems are used. CJ-4 oils exceed the performance criteria of CF-4, C-4, AH-4 and C-4. CI-4 Plus Current - 2004 Used in conjunction with API C-4, the " CI-4 PLUS" designation identifies oils formulated to provide a higher level of protection against soot-related viscosity increase and viscosity loss due to shear in diesel engines. Like Energy Conserving, CI-4 PLUS appears in the lower portion of the API Service Symbol "Donut." CI-4 Severe-Duty Diesel Engine Service The CI-4 performance requirements describe oils for use in those high speed, four-stroke cycle diesel engines designed to meet 2004 exhaust emission standards, to be implemented October 2002. These oils are compounded for use in all applications with diesel fuels ranging in sulfur content up to 0.05% by weight. These oils are especially effective at sustaining engine durability where Exhaust Gas Recirculation (EGR) and other exhaust emission componentry may be used. Optimum protection is provided for control of corrosive wear tendencies, low and high temperature stability, soot handling properties, piston deposit control, valve train wear, oxidative thickening, foaming and viscosity loss due to shear. CI-4 oils are superior in performance to those meeting API CH-4, CG-4 and CF-4 and can effectively lubricate engines calling for those API Service Categories. CH-4 Severe-Duty Diesel Engine Service This service oils are suitable for high speed, four-stroke diesel engines designed to meet 1998 exhaust emission standards and are specifically compounded for use with diesel fuels ranging in sulfur content up to 0.5% weight. CH-4 oils are superior in performance to those meeting API CF-4 and API CG-4 and can effectively lubricate engines calling for those API Service Categories. NOTE6 : A lot of this data you will never need to know. I have placed it here for future reference. I can see this being updated over time as new standards are brought to bear.
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15,588 |
I have been driving stick for 15 years and within the last year I learned I can shift gear without the clutch. Normally the transmission will not let me shift gears without using the clutch. However, if I hit the right RPM, my stick will let me shift into the new gear without any resistance. Why does this work and is there a downside?
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You can do this if your engine RPM, the speed of the vehicle, and the gear you are shifting to/from is just right. The reason you can do this is because you have synchros in the transmission which allows the two gears to match rotational speeds as they come in contact (basically, there is more to it than this, but hopefully you get the drift). The synchros are sacrificial in that as they are designed to wear out before the gears get worn. When you perform clutchless shifting, you are creating a large amount of unneeded wear on your synchros. By wearing these out, you'll be required to rebuild your transmission sooner than by utilizing normal shifting methods. With the clutchless method you are using, you are causing these the synchros to attempt to mesh until the correct rpm is met, even if it is for a short period of time. This is where the wear will occur. Even if it is a short period of time, there is just about no way you can hit this exact every time . If you feel that you are, you are more than likely fooling yourself. Any resistance during the shift is unneeded wear on the synchros.
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17,490 |
When we are using a turbocharger to compress the incoming air, the air gets hotter. Usually this hot air is cooled by using an intercooler before it's passed to the engine. What is the reason behind cooling this air? Why can't we pass it as hot air, since inside the engine the air will be compressed which will heat it up anyway?
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tl;dr To combat detonation (in SI engines) To increase power/efficiency Details There are a few important factors at play here. Engine detonation is a real concern for SI engines A spark-ignition engine is more likely to experience premature ignition (aka knocking or detonation) with hotter air. In fact, the calculations in the example below can show that this is the primary reason why intercooling is such a Good Idea. Hot air rises, cold air sinks In physics-speak, hot air is less dense than cold air. This means that the volume occupied by 1 kg of hot air is greater than the volume occupied by 1 kg of cold air. The internal combustion engine is a volumetric device What this implies is that every time the engine turns over and completes a cycle, the volume of air that is admitted into the combustion chamber(s) is fixed. Power depends on mass, not volume The power developed by the engine is proportional to the mass of air admitted into the combustion chamber and not its volume. More air molecules = more bang. The reason why turbochargers (or any other forced-induction devices) are utilized is to increase the power and/or efficiency of the IC engine. At combustion chamber level, this is achieved by increasing the amount of air molecules present during combustion. The turbocharger achieves this by pressurizing the incoming air. An unwanted by-product of this compression process is that the outgoing air is hot and less dense. If this hot air is fed to the combustion chamber as-is, the likelihood of engine detonation is greater. By cooling the air via an intercooler, engine operation being safer since engine knock is reduced. As an added bonus the air becomes slightly denser, enabling more air molecules to be present during combustion. Bonus Example This is one of those questions where numbers can speak louder than words : Forums indicate that a stock Mitsubishi Evo X is capable of generating 22 psi boost at mid-range RPM. At sea level, the turbo inlet conditions are as follows: Air pressure @ turbo inlet = 14.7 psi
Assumed inlet air temperature = 25 °C
=> air density @ turbo inlet = 1.184 kg/m^3 Assuming 85% turbocharger efficiency, engineering calculations 1 will yield a discharge temperature close to 92 °C: Air pressure @ turbo outlet = 14.7 + 22
= 36.7 psi
Air density @ 36.7 psi, 92 °C = 2.41 kg/m^3 Were it not for the fact that we care about detonation, the outlet density value looks rather tasty - it is more than double that of the inlet. But look what happens when we run this hot discharge air through an intercooler. Let's assume a 1 psi drop in pressure, and that the air is cooled down to 70 °C: Air density @ 35.7 psi, 70 °C = 2.50 kg/m^3 Despite the fact that we lose precious boost through the intercooler, the cooling effect ends up increasing the density by over 3%, so now the air is denser, and, more importantly, safer from an engine knock/detonation standpoint. 1 - I have worked out a truly marvelous calculation for this, which this margin is too narrow to contain
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|
18,292 |
I* hit a curb and got a small tear in the front passenger side tire. The tear is about 1" long and goes mostly across the surface of the tire but also a little bit, maybe 1/4", toward the inside of the tire. If this is beyond cosmetic and not repairable, I'll of course replace the tire. But these tires only have about 3000 miles on them and to my uneducated eyes, this area of the tire looks like a rubber ridge designed for style or rim protection rather than structure. Not that the rim protection worked! These are BF Goodrich Advantage T/A tires, size 225/50R17, in case that matters. * OK, it was my wife driving at the time, but I'd never blame her in public!
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The damage you are showing is minor cosmetic damage. If the following occurs with sidewall damage, then get it replaced: Tire deflation (cannot be legally repaired in most countries) You pull the flap back and see damage to the side wall plies (corded area under the rubber which supports the tire) whether deflation has occurred or not Bulging of the tire at the damage site If you aren't seeing any of these things, you should not have any issues running your tire until the tread wears out (normal use). As a side note (and primarily my opinion with nothing to really back it up), the area where your damage has occurred seems to be extra rubber put in place on low profile tires to help protect the rims from curb rash. Yours looks like it was a little more serious of a curb encounter, but still, if no issues as stated above, you should be fine. EDIT: If the flap of rubber sticking out bothers you (aesthetically), use a small amount of rubber cement to it and it should keep it in place. It really isn't bothering anything the way it is.
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|
21,048 |
What is a rod knock? What causes a rod knock, how bad is a knocking rod, and how can I tell if a rod is knocking?
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To get to basics, the rod (or connecting rod ) is the portion of the engine which connects the piston to the crankshaft. Where the rod connects to the crankshaft there is a bearing which separates the rod itself from the crank journal. The bearing is made from a softer material than the rod or the crankshaft. You can see most all of the internal parts of an engine in this exploded view below. The connecting rod is #7, the crank shaft is #16, piston #4, and bearing can be found marked as #8. When an engine is built, there are certain gap tolerances (specific distance measured in .001") which are built into it, the rod bearing to crankshaft journal being no different. In this case, the tolerance is there to allow a specific amount of oil through from a hole in the crankshaft journal and remain on the bearing surface. Oil films on the bearing and keeps the two parts from touching during normal engine operation. If the clearance gets too big from either wear or deformation, the oil will no longer film correctly and you will get the rod knock . The noise itself occurs due to metal on metal contact between the bearing and the crankshaft journal during the power stroke of the engine cycle. If the situation is really bad it can even be caused by the rod itself contacting the crankshaft journal (where the bearing has become out of place). The most common cause of rod knock is due to a spun bearing (bearing itself actually spins in the end of the rod so it becomes out of position). This usually happens due to rod cap stretch during abusive driving situations. It can also happen due to a lack of lubrication, either because of a lack of oil or because oil is flowing incorrectly. It can also be caused by a combination of any (or all) of the three. A rod knock is a very serious issue with the engine. As you can probably tell from my write-up, it means the engine is no longer functioning correctly. It is the death knell of the engine. Once the rod knock occurs, it will not cure itself. The rod bearing must either be replaced along with fixing associated parts (you don't usually replace just one rod bearing as the entire engine would need rebuilt at that point), or the engine will need to be replaced. A rod knock is as described ... A low pitched knocking sound which can be heard low in the engine. It will increase in frequency as the engine speeds up, but can usually be heard at any engine speed. If you hear a knocking sound which seems to disappear after the engine warms up, it's probably not a rod knock. It may be something as innocuous as a leaking exhaust gasket. If you believe you have a rod knock, you should seek a second opinion from a trusted mechanic. A rod knock is an expensive fix, so you need to make sure of what it is prior to diving in head first.
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|
23,865 |
I have always wondered why heavy vehicles such as large trucks and buses almost always use diesel engines, whereas in light cars there is a choice between diesel and gasoline engines. Engine efficiency might explain the preference towards diesel engines, but then again isn't this a valid consideration also in light cars? You should get better efficiency with a diesel engine, and therefore, all cars should use diesel engines. So, why do large vehicles almost always use diesel engines, but light cars have a choice between gasoline and diesel? Could modern technology such as hybrid technology with Atkinson cycle bring gasoline engines to large vehicles as well? I have read that the Atkinson cycle engine in 2016 Toyota Prius has 40% thermal efficiency. This is very diesel-like in my opinion and if the technology is scaled up, could help bring gasoline technology to large vehicles.
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Torque is the name of the game. High torque is needed to move heavy loads. If comparing a gasoline engine to a comparable diesel engine the diesel will always have higher torque. The higher torque comes from the need for a higher compressing ratio needed for compression ignition. To achieve the higher compression ratio a longer stroke is required. The longer stroke comes from a greater crankshaft offset. This offset gives greater torque. Another aspect is that diesels can make tremendous torque at very low RPM. Very simply put more fuel equals more torque when everything else is kept the same. A diesel does not have throttle plates and draws in the maximum amount of air on every stroke. In a diesel the amount of fuel added is what controls the power. The throttle controls how much fuel is added. This means that a diesel always runs lean. At idle the engine uses hardly any fuel. This lean mixture allows for the addition of large quantities of fuel even at low RPM. A gasoline engine on the other hand always has to keep the fuel mixture at optimal stoichiometric. This need to keep the mixture correct means that to get more fuel the engine needs to rev to higher RPMs. This means that a gasoline engine makes it's torque at much higher RPM than a diesel. This high end torque characteristic makes a gasoline engine hard to drive necessitating constantly keeping the RPM high. The only real draw back to this torque production is a limited RPM. This is compensated by a gear box with lots and lots of gears. If a gasoline engine was used it would have to be much larger. The much larger engine would make for greater fuel consumption.
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24,323 |
On my VW Passat B5 tires, there is a marking that reads "195/65R15 91 V". What does this mean? Do I have to get replacement tires with this exact marking on the side of the tire in the future or not? And if not, how can it differ? EDIT Not a duplicate as the other question is incomplete as it just tells the size, this covers the other markings too and gives more in depth, complete answers.
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The tyre code is as follows: An optional letter indicating the intended vehicle class. Your tyre doesn't have one (or you omitted it) but it should be a P for passenger car. Possible values are: P for Passenger Car LT for Light Truck ST for Special Trailer T for Temporary Digits before the slash indicate the tyre width in millimetres. Your tyre has a width of 195 millimetres, which is a little over 7½ inches. Digits after the slash indicate the height of the sidewall as a percentage of the width. Your tyre has a sidewall height of 65% × 195 millimetres which equals 126.75 millimetres or about 5 inches. The letter after that indicates the type of tyre. Your tyre is an R for radial. Possible values are: B for Bias Belt D for Diagonal R for Radial If omitted, it's a cross-ply The digits directly after that letter indicate the diameter of the rim in inches . Your tyre is mounted on a 15 inch rim. The digits after the space are the load index. Your tyre is rated for a load up to 615 kilogrammes (1,356 lb), which is per tyre . Assuming four tyres, that comes to a maximum total weight of 2460 kilogrammes of your car plus everything in and on it. Possible values range from 60 for 250 kg / 550 lb to 125 for 1,650 kg / 3640 lb. The letter after that is the speed rating. Your tyre is rated V for speeds up to 240 km/h (149 mph). Possible values are: A1 for 5 km/h / 3 mph A2 for 10 km/h / 6 mph A3 for 15 km/h / 9 mph A4 for 20 km/h / 12 mph A5 for 25 km/h / 16 mph A6 for 30 km/h / 19 mph A7 for 35 km/h / 22 mph A8 for 40 km/h / 25 mph B for 50 km/h / 31 mph C for 60 km/h / 37 mph D for 65 km/h / 40 mph E for 70 km/h / 43 mph F for 80 km/h / 50 mph G for 90 km/h / 56 mph J for 100 km/h / 62 mph K for 110 km/h / 68 mph L for 120 km/h / 75 mph M for 130 km/h / 81 mph N for 140 km/h / 87 mph P for 150 km/h / 94 mph Q for 160 km/h / 100 mph R for 170 km/h / 106 mph S for 180 km/h / 112 mph T for 190 km/h / 118 mph U for 200 km/h / 124 mph H for 210 km/h / 130 mph V for 240 km/h / 149 mph Z for over 240 km/h / over 149 mph W for 270 km/h / 168 mph (W) for over 270 km/h / over 168 mph Y for 300 km/h / 186 mph (Y) for over 300 km/h / over 186 mph
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24,327 |
Fans that look like this: Is it to somehow help the balance of the engine?
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It isn't something restricted to old vehicles; my Lumina has fans like this, though not as irregular as the picture shown in the question. As far as I can recall, the chief reason cited for this by the manufacturer is noise reduction . You'll notice the additional weight on some of the blades to ensure that rotational balance is maintained despite the asymmetry.
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24,514 |
The "Service Engine Soon" light came on yesterday and isn't going away on its own. The car drives fine, no weird noises, smells, or other symptoms. The manual is not very helpful, just directing me to take it to a professional for service. Before I do that, I'd like to try and eliminate any possible causes that are easy to check for myself. The specific car I'm working with is a 2002 Nissan Maxima that passed smog two weeks ago, but I'm interested in general advice too. I'm comfortable changing oil and filters but not much more. My tools are limited to a pair of jack stands, oil pan, and a wrench and socket set. I would prefer not to invest in new tools unless they are going to be useful again and again. What are some of the possible causes for the "check engine" light that can be diagnosed at home? Where should I start?
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You've come to the right place. There's a lot that you can do on your own. Even if all you end up doing is gathering more information for the mechanic who ends up working on the car, they never mind a hint as to where the problems might be! What are some of the possible causes for the "check engine" light that
can be diagnosed at home? All of them. They can be all over the map, ranging from things as simple as "the gas cap is loose" to "major engine parts have broken off." Where should I start? You should start with a tool that will help you determine what the singularly unhelpful check engine light is actually trying to tell you: a code reader . A code reader will query the engine computer to see what's on its mind. The engine computer will respond with a series of codes (from one to an arbitrary number of them), each of which will stand for a short diagnostic message. Depending on the tool that you use, you might also get a paragraph description and background information to go along with the code. Some tools will even let you clear out a code to see if it comes back (much like rebooting your PC to see if the problem goes away). If the tool doesn't give you much more than some letters and numbers, try typing the results into the search box in the upper right of this page. There is a 100% chance that you are not the first person to have a particular problem and some of those people have come here with the same question. For example, I've had a P0420 code on my wife's old Outback. That lead me to conclude that one of the O2 sensors in the exhaust system was going bad. A little cash and a fair amount of annoying wrench work and the problem was solved. If searching isn't helpful enough, come back with a new question letting us know the make and model of your car, the codes that you've found and any other symptoms that you've observed. This is a place where car nerds will happily help you for the fun of it! PS: I just ran across Lynn's answer to the question What CAN'T the check engine light tell you? Lynn gives provides some links to the Wikipedia list of OBD codes as well as some examples of where those codes might lead you in diagnosis.
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24,555 |
When a car is topped up with oil, it clear to most people that you are supposed to fill it to the recommended amount as specified by the manufacturer (normally on a dip stick). What exactly are all of the disadvantages to running an engine when the oil becomes too low?
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Engine oil does much more for an engine than lubricate. It provides cooling, cleaning, and a bunch of other chores. You already know engine function is degraded when you run out of oil. Let's see if we can run it down to make more sense for you how it happens. Let's say, for lack of argument, your engine is running with very little to no oil. The engine oil light is on as the engine is running. Antifreeze is up to snuff, but that won't stop overheating for too long. Here is what happens: As whatever limited oil is in the engine is pushed around, it becomes hotter and hotter. It becomes hotter because the oil isn't allowed enough time to cool down a little before it is required to go back into the engine and do its thing. As this happens, the oil will wear out faster. Fully synthetic oil will last longer than dino (refined) oil, but it will suffer defeat sooner or later as well. Several reactions happen to the oil, to include oxidation, thermal degradation, and compressive heating. Mind you, all of these things are created under normal use conditions (and thus the reason we change oils when we should), but under extreme conditions as you've suggested, it all happens much faster . This is a great image which describes what happens from the Machinery Lubrication website - All of this breakdown creates the regular: tar; sludge; varnish; soot; etc. All of these things start depositing on the internals of your engine, such as the rings, bearings, cylinder walls ... anywhere oil would normally flow. If you go back to your chemistry teachings, you'll probably remember that a large portion of oil is carbon. All of the previously mentioned nasty substances are actually a carbon byproducts. As these carbon substances continue to deposit, any part which comes in contact with them gets wear on them as carbon can become quite hard and/or sticky under the right circumstances. This starts creating more friction on these parts. So now instead of cooling/lubricating/cleaning, the oil has broken down is now heating (due to more friction), creating deposits, and making the engine a really filthy place . You should realize it is now doing everything it was originally meant to replace. Every machined surface within the engine is susceptible to the increased wear. As the oil continues to break down at an ever increasing rate, the temperature inside the engine on these machines surfaces continue to get hotter and hotter. Wear occurs faster and faster until something gives. Most of the times in these situations, the first thing to go is a rod or main bearing. If the backside of the rod bearing is strong enough when this happens, you can throw a rod. Throwing a rod is basically where the friction on the bearing at the rod journal of the crankshaft is strong enough to overcome the strength of the rod itself and it has a catastrophic plastic deformation of the metal. The piston can go down the bore and will not return. It can go out the bottom and then gets flung around inside of the oil pan, or the rod itself will break and force itself and/or the piston out the side of the engine block. At this point, there is no coming back from it (in most cases). The engine is done and will need to be replaced. If you continue to run the engine with very low oil, destruction will occur ... and no ... I'm not being melodramatic about it. EDIT: Here are a couple of videos which describe what happens when you don't change the oil in your vehicle. This is what happens with oil when there isn't enough of it ... with lack of oil, it doesn't take 130k miles to look like this. https://youtu.be/KC-SxrsgEwo https://youtu.be/oIkxlWpJ6bk
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24,719 |
I need to jack up my car to take out the front driver side tire and change the p/s and alternator belt. I don't own a floor jack but I do have a scissor jack. I was wondering could I just use the scissor jack instead of the floor jack to raise the car up and lower it on the jack stand. I have a chock too. I know the floor jack adds more protection because it can be slightly raised up again so in case the jack stand gives out. This is if it is my first time using a jack. Thank you.
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You can use either jack you want For safety sake, don't get under the car unless you have some jackstands. It isn't the jack failing that kills you. It's the fact that you only used a jack and didn't have any backup. You NEVER use a jack alone if you are getting underneath the car. You ONLY use a jack to change a tire on the side of the road and you never get underneath your car without jack stands in that situation...NEVER you never get underneath your car without jack stands in that situation...NEVER you never get underneath your car without jack stands in that situation...NEVER If you don't have access to jackstands, take the spare tire off your car and jam it up under the car. If it doesn't take up enough space, don't get under. Do these things Put the car in park Use the emergency brake Find anything you can to use as wheel chocks. 2x4 is better than a rock. A rock can skid along smooth concrete if you are on a slope. Don't jack up the car if it's on a slope, no matter what. Especially since your are a 'jack your car up virgin' Put the car on level ground Use jack stands Use jack stands Use jack stands If you don't have jackstands, use two of your wheels. The spare and another off the car. Jam them up in there. Make sure the car won't fall more than an inch Make sure you jack your car up per your owners manual. Get it out of the glove box and open it. It will tell you where to place your jack. BE SAFE, BE SAFE, BE SAFE, BE SAFE, BE SAFE If you feel uncertain, don't do it. Ask a neighbor who has done it before to help you. Call your friends. Have them come over and help you. Have someone with you in case something happens and you need help. Do not do this alone since it is your first time. Don't do it alone. DO NOT DO IT ALONE. Have your GF/Wife there. Anybody. The moment you feel uncomfortable abandon the project and find someone to assist. This post makes me incredibly nervous because you have not done this before. Please be safe. Edit: Your jack placement is very important. If you place your jack incorrectly it can damage your car. I already said this piece but get the owners manual out of your glovebox. It will tell you EXACTLY where to place your jack. There are points the manufacturer designed into the car for you to jack it up. You will want to use those hardened jack points.
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24,778 |
My 2013 Subaru WRX has a 5-speed manual, and I long for it to have a 6th gear when cruising on the highway. A friend has a 2012 Subaru STI with a 6-speed manual, and I noticed his car runs through the gears more quickly to achieve the same speeds. At 3300-3500 RPMs, shouldn't the WRX be able to achieve better gas mileage by keeping the same 5-speed gear ratios, while adding an additional gear to lower RPMs to 2800-3000?
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tl;dr: different gear ratios are a feature, not a bug. Some cars use more gears for acceleration, some use them for better gas mileage. You can't do both. At 3300-3500 RPMs, shouldn't the WRX be able to achieve better gas mileage by keeping the same 5-speed gear ratios, while adding an additional gear to lower RPMs to 2800-3000? You've exposed the classic trade off in transmissions. We want to get the spinning motion of the motor to turn into spinning motion of the wheels. Unfortunately, the engine has a maximum rotational speed (the redline is there for a reason). The gears in the transmission are really just multipliers in the rotational velocity equation. First, a picture: In this image, you can see that the larger gear A (being driven by the motor) is driving the smaller gear B (used to turn the wheels). Yes, I know that there are more bits after this gear but for the sake of discussion let's forget final drives, etc. In this example, you can see that each turn of gear A results in two turns of gear B. This translates to a gear ratio of 1:2 or 0.5. If you had this gear in your car, you could cruise at very low revs on the highway (but you'd never get up a hill!). Saying it again, in words: A low ratio gear will turn the car tires a low number of times for each engine rotation. A high ratio will turn the car times several times per engine rotation. Thus, a high gear ratio at the top end permits a high top speed. It also means that, at highway speeds, the engine revolves less per linear meter of road. Fewer revs == less gasoline burned per second. Note: sometimes you will about hear "short" and "tall" gears. Short gears are the low speed gears (with high ratios) and tall gears are for high speeds (with low ratios). This inversion of terminology is one of the great joys of trying to discuss transmissions. However, a high gear ratio has a lower mechanical advantage. This means that it's harder to accelerate the vehicle (tires have to turn faster to get the car to go faster). A fuel efficient gear ratio is also not a fun gear ratio (less zip). When you really want to accelerate quickly, adding gear ratios down low (say a six speed rather than a five speed) lets you stay at a higher mechanical advantage for longer. However, if you're focused on fuel efficiency, you can also take what is effectively a five speed and put a really low gear up top for highway cruising. This will get your mpg numbers up but will be extremely non fun (you might even be below the minimum revs required to spin up the turbo). Back to the specific cars in question: From looking at the WRX vs STI gear ratios, it's clear that the WRX has a low ratio first and second gear so that you only have to shift once to reach 60 mph. This is purely an effort to optimize the 0-60 time (marketing. Sigh). In the STI six speed, the gear ratios of the first five gears are spaced pretty evenly between the gear ratios of the first four of the WRX. This means that the STI won't feel that slog through first and second that we five speeders have to labor through. Even the sixth gear of the STI is still a higher ratio than the fifth gear of the WRX. Cruising won't be as relaxed but you'll be better able to accelerate from 50 mph to some higher number....
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25,089 |
I have an older engine that is seized. It is a 1953 Desoto Hemi. How can I un-seize it? I have sprayed Sea Foam Deep Creep down the plugs and let sit for weeks. As well as transmission fluid. To no avail, this bad boy won't crack. I have attempted to use a pipe wrench on the pulley, with a 10' solid steel pipe as an extension. It would not move. I suspect using a 20' extension might help the situation. There has to be a systematic approach to get this turning.
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Stop trying to crank it and start beginning to disassemble it. Something is seriously wrong with it and forcing it will only break more stuff that might not already be broken. Especially if you have no idea what caused it to seize in the first place. The only thing more annoying than a seized engine is a seized engine with a sheared off bolt in the nose of the crank. Save yourself the hassle. I would start by disconnecting the crankshaft from the camshaft and seeing if the bottom half can rotate when disconnected from the valvetrain. Looks like you've already done that so on to the next step. If that doesn't work, take off one head, try again, then take off the other. Maybe a valve and a piston hit each other really hard and are wedged together? Next, take off the oil pan and look up the cylinder bores. See anything funny? No? Remove the oil pump and remove the rods from the crank and begin pushing the rods and pistons out the top one by one. See anything funny with the bearings? The pistons? The cylinder walls? When all the rods and pistons are out, off come the main caps, the bearings and the crankshaft. Then you can start inspecting the cylinder walls and the piston skirts. This will tell you why the engine is seized. The rebuild may then commence.
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25,157 |
I'm watching a TV show called Tech Garage and they just made the claim that an engines torque and horsepower curves always meet at 5252 RPM. Assuming this is true, why does this happen? Is it something designed into engines, or is it just how the thermodynamics work out? If it is a result of design, what about the engine is arranged to make it true?
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It's just math , and is because horsepower is defined (in terms of torque) as 550 ft·lbs per second . A single HP is 33,000 pounds moved 1 foot in 1 minute (as per James Watt, that's the average of what an actual horse can do). An RPM of an engine moving the same 1 lb would travel ~6.283ft (the circumference of a 1 foot radius circle). 33,000 / 6.283 = 5252
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25,171 |
My car started fine a couple of days ago and today when I went to start it, it won't even turn over. The lights work, the battery is only a year old. Not sure where to check next. Any suggestions???
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It's just math , and is because horsepower is defined (in terms of torque) as 550 ft·lbs per second . A single HP is 33,000 pounds moved 1 foot in 1 minute (as per James Watt, that's the average of what an actual horse can do). An RPM of an engine moving the same 1 lb would travel ~6.283ft (the circumference of a 1 foot radius circle). 33,000 / 6.283 = 5252
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25,235 |
Due to this question I now have a fairly well-rounded understanding of what a head gasket is. I assumed that sometimes, when people would talk about "heads" that this was just an abbreviation of another term "head gaskets". Apparently, this is not the case! What exactly are heads? Clarification: Car heads, not human ones...
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tl dr: Cylinder heads (commonly just called "heads") are the big piece of metal which caps and seals the end of the cylinder bore. Types of Cylinder Heads: There are three basic types of cylinder heads: Flathead Cylinder Head - These cylinder heads were used on older engines such as the flat-head Ford engines (like seen below). The oval protrusion at the top of the cylinder head is for coolant flow. Coolant would flow up from the block and through passages in the head (between bolt holes) and out through this oval port at the top. Overhead Valve Head (OHV) - This type of cylinder head has been used extensively from the 1950s and are still used today. These heads have the valves located within them instead of in the block like the flathead. The valves are actuated indirectly from the cam through a valve train, which usually consists of lifters (tappets), push rods, and rocker arms. An OHV head usually looks something like these Chevrolet heads below. In the picture, the flat surface of the head (right side of the image) is the portion which faces the engine block. The left side is where you see the valve tips, valve springs, retainers, and keepers. On top of these is where you would see the rocker arms if they were installed. Overhead Cam Head (OHC) - This third type of head usually has the camshaft co-located with the cam. It is called "over head", because the cam actually resides over the top of the head. The OHC can have a single (SOHC) or dual (DOHC) configuration. (You can learn more about the differences between a SOHC and DOHC in this SE post ). Here are some images showing OHC heads: In this image, it is a little hard to see, but there is one camshaft (you can see the single gear to the left of the head) which extends the length of the head. This single cam shaft actuates both the intake and exhaust valves which are in the head. In this image of a DOHC, you can see the two cam shafts (find two gears to the right of the head in the image). with DOHC, the valves can be actuated directly (as in this image) or with the use of rocker arms. Anatomy of a Cylinder Head First let's explain the Flathead Cylinder head a little. Like I said before, it is basically just a flat chunk of metal which seals the top of the cylinder. In the image above, the top portion of the image (as I stated) is the flat part. The indentations in the head (the almost heart shaped portion) is the combustion chamber. This is where the air fuel mixture has room to burn when the piston is at top dead center (TDC) during ignition, between the compression and power cycles of an Otto cycle engine. To better understand what makes up most other cylinder heads, let's go over some of the basics (Note: some of these things were mentioned above, but I'll explain better as to what they are here): Bare Cylinder Head : This is the main building block of the entire structure. All other components we'll talk about are attached to the bare head in some form or fasion. Valve : Usually buried inside the head, this is the part which lets the air/fuel mixture into the combustion chamber and the exhaust gasses out during that portion of the Otto cycle. The valve is actuated at the precise time by the cam shaft. Here is a representative image of a valve: Valve Spring : This keeps the valve closed when it's not open. Valve springs can be comprised of one, two, or even three different spring portions (depending on the design need). Usually only very high performance engines need the spring pressures involved with three (or triple) springs. Here is a representative image of a valve spring (these are beehive springs, so called due to their shape): Valve Spring Retainer : The valve spring retainer keeps the spring located on the spring. The retainer is located on the top end of the spring (away from the head). It holds the spring in place while simultaneously attaches to the valve via retainer locks (see below). Here is a representative image of a retainer: Retainer Lock : The retainer lock (or key) is wedged between the valve tip and the retainer. An interference fit occurs because of the spring pressure pushing up on the lock, the angle of the locks in relationship to the straight stem of the valve, and the small tab which fits into the valve. Here is a representative image of a retainer lock: This is one half of a pair of locks. You can also see the angle which is created, along with the small tab which connects the lock to the valve stem. Valve Seal - The valve seal is located around the stem of the valve at the top of the valve guide (see below) underneath the valve spring. It provides a seal so as to prevent oil from leaking (or getting pumped) into the intake and exhaust tracts. Here is a representative image of a valve seal: In the image, you can see two valves (at bottom right and to the left). The valve seal is the spring which encircles the valve, the polymer piece underneath of it, and the metal which is below that. Valve Guide : The valve guide does exactly what the name implies - it guides the valve. The valve guide is a separate piece of metal usually made out of cast iron or bronze. The guide is separate from the head so as it can be replaced if needed when a head is rebuilt. It is driven into the head and provides a way to keep the valve specifically located while still allowing the valve to move up and down during the open/close cycle. There are many different types and different applications for each. Here is a representative image of different valve guides: Valve Seat : The valve seat is a hardened material which is hammered into the head, then cut at specific angles to, along with the valve, create a seal which keeps the gasses during the combustion process locked into the combustion chamber. Valve seats are usually made of some type of iron alloy as this tends to stand up to the rigors of an opening/closing valve over its lifetime. You can find seats in cast iron heads (most of the time), but you'll always find valve seats in aluminum heads. Without these, the valve would move the aluminum out of the way and would soon be damaged. Here is a representative image of a valve seat: In the image, I've added two yellow ovals. The valve seat is located between the two ovals. The seat is the portion which is discolored and looks to be machined at an angle. When the seats are place, a place is machined into the head where the seat will later be driven into it. Then the seat is cut at specific angles so the valve will make perfect contact with the seat and create a positive seal. You can also see in the image, at the center of the circles, is the valve guide peaking out at you. Spring Seat : Depending on the head manufacturer and the head design, there may also be a spring seat, which can protect the cylinder head from being galled by the spring. As you may have guessed, the spring seat straddles the valve guide and is placed between the spring and the head. You'll usually see these on aluminum heads. In this area, a manufacturer can also place valve spring shims to set the spring height correctly. Here is an image of most of the parts described above and how they all fit together (blown apart, of course): Combustion Chamber : The combustion chamber is where all the action occurs. The shape of this, in addition to the valves and dome (or dish) of the piston, shapes how the flame front travels after air/fuel ignition occurs. A combustion chamber can be of many different sizes and shapes. It all depends on what is needed for the particular engine. Below is a representative image of a big block Chevy (BBC) closed port combustion chamber. In the image, you see the face of the intake (larger valve) and exhaust (smaller valve) valves. Just to the right side of the valves (at 4 O'Clock to the valves) is a threaded hole. This is where the spark plug protrudes from. Here is a very basic OHV head. You can see the different parts of the head annotated for better understanding. All head with valves in them work fairly much the same way, but can be arranged in different ways as you've seen in the above images. Here is another image showing the cross section of how the valves, intake runner and exhaust runner may be situated within the head: Intake/Exhaust Ports : The intake and exhaust ports are the part of the head which allows the air/fuel mixture to enter the cylinder and the exhaust gasses to leave the cylinder. The size, shape, and texture of these can help or hinder how the air flow occurs. With greater flow comes greater power and torque. Here is representative image of a cutaway view of a port: Extra Bits & Pieces : During the casting of heads, coolant passages are built into them. This allows the head to bleed off excess heat from the combustion process.
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25,238 |
If your car is stuck in snow and you don't have any chains, what can be done to get it out? This can be an unnerving problem to have and it happens pretty easily with normal driving on ice. You wind up in a snowbank sliding into it at 10 mph or any number of scenarios. What are some tools I can carry with me to help me get out of snow? What are some methods I can employ to make it easier to get unstuck in snow? Are there some things I can do before it snows that make it easier to get out of snow?
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tl;dr: You can use a spade or similar tool in order to dig the snow out of the way. What are some methods I can employ to make it easier to get unstuck in snow? Having said that, there are several things that you can do or might want to consider if you are stuck in snow. How to Get a Car Out of Snow Check the Exhaust - Clear any snow that is covering the exhaust so as to prevent the build up of deadly gases within the interior of the car as the engine is running. They are only dangerous to people if the density of the exhaust fumes are able to rise in a confined space such as the inside of your car. Break the Ice - You can use a screwdriver, penknife, multitool or any other sharp object to be able to break the ice directly in front of the tires. The rougher surface will actually help to increase traction as you start to pull away. Remove Excess Snow - I don't know the severity of the snowfall in your geographical area, but if it is very bad you should try to remove all the snow from near the car that is above the ground clearance of the car. This might be easier said than done if your car is beached on ice, but in most situations this won't be the case. A spade or shovel would be the best thing to use for this if you are able to carry one, but if not then a garden trowel might be a smaller, cheaper and more practical alternative for you - especially if you have a small car. Another good alternative is to use a camping shovel . These are small, inexpensive shovels that serve the same basic purpose as a regular shovel in this scenario (most of them also fold down, making them even easier to stow away discretely in the back of your car somewhere). They can even be tiny, as seen in the picture below (bear in mind that the smaller the shovel, the less practical it will be). Also a good thing to have for moving dirt or soil if necessary. Chains - I know you said you didn't have chains (if you did you probably wouldn't be stuck in the first place!), but if you did then this would be a good time to put them on to give you some extra traction on the slippery snow or ice. Use a Plank - It can be very useful to be able to stick a thin sheet of metal or a plank of wood underneath each of the drive tires in order to give the car another surface to grip, rather than the broken ice that was mentioned in step 2. Floor Mats or Door Mats - If you don't have any space wood or metal that you can feasibly use (i.e. if you didn't see this post before you got stuck) then you might want to consider taking the car floor mats out of your car and using them under the drive tires instead. Do this only as a last resort as they will probably be destroyed! When doing this, be very cautious with the accelerator. Door mats can also be used, many people already have one, they are much stronger than car floor mats but will probably still get damaged to some degree or possibly destroyed. The woven door mats are cheap, and make practically ideal snow mats in an emergency. Flattened cardboard boxes work just as well, it doesn't matter if they get destroyed and they are free if you've ever bought anything off Amazon or similar. Use the Brakes - Still not going anywhere? This may sound counterintuitive, but if you really think about it, one wheel is normally spinning more than the other because it has less resistance . Pressing the brakes lightly will decrease the speed of rotation of the spinning wheel (by increasing the minimum torque that would be needed to spin each wheel due to the fact that the differential applies equal torque to each of the drive wheels in any car without any fancy traction equipment) and transfer some power to the other wheel so that both wheels are working to pull you out of the snow. Two wheels spinning slowly and working together are much better than if they were trying to work independently in this situation. Note that using the brakes extensively can lead to overheating. If this happens, just turn the engine off for a while and let the vehicle cool down. If you down and your car finds traction, be aware that your stopping distances may significantly increase until they have a chance to cool down again. Check Your Fuel Gauge - It sounds simple but you may get through a lot of fuel (especially if you have a less economical car) while you are trying to get the car out of the snow. If you know in advance that you are going to be driving in heavy snow somewhere on a long journey then you might want to think about bringing a jerry can with some spare fuel with you in case your journey takes longer than expected. Being stuck in snow does not help your MPG! Note that you should not carry fuel regularly due to its fun - and potentially very dangerous - flammable chemistry. Sprinkle Salt - The salt will help to melt ice, which tends to form when you spin the wheels (and that ice is probably the reason you're stuck). Rock salt is preferable, but table salt will also work if you use a lot of it. Sprinkle Other Stuff - Sand , dry soil (not mud!), cat litter or any other similar materials can all help to provide the car with traction underneath the drive wheels. Spare Fluids - If you have a means of obtaining hot water (melt snow on your overheated car?), extra windshield wiper fluid or antifreeze (be careful with antifreeze in residential areas, pets like to drink it off the ground and it will poison them, so don't use it where it will accumulate) in your car, that can help melt the snow/ice also. Deicer Spray - Although I disapprove of the idea of releasing these sorts of harmful chemicals in to the environment where feasibly possible, you can - as a last resort - use a chemical deicer spray in order to melt the ice. Straighten the Steering Wheel - Making sure your wheels are straight make it much easier for the car to find traction when it is stuck. Be careful to take not of any obstructions in case your car suddenly find traction. Use a High Gear - Gently accelerate until the wheels start to slip, then reverse, then forwards again until you have created enough room for you to pull out. Using a high gear such as 2nd - or even 3rd if your car will allow you to without stalling - will stop you from spinning the wheels as easily on the slippery surface. Let the Air Out - Let some air out of your tires from the valve (see picture below) stem using a pin , pen , knife , multitool , car key or similar to increase the surface area of the tire in contact with the ground at any given time, thus increasing traction. You just need something to push in the center of the valve. Use Momentum - You can rock the car using the power of the car, or the collective power of a group of selfless volunteers, or both! This momentum may help to move the vehicle out of the hole that it has inevitably dug itself in to by this point. It should be noted that using the power of the car to create this momentum by shifting quickly between gears should not be a first resort, as the transmission can become overloaded and fail when the momentum is shifted so quickly. Use the Steering (front and four wheel drive vehicles only) - If you have a front-wheel drive vehicle and the wheels are spinning, turning the wheels in a different direction can give you the extra traction that you need. Many people try to get unstuck with a very turned steering wheel as if they want to re-enter the road immediately. This can make it harder, so the idea is to turn the wheel the minimum amount possible (i.e. straighten the front wheels via steering). The front wheels being turned a small amount can resist the limited traction available to the rear wheels in slippery conditions, so straightening out the steering can sometimes help a lot. Remember to accelerate slowly or you will end up just digging yourself in again! Lift and Fill Method - If nothing else has worked thus far, the lift and fill method just might. You should have a jack in your car anyway which is all you will need to be able to do this. Clear the snow, trying to make the ground as flat as possible to make it easier to jack the car up. Put the jack on a firm base such as the plank of wood , sheet of metal or even an old hub cap should do the trick. Jack the most deeply sunk tire up as high as possible. Remember to be cautious as the jack can still easily slip in such slippery conditions. Throw anything you can find (other than snow or ice!) underneath the raised tire in order to increase traction. Use anything like a floor mat , blanket , salt , sand or even your spare tire if there is enough room for it underneath the raised one. Carefully lower the jack on to the pile of stuff. Drive cautiously out of the snow to somewhere where there is traction and don't forget to take away everything you have brought with you so as not to litter. TracGrabbers - They are a product designed specifically for use when a vehicle is stuck and can't find traction. Install one TracGrabber on each drive wheel after you get stuck. Clear any debris as much as possible that is making it harder for the vehicle to move such as snow, large chunks of ice or rocks from in front of the drive tire. Use just enough power for the TracGrabbers to be able to lift and pull the car out of wherever it got stuck. Drive slowly to stable terrain and take them off before you carry on your journey - they are not designed to be used for long distances. GoTreads - GoTreads are another commercial product you might want to consider if you live somewhere with very long, snowy winters. Work with Gravity - Many people when they are stuck in snow will try to make the vehicle progress in the direction they want to travel. If you are stuck on an incline however, you shouldn't try to fight gravity! Try to apply power to the wheels using the reverse gear if at all possible so that you are able to use gravity to your advantage, rather than fighting it. Notice here that the weight of your vehicle acts as a force vertically downwards due to gravity. The steeper the inclination, the greater the value of the force acting against you. In other words, the steeper the incline, the more effort you will have to put in to moving the vehicle up the slope. By moving down the slope in the opposite direction, you will have the same force acting with you. Gloves - Snowy environments are likely going to very cold, as such I would assume that you have already brought gloves with you when you remembered your hat , scarf , coat and hot chocolate in a flask . It is however a good idea to remember a cheap pair of thick gloves that will keep your hands warm and dry whilst you are shoveling snow in the cold. I say cheap so that if you also intend to use them for maintenance they will still allow you to avoid the yukky car goop but not break the bank if they get torn or generally ruined. You can't do anything productive if your fingers are frozen! Propane Torch - This is a fun, effective way to melt some of that rock hard ice if you had trouble using another tool due to high compressive strength. Just try not to melt a hole in your tire! You'd be surprised how easy this is to do. It is also handy for heating that hot beverage I eluded to earlier (as long as you're careful). Go Easy on the Throttle - It's a natural reaction to give the car a lot of power when you're stuck, but more often than not this decreases friction and does a worse job than using just enough to keep surface contact between tire and snow and creep out of the rut. Note that this only applies to getting out of the initial rut. If you have managed to reverse your car out of the rut, you will need to make sure you do use sufficient power to carry enough momentum to be able to drive through the place where you were originally stuck. Disable the Traction Control - By doing this, you are disabling the cars ability to restrict power to the wheels when they start to spin - thus not restricting the cars ability to gain any forward momentum should it find traction on one or more of the drive wheels. As a general rule of thumb; turn the traction control off and then allow the drive system (AWD/FWD/RWD) to handle the power distribution around the car on its own. Note that if you do disable traction control, you should watch your speedometer carefully as you may find it easy to accidentally increase wheel speed more than necessary to the point where if the car suddenly finds traction you could lose control of the car again or even cause a collision! Not to mention there probably won't be much left of your tires after that. Here and here are a few brilliant examples (though there are many others) of how Subaru cars can make progress through snow using their remarkable AWD system without traction control. Especially for Subaru cars, this can be a very effective method to use (even if the snow is really deep). What are some tools I can carry with me to help me get out of snow? Summary of Useful Things Car key - you aren't going very far without this! Spade, shovel or camping shovel Screwdriver Penknife or multitool Garden trowel Sheet of metal Plank of wood Car floor mats, door mat or flattened cardboard boxes Jerry can with spare fuel Rock or table salt Sand, dry soil, cat litter or other similar materials A pin, pen or knife A jack Hub Cap Blanket Spare Tire TracGrabbers Good pair of thick, waterproof gloves Cheap gloves Warm clothing Hot beverage Propane Torch Are there some things I can do before it snows that make it easier to get out of snow? Yes. If you do not have some or all of the things on the list above you might want to use your best judgement in order to be prepared for any situation without making your car more cluttered than your average garden shed! For many countries, snow is a rare occurrence anyway so I wouldn't suggest having all of the stuff in your car all of the time. Things to Bear in Mind Also before you leave, you can bear these things in mind: Know Your Car - Do you know where your drive wheels are? If you open your bonnet and see that your engine is mounted parallel to the front axle, you probably have a front wheel drive car. If it is mounted perpendicular, it is probably rear wheel drive. Note that some cars, such as most pickup trucks, SUVs and cars advertised as "quattro" are actually four (or all) wheel drive. This means that all your wheels are able to help pull the car out of the snow. Take your car for a short drive on the motorway - If you notice any wobble or unusual vibration then there is probably snow packed into your wheels which can cause an imbalance. To fix this, pull over when it is safe and convenient and knock the snow out of the wheels by hand (with your gloves on). Be Prepared - A motto from the scouts that certainly holds true here. Keep some of the things listed above in the boot of the car in winter months. One or more of these items can help significantly reduce the amount of time and effort needed to free a stuck car from snow and ice. Some snacks would be a wise addition to such supplies for the times that require a prolonged waiting period of time for help to arrive (not just in snow, but for breakdowns as well). Winter Tires - If you drive in an area that experiences really severe winter (as opposed to the occasional snowfall like you get once a year in England if your lucky!), consider installing snow or winter tires for the winter months. All-season tires are not nearly as effective in handling snow, mud or similar such surfaces. Be Resourceful - If you haven't got a plank of wood or sheet of metal to increase traction, go and find some sticks or pebbles nearby to use for the same purpose of increasing traction. When You Break Free - If you're moving forward when you break free, continue to drive at a steady pace, aiming for somewhere with less snow where you can safely stop, or get back on to the road. If you have broken free and are traveling in reverse, continue for a couple meters, then let go of the accelerator, allowing the snow to stop the car. Gently accelerate forward in the same tracks you just made with enough speed to break through the original spot. Don't go too slowly or you'll be back where you started! Radiator Air Flow - If you have snow packed in the front of the grille from a snowbank be sure and clear it out before you drive the car too far. It will cause overheating if the air flow is blocked. Overheating can do terrible things to the engine so this is an important one. I would love to hear any other suggestions that you may have to help everyone avoid the snow!
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25,328 |
Everyone wants their cars to use less fuel, right? I read the following passage about running the car fuel lean from this website : Run the engine fuel-lean, that is, use excess air. It is well known that fuel-lean running improves the efficiency. In the old days, under cruising conditions, the engines always ran lean – about 15% excess air -- this was economical. So what happen to change this? The problem is the three-way (CO, UHC, NOx) catalyst used on engine exhausts. This only works if the engine air/fuel ratio (by mass) is stoichiometric (chemically correct). For gasoline this ratio is 14.6:1. The engine computer, acting in concert with the engine air flow sensor, electronic fuel injectors, and exhaust oxygen sensor, maintains the stoichiometric ratio for most of your driving. Only at this ratio can the catalyst both oxidize the CO and UHC (to CO2 and H2O) and chemically reduce the NOx (to N2). (UHC = unburned hydrocarbons.) What humankind needs is a lean-NOx catalyst. Then we could have increased efficiency and continue to be clean! This passage seems to make total sense. Use more air and increase fuel efficiency. However, I don't understand why the catalytic converter can't handle or be adapted to handle more air in the engine. What are the advantages and disadvantages to forcing air in to the engine by means of a turbo or supercharger that would justify a car doing or not doing it?
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Lean ≠ More Air I believe the source of the misunderstanding is in how the term "lean" is being interpreted. A lean mixture doesn't indicate the presence of more air. It indicates the presence of a higher proportion of air compared to fuel (air-fuel ratio, or AFR ). Quick example Mixture A has 1,000 g of air, 80 g of fuel. AFR = 1000/80 = 12.5 Mixture B has 100 g of air, 7 g of fuel. AFR = 100/7 = 14.3 Since 14.3 > 12.5, Mixture B is leaner than Mixture A, even though Mixture A has more air. This is why @cdunn is right ; the presence of a turbocharger or supercharger doesn't impact the ability of an appropriately-sized catalytic converter from doing its job. So why is it not good for cats to run lean? A catalytic converter is designed to scrub harmful gases out of exhaust gases. It does this through a chemical reaction that involves the presence of catalyst(s). The most popular type of cat design today is the three-way catalytic converter, which handles three types of harmful gases: nitrogen oxides (NOx, not NOS) carbon monoxide (CO) unburnt hydrocarbons (HC) The catch is that cats work well in a narrow AFR window, as this image shows: Run too lean , and the cat will have a hard time scrubbing NOx out of the exhaust gases Run too rich , and your tailpipe will have a lot more HC, CO content
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25,561 |
What is CAN (controller area network)? What are the differences between an OBD-II protocol and a CAN setup?` How do I use an OBD-II scanner on a vehicle with CAN?
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Ok, before I will answer your specific questions, let's do some introduction on bus systems. It could be that you know parts of these things, but I will start here as people with little or no IT or electronics knowledge should be able to understand this as well. Bus Systems In electronic systems signals are sent from one chip to another using wires (let's forget about wireless things for a second). The simplest way of doing so is to use one wire per bit of information you like to transmit. One bit of information is simply an answer to a yes/no question like "Are the headlights on?" If the headlights are on, there is a voltage on that wire, say 5 volts. If they are off there are 0 volts on the wire. Now that's fine for one bit of information. But more data requires more wires. Unfortunately: More wires means more complexity. A modern car is just a computer with tires on it , so there are a lot of wires ( serveral km or miles ) in it. More wires result in more weight and more costs and car manufacturers don't like that. So we need a way to reduce the amount of wires. The usual way of doing so is to use a bus system . What is a bus system? Think of a bus as a way to transmit more information using fewer wires . There are other benefits of bus systems, but I will focus on this aspect. Example: We want to switch four lamps on or off. Without bus system: Lamp 1: +5 V on Wire1 = Lamp is on; 0 V on Wire1 = Lamp is off Lamp 2: +5 V on Wire2 = Lamp is on; 0 V on Wire2 = Lamp is off Lamp 3: ... Lamp 4: ... It's easy to see; we need one wire per lamp. With a bus system: Lamp 1: +1 V on Wire1 (Selector), 0 or +5 V on Wire2 for on and off (switch) Lamp 2: +2 V on Wire1 (Selector), 0 or +5 V on Wire2 for on and off (switch) Lamp 3: +3 V on Wire1 (Selector), 0 or +5 V on Wire2 for on and off (switch) Lamp 4: +4 V on Wire1 (Selector), 0 or +5 V on Wire2 for on and off (switch) With this primitive kind of bus system we reduced the amount of wires to two . Regardless of the number of lamps we like to control, we only need one wire to tell the other chip which lamp we like to switch and a second wire to tell it wether we like to have the lamp on or off. My example would have limits in the real world as one can't simply raise the voltage to 1000 V on Wire 1 to switch a thousand different lamps. This example shows, why in electronics in general and in cars in particular bus systems are being used. Cars use a number of bus systems that were made especially for them: CAN LIN MOST FlexRay K-Line What is CAN (controller area network)? CAN is the most important bus system in a car. I won't go into detail on this point, just think of it as a way to transfer big amounts of data using only two wires. You can read more about CAN on Wikipedia . OBD-II What are the difference between an OBD-II protocol and a CAN setup? OBD-II is a higher-level protocol used for diagnostic purposes. OBD-II can use one of (many) different bus systems to transfer diagnostic data from and to your car. Think of OBD-II as a language (English) that you speak and of CAN as the communication device (telephone) you use to talk to someone (about your car and its state of health ;). Many people are referring to OBD (short for on-board diagnosis) or OBD-II as "standards". OBD-II is a standard, but it again consists of so many different standards, protocols and bus systems used to communicate that it's difficult to list all of them. I once made an overview graphic, and I will see if I can add that to my answer later. How to use OBD-II scanner on a vehicle with CAN? Just plug it into the OBD-II port of your car. CAN is one of the transport protocols of the OBD-II specification and should be supported by most OBD-II-Scanners The location of the port can be found using a Google (image) search. Usually the port is located in reach of the driver , e.g. under the dashboard or hidden in the center console .
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25,626 |
When one wants to park a manual transmission (MTX) vehicle, one puts it in neutral, and engages the emergency / parking brake. With an ATX vehicle, the practice I've learned is to put it in Park, and engage the parking brake. But if I need to engage the parking brake, then what exactly is the purpose of selecting Park? What does selecting Park do and how does it differ from selecting neutral?
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In an automatic transmission there is a ring with teeth on the output shaft of the transmission. When the transmission is shifted into park a lever called the parking pawl is lowered against the ring. If the parking pawl did not land squarely into an opening in the ring the car will roll slightly and there will be a usually an audible click. The parking pawl now holds the output shaft from turning. Without the engine running an automatic transmission is effectively in neutral in any gear except park. Theoretically with park engaged also applying the parking brake is not necessary unless the car is on a big hill because the parking pawl has more than enough strength to hold the car from rolling. It is a good idea to exercise the parking brake on a car with an automatic so the system does not freeze up. PS. In a manual it is suggested to place the car in first gear or reverse then engage the parking brake and for good measure curb the wheels. In the event that the parking brake fails (more common than the parking paw) the engine with the sub one gear ratio will hold the car. The good measure of curbing the wheels will roll the car into the curb in the case that the engine can't hold the car from rolling.
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26,565 |
I have a 1998 Honda Accord. I am driving today and I know that I need new brakes. They make a metal on metal screeching sound when I brake. Today as I go to brake at an intersection I hear a loud pop and my brakes stop working. I was able to avoid an accident and pulled over. I try driving on the small streets slowing trying my brakes. They seem to be stopping slowly and loudly. I know I can't put off getting new brakes but not sure exactly what I need to replace. I'm thinking at least the front pads, front rotors, maybe driver side calipers, and maybe the brake line. Anyone have any ideas as to what happened? I need to replace and how much longer can I drive like this? Any input is good. If you need more information, let me know. Thanks. UPDATE! Had it towed to a mechanic shop. Forgot I had roadside assistance from my car insurance, wasn't worth driving like that. Mechanic says I need all 4 rotors, pads, and calipers. That all the brakes are locked (not sure what that means). Cost to replace: front rotors and ceramic pads = $240, rear rotors and ceramic pads = $240, and all 4 calipers, 4 x $150 = $600. For a total of $1080. He said he would throw in replacing my catalytic converter for free (i knew i had to replace it before).
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Yes. One of your brake pads on the caliper side of the brakes had been worn so far down it popped out of place. Now you are stopping using the caliper piston against the brake rotor. You will now have to not only get the brake pads and rotors replaced, but the caliper as well. If you cannot fix this yourself, you should get the vehicle towed to a repair shop. DO NOT DRIVE it any more until you do. As others have said, you are risking not only your own life and property, but everyone else's around you as well.
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|
26,886 |
I do realize that it stands for revolutions per minute, but what are the revolving pieces that are measured? Assuming it is the crankshaft, is RPM calculated by the crank shaft sensor, or by some other means? Why do some old, carbureted cars not have a tachometer--is it for the lack of the ECU and the sensor? Here's a scenario: A 1,000cc 4-stroke engine with 4 cylinders is running at 1k RPM. How many times does each cylinder fire per second? How can this be calculated? Also, does the piston provide force to the crank shaft with each stroke, even during the exhaust stroke? Does the engine create equal torque with each stroke of the piston, or do each of the four strokes apply different amounts of power? If so, why don't the RPMs fluctuate with each different stroke of a cylinder?
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Ok, let's start from the same picture so we're on the same page: These engines are four stroke engines, which means the piston goes up and down a total of 4 times, twice up, and twice down for each cycle. So to answer your questions: Of course I do realize it stands for revolutions per minute, but revolutions of what? As you stated later, it's revolutions of the crank shaft. I assume the crank shaft, how is it calculated, is it by the crank shaft sensor? Why do some old cars that runs with a carburetor don't have the RPM meter is it for the lack of the ECU and the sensor? As for how it's measured, there are both mechanical and electrical ways to measure it. Older cars didn't have a tachometer just because they were not popular, and to limit the cost. Many older cars did have tachometers though, just mechanically driven. I'm not 100% sure where the pickoff was for this, but if I had to bet it was just a gear off the crankshaft that gets reduced to a needle movement on the dash. In the same way that the speedometer was usually a gear in the transmission that did the same thing just for wheel speed. As for the electrical methods, yes, it's just a sensor talking to the ECU which sends the right PWM (Pulse Width Modulation) signal to a gauge in the dash. Also assuming a 1000 cc big 4 stroke engine with 4 cylinders running at 1k RPM how many times are each cylinder firing per second or how can that be calculated, also does the piston "revolve" the crank shaft with each stroke even at the exhaust stroke with the same torque or is it different at the firing stroke, if so how is the RPM not constantly going up and down with each different stroke To lay this out, lets look at how many times the shaft rotates with each stroke. From the diagram you can see that a full up and down path of the piston makes for one revolution of the crankshaft. That means in a four stroke engine the shaft rotates twice (two revolutions) for every four stroke cycle, which means one power stoke for every two revolutions of the crank. So, if the crank is turning 1000 times per minute, that would be 500 power strokes (firing of the spark plug) on each cylinder in that one minute. Since there are 4 cylinders, there would be 2000 sparks in that one minute across the whole engine. And no, the piston does not produce the same torque on every stroke. In fact it only produces torque on the power stroke. The other three it's just along for the ride. As for why RPM does not vary constantly, the plugs don't all fire at once. The power strokes are spread out so that during the rotation of the crank the power is divided amongst the 4 cylinders so one of them is almost always producing power and turning the crank. In addition, the flywheel has a lot of mass, and tends to smooth out the roughness of each individual cylinder firing during it's power stroke. Otherwise it would be a much rougher cycle. I think that covers it all, if anyone finds something I missed, or if I managed to get something wrong, please yell and I'll just edit it so we have this right. I hope that helps!
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|
26,936 |
Some people say they wash the outside car every week as it makes the paint nice etc Are there any benefits of washing the outside of my car? Do I really need to wash the exterior of my car every week? Does it damage my car if I don't wash it for a month or two? I would like a general answer, but the specific car is a 2003 Opel Agila Obviously I clean the interior ;)
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tl;dr: How much did you pay for that shirt? How often do you wash it? Why would you bother? Shirts just get dirty anyway. Can't you get another shirt? Are there any benefits of washing the outside of my car? Do you live in an area without salt, birds, tree sap, pollution, abrasive sand or road tar? Do you also drive around with brake pads that don't emit corrosive dust? If so, then you might be okay to avoid washing. If not, then yes, there are plenty of benefits. Do I really need to wash the exterior of my car every week? Does it damage my car if I don't wash it for a month or two? What's practical for your situation? If you can't wash the car for a while because of life circumstances, the point is moot. Here in the Northeast USA, car washing is actually seriously important. For example, salt is a year-round fact of life here in Rhode Island. In the winter, it's used to treat the roads during snowy weather. In the summer, it's fun to go to the coast (admittedly, Rhode Island is basically all coast but still...) where the wind is picking up all that salt spray and misting it all over the car. Even better, seagulls drop blobs of acidic smears of grossness all over that deliciously salted car. Some people will try to argue that clearcoat and paint will protect the metal of the car. While that is technically true for a while, neither is sorcery. Any sort of corrosive or abrasive will eventually wear through that protection and start rusting. As a practical example, that gravel shot into the hood of your car by the truck in front of you may have chipped the hood down to the metal. It almost certainly took off the clear coat and a layer of paint. Any sort of washing will get all that nastiness away from the car with the side benefit of making it look nicer. And remember, anything is better than nothing: I spray out the underside of my car while I'm washing it. I'm not using special undercarriage spray or anything like that, just a straight up garden hose. The startling amount of sand and salt that pours out from under the car could be used to make little castles in my driveway. It's also a convenient time to just walk around the vehicle and check for any issues. Is that piece of trim coming loose? How long has that screw been missing? Here's a rock chip: I better get some touch-up paint into that right away. All of the above is bounded by reality. In the winters here, sometimes it's just too cold to wash the car for months at a time. Some of those times, washing the car is effectively moot anyway since all that dirt is getting hidden under layers of snow.... Pro tip : a clean car is much more pleasant to work on. Even if you don't handle your own maintenance, the techs who do will be grateful that they aren't working in a gross muddy rust pit.
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|
27,361 |
I was wondering what the specific mechanism used by car ECU's to detect misfires is, or are if there is more than one method.
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This comes directly from this web site: http://www.obdii.com/articles/Onboard_Diagnostics_Demystified.html What it says, is that early OBD-II systems could not detect misfires, but since then a few variations on the theme have been implemented. The basic idea is that if a cylinder fires, it gives a kick to the crankshaft causing a slight variation in crank shaft rotation speed. The ECU has sensors that tell it the position of the crank shaft, from which it knows which cylinder should be firing next. When an ignition happens as it should, that's the power stoke and it gives a little kick to the crankshaft causing a slight increase in the RPM. The ECU sensors can tell it the crank position closely enough that it detects that slight increase. If the slight increase doesn't happen, the ECU knows that there was no ignition on that cylinder. Which is also how it knows which cylinder didn't fire, and how it reports which one it was through the code it throws.
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|
27,889 |
Imagine we're going down a hill and we're driving a manual car. There are two situations: If I put my car in neutral it will go downhill without any need for the injector to squirt fuel into the system, just enough fuel for the engine to idle. I put the car in the last gear (5th on my car) and let the gravity pull my car. Which situation will consume less fuel? Edit: Both the title and the last sentence, which I have highlighted, clearly state that I am asking about fuel consumption.
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If the car is equipped with a modern fuel injection system, it will likely use less if left in gear and allowed to run against the transmission with no throttle as modern fuel injection systems can and do shut down the injectors completely thus use no fuel whatsoever. If the engine is at idle in neutral, the ECU will have to use a small amount of fuel to keep the engine turning.
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|
28,188 |
Every year in Arizona there are monsoon storms and somebody inevitably get's killed in a car that is sinking in water. It appears the primary issue is getting free from the vehicle. After that, there's an entire set of other issues. Aside from that, how can I free myself from a sinking vehicle? Is there anything I can do that's pro-active in case it happens? What are the problems that need to be solved quickly in order to be successful in extricating myself from a car that is stuck in water and rapidly sinking?
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If you can open the door, do it Then unbuckle, and bail out. If your car has sunroof and it works, open it and exit from it Your car electrics need to be functioning for this to work though. On some cars like VW's you can pop off an inner roof panel to reveal a hand crank to open the sunroof. Detach the headrest, use it to shatter the window glass¹ If you can't roll down the windows Take headrest off the back of the seat Push one of the pegs from the headrest attachment in between the window and door card, just where the seal is. Jam it down in there a few inches Pull the headrest towards you to shatter the glass Clear away shattered glass remnants and exit from window Here is a video demonstrating how to shatter the glass. This is one very good reason for manufacturers to keep car seat headrests detachable. The key here is to wedge the peg into the gap between the door card and the window and use a lever action to shatter the glass. Hitting it isn't as reliable. Hope this helps someone. Maybe even save a life.
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|
28,385 |
So it's time to raise the car onto jack stands, but for whatever reason it needs to go higher than the stand height allows. How can I safely raise the height of the car? What I have done in the past is put a 2in concrete pave stone under the stand. It's much bigger than the base of the stand, and is flat against the ground and the top surface is flat for the stand to sit on. Is that too much weight for the stand? i would hate for it to crack and drop the stand to the ground with me under the car. What is the safe way to do this? I mean besides buying a lift.. :)
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You could always look into jack stands that are typically used for heavy duty trucks and semis. One time I had a lifted truck I had to go to Northern Tool and purchase high reaction jack stands: Item link That said I wouldn't recommend using anything other than the jack stand. Even if you are using a block that block could still break from the pressure being applied and you would be crushed. Safety should always be top priority. You just need bigger stands.
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|
28,503 |
We have a lot of stray cats in my neighborhood and they possess an uncanny ability to know when a car has been cleaned for them to sit on and enjoy. Needless to say, the dirty, dusty paw marks they leave behind is a hassle to clean. The ideal solution would be to use a car cover, but to use it on a daily driver is highly impractical. Are there any proven cat-repellent products that are specifically designed for cars? The last thing I want to do is apply some generic household product and damage the paintwork. A quick Google search reveals that some products and techniques do exist, but they are either impractical, provide limited protection or difficult to get hold of. I'm open to humane suggestions. No ethylene glycol. No spiked tuna, etc.
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Place a cardboard box next to your car. If science has told us anything, it is "if they fits, then they sits".
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28,561 |
This previous question explains what a flywheel does and why it is needed. That explanation means that the flywheel needs a certain amount of mass to do its job. However, an "upgrade" for many cars (when looking at performance enhancements) is a "lightweight" flywheel. Removing weight from a performance car is a normal thing to do, so a lightweight flywheel seems like a good choice, but doesn't it need that mass? What are the advantages other than sheer weight loss to the upgraded flywheel? If it was only a good thing than the OEM flywheel would be lightweight already, so what are the cons? Is there such a thing as a heavyweight flywheel? Ultralight Flywheel for Honda Civic
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The main advantage to a lower flywheel mass on race cars is that the reduced mass allows the engine to rev more freely. The overall weight loss to the car is really not the key thing, it's letting the engine vary RPM really quickly. Being able to change RPM quickly can mean faster shifts, getting to a power band more quickly, etc, etc. It also makes the car much more twitchy to drive since it doesn't like low RPM very much. At low RPM the lower mass of the flywheel means you need to use the throttle to keep the RPM above where the flywheel isn't going to carry things around as well. For a race car that's not a big deal. For the family driver with the manual transmission, it's a big problem.
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28,775 |
Since fuel is made up of different molecule chains, my question is what is the reason we cannot create the same molecule structure and be able to reproduce the same structure in a lab so we don't have to run out? I understand there's way more to this and it's not as simple as I make it seem but that's why I am asking: what are the challenges in doing something like this? Can we not make the same structure? Also as a side note, do fuels have oxygen molecules already inside the chain or do they not receive these molecules until the mixing of the oxygen using valves?
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Oil as it comes out of the ground is a mixture of hydrocarbon compounds that are the remains of deposits of algae and microscopic animals, also called phytoplankton and zooplankton. Scientists have already created synthetic fossil fuels. The efforts 1 . There is currently a $300 million dollar (actually much larger) effort in San Diego, California by a company called Synthetic Genomics and Exxon Mobil to use algae to make oil. The lipids, a form of fat, in the algae are a major component of crude oil. Excerpt from: http://www.sandiegouniontribune.com/news/2009/jul/15/1n15algae001356-deal-blooms-algae-biofuel-research/?uniontrib A San Diego biotechnology company led by genomics pioneer J. Craig
Venter has landed a deal with Exxon Mobil that could include more than
$300 million in funding to develop biofuels from algae. Venter, best known for his role in sequencing the human genome, said
yesterday that his company Synthetic Genomics is planning a local
greenhouse and test facility to study thousands of strains of algae
from around the globe. The eventual aim is to engineer algae that would use energy from the
sun to convert carbon dioxide into oils and hydrocarbons in large
quantities – a feat that would be prohibitively expensive with
naturally occurring algae. As of now the above project has failed and is back to the drawing board. Excerpt from: https://www.technologyreview.com/s/515041/exxon-takes-algae-fuel-back-to-the-drawing-board/ Those efforts don’t seem to have cracked the code for cheap algae
fuels. In a new agreement between the companies, Exxon is sending
Synthetic Genomics back to the lab to do more basic science. It will
focus now on its namesake technology–synthetic genomics, a relatively
new science that involves making large changes to genomes, even to the
point of building whole new ones. The goal remains the same: “to
develop strains which reproduce quickly, produce a high proportion of
lipids and effectively withstand environmental and operational
conditions.” 2 . Chevron has a joint effort with a company called Catchlight Energy to use algae as a raw material for making petroleum. Chevron has also partnered with Weyerhaueser Co, one of the worlds largest forest-products companies to begin using wood waste. Ligno-cellulose found in wood is also a component of petroleum. Excerpt from: http://investor.chevron.com/phoenix.zhtml?c=130102&p=irol-newsArticle&ID=984280&highlight= Chevron Corporation (NYSE: CVX) and Weyerhaeuser Company (NYSE: WY)
today announced a letter of intent (LOI) to jointly assess the
feasibility of commercializing the production of biofuels from
cellulose-based sources. The companies will focus on researching and developing technology that
can transform wood fiber and other nonfood sources of cellulose into
economical, clean-burning biofuels for cars and trucks. Feedstock
options include a wide range of materials from Weyerhaeuser's existing
forest and mill system and cellulosic crops planted on Weyerhaeuser's
managed forest plantations. In nature, the only reason it takes millions of years for these organic materials to change to oil and natural gas is that it takes that long for it to be buried to a depth where the temperature and pressure are high enough to convert these materials to petroleum. In reality, the time it takes to convert these from algae to oil may be less than a few hundred years, and that again is because of the slow change in temperature and pressure in a geologic setting. Oil has been generated and found in sedimentary deposits as young as 1000 years old, so it does not require millions of years. In an industrial setting this all can be done in a matter of hours or days. Challenge In the lab, organic material can be heated (~320C) up in an inert atmosphere with water under pressure (~150 atm) to simulate the natural processes that take millions of years but take only a matter of days in the lab. This is due to simple thermodynamics, thousands of years at 100 C or a few days at 320C give similar products. This technique is used to analyse whether immature rocks, if they had been buried more deeply, could produce crude oil. So it can be used as a tool to search for oil reservoirs. It is not economically viable to do it on a large scale since so much energy has to be put into the system. Side thing As for this point, The chemical composition of gasoline does have oxygen in it such as ethanol blended gasoline or methanol blended gasoline but it can't behave as oxygen. So it needs oxygen from outside, namely air. When these two components are ignited it combusts and releases energy. Basic chemistry. Here is the reaction happening inside a cylinder during the combustion stroke. 2C 8 H 18 + 25O 2 → 16CO 2 + 18H 2 O Hope this helps!
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28,916 |
Are classic cars safe? I am interested to know the differences between modern vehicles and vehicles of old from the 1960s. In the event of an accident, how does a classic vehicle compare to a modern machine? Are safety features on new vehicles really a life saver? Can anything be done to improve the safety of classic vehicles? Are classics safe enough to be used as a daily driver?
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Physical safety Modern cars are amazingly more safe than classic cars. Guys that are into classic cars frequently throw around phrases like "They don't make them like they used to!" or "This is built like a tank with real American Steel!", but when you look at a classic car in an accident, the results are pretty obvious. In 2009 this crash test was done between a 1959 Chevy Bel Air and a 2009 Chevy Malibu . Click for video Source: http://www.iihs.org/iihs/sr/statusreport/article/44/9/2 The aftermath of the crash shows how the modern "crumple zones" almost completely protect the driver's area in the 2009 whereas the 1959 driver would certainly be badly crushed. In addition to crumple zones built into the frame, there are other thoughtful features like collapsible steering columns and as a high tech option the car will call and report the accident to emergency responders for you. From the comments (thanks tallpaul): here is another video of a 1980 Volvo and a 2000 Renault. Not classic per se but it does show a marked difference in technology even in that 20 year span. Anti-lock Braking Systems Modern cars also come with ABS which reduces stopping distances while maintaining a level of steering control. The difference between the car sliding to an uncontrolled stop and quickly slowing down while being able to steer around obstacles or even to just stay on the road is huge. Restraint Systems Cars from the 60s and earlier don't even have a 3-point seatbelt (shoulder belts), but modern cars are required to have them, and many also have seatbelt tensioning systems that tighten the belt and hold you in the seat in an emergency. In addition to better belts modern cars also have several airbags to cushion the occupants in an accident.
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29,139 |
I have a 2001 Chevy Malibu and have replaced the engine coolant in it twice in the last six months after the low coolant warning light came on, and the light has recently come on again. The climate is mild here so there's no risk of freezing, and I do keep an eye on the temperature gauge - it doesn't seem to go very far above 180 degrees F in steady-state, which is about 10 degrees above where it sits with full coolant. Is it safe to continue driving with low coolant as long as I continue to watch the temperature gauge? If not, what are the potential risks involved? Update: About a week or so after my original post, I decided to refill the coolant reservoir yet again and hope for the best. Not 48 hours later, I was on my way up a hill and suddenly the temperature gauge spiked up to the red line. I immediately stopped driving and had my car towed to the nearest repair shop. Turns out the intake manifold gasket had failed which was causing the leak. Fortunately there was no damage to the engine, but unfortunately the manifold is apparently very inaccessible in the 2001 Malibu, requiring more time to replace it. $1600 and 24 hours later (which included a coolant flush and two oil changes, the first of which was to clear out coolant contamination), my car was running fine.
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"Is it safe to continue driving with low coolant as long as I continue to watch the temperature gauge? " No, the temp sensor reads coolant temperature, if the coolant gets low enough to be below the temp sensor, now the sensor is reading metal temperature of the area it is screwed into (usually cylinder head), by the time it reads too hot on the gauge the motor is toast. I have made lots of money off of people doing this.
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29,595 |
I've been having a few problems that might be electrical in my car. Seeing as mechanics always want to replace parts first, I'm having to diagnose this problem myself. It seems like replacing all the fuses would be cheap and preventative, and more effective than a voltmeter with my limited knowledge of electrical. I drive a 2004 1.7L Honda Civic Si, the US version. Could this cause problems for my car? Would it help with the diagnosis?
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Fuses do not need to be replaced unless they have blown, so it's not a regular maintenance thing. In terms of checking them, depending on your vehicle, many only require a visual check to see if the metal is present or missing. If you do have fuses where their status is not obvious, a good multimeter is only a few dollars (probably cheaper than replacing all the fuses, anyway) - and you will find it useful round the house, and for other small jobs once you have one. Make sure you get a reputable brand. Replacing all the fuses should not cause any problems with your car, unless you get the fuses wrong, or don't fully seat them etc. On balance, much better off just testing them all with a meter.
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30,299 |
Back in 2014 someone broke the right side window of my VW Golf. I was in a hurry and short on cash so I "temporarily" cut a 4 or 5mm thick piece of plexiglass ($8), bent it with hot air and placed it in my car thinking that a few weeks later when it will be worn out I would replace it with a proper window. It's been closing in two years and it is still crystal clear (which is why I kinda forgot about it), though with microscratches if you look really close. Still transparent as ever. I'm bringing this up because yesterday two guys on a bike attempted to steal my briefcase. Stopped right next to me on a red light and one of them tried to smash through the glass with a hammer. The tool bounced right off the window and hit the driver of the bike on the helmet. They almost fell and fled ungracefully. For a very long time I thought that plexiglass is not fit for automotive purposes but now I am reconsidering. Apart from the windshield (which would degrade faster due to direct impact of microparticles), what do you think are the reasons that plexiglass is not considered for car windows?
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Plexiglass is flammable. While it doesn't release toxic gases or excessive amounts of smoke, it is still rated B2 (normally flammable) and thus forbidden as interior material in motor vehicles, including windows. Here is a relevant US standard if you're interested in details. Collision behaviour mentioned by Thomas is also a crucial property, especially for bigger pieces like windows. If that guy on a bike had a bigger hammer, he could have popped your window inside the vehicle, where its shards would have released their kinetic energy by hurting the driver and the passengers. The same thing could have happened on a side collision with another car.
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30,450 |
My father (an engineer, but not an auto mechanic) taught me to use a tiny dab of machine grease on the thread (not the rim) of each wheel bolt. This would help against corrosion, and help when loosening the bolt. We've traditionally always switched summer/winter wheels ourselves, on the premise of time and money saved for a simple operation. (Yes, we do use a torque wrench and check the bolts after 100km.) Online and offline, there seems to be a great deal of argument whether or not to lubricate wheel bolt threads... has this site been able to find a canonical answer? I searched through the tagged questions but didn't find it even mentioned. If I want to make an informed decision myself, what sorts of pro or contra arguments should I consider?
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Do exactly what the manufacturer of the vehicle states in service information. Why do I say this? The nut rotational friction and bolt clamping force are both affected by the choice of lubricant used or lack thereof. Almost all OEM's specify no lube. This is done for several reasons. Dry results in the most thread rotational friction, a most desirable attribute, this significantly reduces the chances of the lugs backing off and the wheel coming off. The biggest concern is a wheel coming off at high speed. This is a highly dangerous event because the wheel accelerates ahead of the vehicle as it comes off at great speed and can and has caused deaths. Of slightly less importance, but still relevant, is that lubricated threads create a higher clamping force for a given torque than specified. This can stretch the studs or bolts, warp the hub flange and/or brake rotor. I am an Mechanical Engineer and work in the vehicle repair industry. This topic has been a topic of some debate on professional industry forums. Much to the concern of the informed on said forums is that a significant portion of professional technicians refuse to heed the OEM specifications for both lubricants and torque specifications.
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31,797 |
I was thinking today, what is the actual point of an exhaust? Why can't we just have a pipe going out the front of a car instead of taking all the gases to the back of the car? I can only see disadvantages of the current design: The expense of manufacturing a long metal pipe, which has to be the length of the car. It would be a lot cheaper to make it come out at the front or the side More to repair. Loads of old cars have leaking exhausts, and are always a nightmare to find and are expensive to fix. It would be easier to move the exhaust to the side or front and shorten it Added weight means more fuel consumption Repairing damage from going over speed humps at speed, loads of them round here have scrapes from exhausts on. As everyone always asks what things are, here is a speed hump (shamelessly stolen from Wikipedia): What are the points of exhausts? Why can't we just let the gases out into the engine compartment, or out the front or side of the engine? If we can't let them into the engine compartment, why can't we just let it out at the side of the car, instead of at the back?
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Safety, comfort, noise and space are the things that come to mind. Safety Exhaust gasses are hot as hell. Hot enough that we put heat shields all over the exhaust line. In engines, we are actively trying to remove heat. Adding more from the exhaust goes completely against that and would increase overheating. Also, would you want a hot exhaust pipe near your door, nicely exposed for you to brush a leg against when getting out? I don't. Comfort If the exhaust came out the front or the side, you would be far more likely to breathe in your own exhaust, either through an open window or the ventilation system. No thanks. Noise We need to put a muffler somewhere. The space near the engine is already being used pretty heavily. So you would either have to design something smaller or live without one. Since there are laws some places regarding having a muffler and creating excess noise, car manufacturers are going to put them on there so they can sell cars. Space As alluded to above, there are large components (muffler, catalytic converter) that need to go somewhere. And they don't fit up by the engine.
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|
32,020 |
So today was that epic event of walking out into the parking lot at high noon, sun blazing, and finding out you have a completely flat tire. Skipping over the usual details about changing out a tire with insufficient equipment on scorching hot pavement, I changed out the tire for the spare and dropped the flat tire off at a tire shop for repair. When I got my vehicle home and was putting away the spare, I noticed that the nail was still in the tire itself. The nail appeared to be a roofing nail based upon the size of the head. There also appeared to be some sort of sealant surrounding the nail. My question is if it's normal to leave the nail in the tire or not. With previous leaks, other repair shops have removed the nail or screw. I haven't been to this tire shop before so I don't know if what they did was standard practice or not.
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Nope, not normal You do not leave a foreign object in a tire under any circumstances. The object can dislodge itself during higher speeds and lead to deflation creating a very high risk event. If they plugged the tire there will be a rubber plug with vulcanizing glue but not a nail or other related object. Validate that it's not a rubber plug, if it's not, go back to the shop. This is not normal in my experience and IMO very dangerous.
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|
32,479 |
An answer to a question asking about torque wrench maintenance mentions to not use a particular kind of torque wrench for loosening bolts. This got me thinking. I would think it'd be preferable to loosen the bolt first, then use the torque wrench to re-tighten the bolt. Why would someone want to use a torque wrench specifically to loosen a bolt?
|
Sometimes you want to measure breakaway torque. This can tell you if a fastener has started to loosen due to vibration, or was over-torqued and the bolt/stud may have stretched or weakened, or the fastener was cross-threaded and need to be replaced. Note that breakaway torque values will often be higher than the stated torque spec, as the breakaway torque measures static torque (the fastener is not moving), while the tightening torque is a dynamic value (because the fastener is still moving).
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|
32,763 |
I have always changed the oil in my vehicles with the engine hot, because the manuals always say to let the engine reach normal operating temperature first. Oil change instructions all over the internet say this, too. I've never done it cold because everything says not to, and I never questioned this. I've burned myself on more than one occasion, last night being the most recent, and it makes it trickier to get the filter out when you have to play Operation on a hot car. Why do I have to change the oil when the engine is hot and what happens if I do it cold?
|
The benefits of changing it hot are the that oil is less viscous, so it flows better, allowing more of the old oil to drain. It will also drain more quickly. I know when I do mine, I let the engine warm up, but not to full operating temperature. Even through latex gloves, full temp oil would burn my hand, and I can do without that. And getting it at least more than warm but not scalding hot, things flow really well. This way you get the best of both worlds, including not burning yourself. Hope that helps!
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|
33,043 |
Why don't rally cars have airbags? Other competition cars, including Ken Block's don't have airbags either. Is it just for weight reduction, are they redundant or is there another (major) reason?
|
For the most part, they don't need it. The purpose of the air bag is to protect the occupant as the body is thrown forward in a crash. Most racers have such vastly improved safety equipment over what is available in a standard road worthy automobile, they don't need air bags. The things you'd need to take into account are things like a five-point harness, which pretty much holds the driver in the seat and does not allow him to shift forward, even in a crash. A standard automobile has a 3-point harness, which keeps the body in place for the most part, but is no where as efficient as a 5-point is. Most racers also use what's called a HANS Device . This keeps the head in place during a crash, alleviating any strain on the neck during a high speed incident. These two pieces of equipment make airbags pretty much useless in a race car. With these safety items in place, the body doesn't go forward, but rather is kept in the seat and is better protected.
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|
33,678 |
This is probably ridiculous question but I can't seem to find a chart on google that explains typical parts of a classic american car. I always seen that round disc like cylinder on top of many muscle car engine . what is that called? PS - I am no mechanic just curious. thanks
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You're talking about a classic air filter housing. Older style air filters were round in shape and sat inside a round metal enclosure. This is a Holden straight 6 from the 80s, where the air filter element is housed and sits on top of the carbeuretor. It's interesting to note that even modern cars, the check engine light still has a silhouette of an classic shape engine with the air filter sitting on top.
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|
33,776 |
I have an old Toyota in which the handbrake wire is broken. I have been using the car for few months now and I don't really want to spend more money on it. I now put the car in park and that is it and I had an argument with a friend on this matter. My questions are: do I really have to replace this wire knowing that I use the car to commute and short trips? could this affect the brakes of the car and cause it to fail faster than it is supposed to? is there a better practice?
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No, its up to you No No Assuming it is an automatic transmission using park is safe, there is a park pawl in the transmission that mechanically locks the output shaft, actually better than a parking brake. The slight roll forward (or backward depending on incline direction) is normal for an automatic park pawl, the movement of the car rotates the output shaft slightly to engage the pawl. Only downside is if you are on a steep grade it might require some effort to take it out of park due to the load on the pawl, but does not hurt anything to do so. generic image of park pawl
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34,941 |
I always run oil around the rubber rim of the new filter, and screw it in by hand, maybe a couple of twists with an oil filter strap wrench. But when it comes to removing it, it's a massive ordeal. It just wont budge. I've broken strap wrenches and claw sockets. Most times, I end up having to drive a thick screw driver through the filter, adding a breaker bar to it, and hammering or levering the damn thing. Is there something weird going on here? Is there a trick to making it easier to come off for next time?
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... and screw it in by hand, maybe a couple of twists with an oil filter strap wrench. Don't over-tighten it. Tighten it by hand then at most about a quarter turn with a strap wrench or by hand (definitely not a couple twists!) A good indicator is if you can unscrew your new filter by hand with just a minimal amount of initial strength. Go for this when installing a new filter. If the new filter you just installed requires a wrench or some serious muscle to unscrew, you've got it on too tight. If you want a number for it, my vehicle calls for 16 ft-lb torque on the filter, others are similar. Fwiw, I've only ever hand tightened them.
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|
34,945 |
When the engine is hot the starter it will not work. When I run a wire from the battery to the neutral safety switch it starts. Also, after it cools down it starts.
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... and screw it in by hand, maybe a couple of twists with an oil filter strap wrench. Don't over-tighten it. Tighten it by hand then at most about a quarter turn with a strap wrench or by hand (definitely not a couple twists!) A good indicator is if you can unscrew your new filter by hand with just a minimal amount of initial strength. Go for this when installing a new filter. If the new filter you just installed requires a wrench or some serious muscle to unscrew, you've got it on too tight. If you want a number for it, my vehicle calls for 16 ft-lb torque on the filter, others are similar. Fwiw, I've only ever hand tightened them.
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35,659 |
I'm finishing studying EFI systems, which set me thinking about induction more generally. We inject fuel from a high-pressure common rail for many good reasons. We're capable of making stratified burn within a cylinder, provided we have full control of the throttle butterfly. We sometimes use exhaust gas recirculation to retard combustion and lower cylinder temperature. Given those scenarios, why don't we add a common rail of high-pressure atmospheric air, and use injectors to introduce air, and exhaust when required, in a similar way to fuel? Surely this would give me an engine that can respond quicker because there's no lag in the inlet airflow, have fewer mechanical parts and potentially reduce emissions by allowing me to control the oxygen content at the catalyst more easily?
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Simple reason: volume. @ 14.7:1 stoich, your input into the cylinder would need to be 14.7x bigger (or push that much more) through a nozzle than you would the fluid which is fuel. You state it would have fewer mechanical parts, but is that true? You'd have to furnish a mechanical method to create the high pressure air as well as introduce it into the system. You'd have to have some type of tank which would hold the high pressure air. Then that "high pressure" would need to be in the 3000-5000 psi range at a guess to ensure proper flow. Think of an air compressor which could keep up with the demand you are talking about. Let's say we throw some math in the mix (and assume I'm not just being completely stupid ... though the jury is out on that one): A 2L engine has a swept volume of 2L. If this theoretical engine was running, naturally aspirated and attained an 80% volumetric efficiency (VE), it would be taking in .8L of air every revolution of the crankshaft. The math: 2.0L X .8 = 1.6L - Intake volume for all four cylinders @ 80% VE 1.8L x .5 = .8L - Intake volume for every revolution in a 4 cycle engine 600rpm x .8L = 480L - Amount of air at idle needed to maintain idle speed 6000rpm x .8L = 4800L - Amount of air at redline to maintain fastest engine speed Your system would need to move 4800L of air per minute in order to maintain that engine speed. That's about 170CFM. If you can haul something like this: around on the back of your car, it might be doable. The 170CFM is a figure for the small, lower horsepower end of the equation. What about performance cars where you have three times as much swept volume (6.3L Chevrolet LT1 engine) with a greater VE (~85% at a guess). Those numbers are hugely greater. You'd be tripling the amount of air needed, which means triple the amount you'd be towing behind the vehicle. Yes it could be done, but at what cost? The way air is introduced into the engine now is far more efficient and introduces far more air than you could reliably continue to pump air into an engine the way you suggest.
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|
35,985 |
My uncle says a driver advised him that whenever the car is parked, the wheels have to be aligned with the body of the car, or else there will be un-necessary weight on (I think) the axle or wheel, which reduces the life of the parts. So is it really bad to park with the wheels at an angle as shown in the image below? Seems quite impractical to me, because while parking, the wheels inevitably do end up at an angle and a friend tells me the steering wheel should not be turned when the vehicle is stationary as that puts too much strain on the parts. Moving the car forward and backward just to get the wheels aligned expends extra fuel too.
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Not at all, in fact there are many occasions when you would want the tires at an angle to the body of the car. Any time you're parked on a hill it is prudent to angle the wheels of the car so that if the parking brake failed to hold the car would run into the curb. If the wheels were aligned with the body when parked on a hill the car would be free to roll down the hill until it collided with something. That could be bad… One more thing: if there is an increased load due to the wheels being turned, it is likely to be far less than the load imposed when the wheels are turned in normal driving (as then the car is turning and moving with forces imposed both by bumps and the act of turning). So even if the driver informing your uncle is correct about the load, it is unlikely to have a significant impact on the life of the vehicle – not to mention needing to balance that impact against the impact of turning the wheels while the car is stationary.
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36,115 |
I saw this poster at a tire shop earlier today As the image quality isn't great, I'll reproduce the advert's claims in writing: Take the lead! Ride smart! [Nitrogen] for your SAFETY & ECONOMY Nitrogen molecules are bigger than normal air Less leakage Fuel effecient [sic] Less irregular wear No presence of Oxygen No oxidation Longer tyre life No deterioration It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres! I would like to separate fact from fiction. Which of the above-mentioned claims would translate to practical, tangible benefits for road-going passenger vehicles?
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Summary The difference for passenger cars is pretty small, but it seems to be quite real. The less you maintain your tires the bigger the effect is. In large fleets of vehicles, the effect can be quite large. Get Nitrogen™ Further investigation of the site justinm410 linked to, getnitrogen.org , shows a number of studies that (assuming they're all legit) show some real difference between nitrogen-rich and regular air. With passenger vehicles, the fuel savings were between 2 and 8% depending on the study and driver behavior. A driver who regularly maintains their tire pressure sees much lower benefits than one who just gets the pressures checked during oil changes (about twice as much fuel savings if you only occasionally check pressures). One could argue that just checking your tires more often would save as much as nitrogen-filled tires, but the reality is that most people don't, so a public campaign to use nitrogen for tires could potentially see significant savings across a population. The biggest differences are seen on large fleets of heavy vehicles, where fuel savings were between 6 and 23%, and tire lifespan was increased anywhere between 40 and 86%. It seems that fleet vehicles aren't maintained as well as passenger vehicles, plus they have to survive most more strenuous conditions. There are two main causes for the savings. First, nitrogen-filled tires leak more slowly, so your tires will be closer to their correct pressures at any given point. I.e., if your tires are normally at 32 psi, the regular air might leak to 30 psi in one month, while the nitrogen is still at 31.5 psi. Second, nitrogen-filled tires see less variance in pressure during use. This lowered variance is mostly attributable to the lowered moisture, so a device to dry normal air might see similar results. There's also the issue of safety. A properly-filled tire will perform better, and with more predictability, than an improperly-filled tire. If the tire maintains a more consistent pressure, it follows that it will be somewhat safer, but there's no data on whether that difference is significant. Additionally, at least one of the linked studies cites "decreased number of blowouts" from nitrogen compared to regular air, but there's no information about how much of a decrease they saw. I don't have any way to verify the studies, but they've got papers from Bridgestone, Firestone, the Drexan Corporation on behalf of the Canadian government, among others. Plus Jay Leno says nitrogen is cool, and he's a celebrity, so obviously you have to listen to him. I tend to take a site's source material with a dose of salt until outside references verify it. But at face value, it seems to indicate the sign in the OP is basically accurate. Edmunds Edmunds.com investigates these studies, and concludes that while the studies are basically accurate, it's probably more efficient to just buy better tire-measuring equipment and get on it more often. Still that doesn't really mean anything for people who know they don't ever check the tires. Edmunds themselves did a study showing even "car people" really aren't as good about this as they should be. Many people, even at an automotive Web site like Edmunds.com, have never checked their tire pressure. This means the pressure is only adjusted when the tires are rotated, about once every six months to a year. This isn't often enough. Tires should be checked and adjusted at least once a month. We also found that many drivers don't know what level to fill their tires to. Many people thought the pressure was listed on the sidewall of their tires. This is wrong. The correct tire pressure is listed on a placard found in the car's door, doorjamb, glove compartment or owner's manual. Still more people seemed to be simply guessing how much air to put in their tires. They pumped air into their tires now and then to make sure they were over the required amount. But they didn't check and adjust the tires to make sure the tires were all approximately at the same level The Tire Rack The TireRack.com does their own study, where they conclude: Overall, inflating tires with nitrogen won't hurt them and may provide some minimal benefits. Is it worth it? If you go someplace that provides free nitrogen with new tires, why not? Additionally we've seen some service providers offering reasonable prices of about $5 per tire (including periodic adjustments for the life of the tire) to a less reasonable $10 per tire (with additional costs for subsequent pressure adjustments) or more as part of a service contract, which we believe exceeds the value of nitrogen's benefit. Rather than pay extra for nitrogen, most drivers would be better off buying an accurate tire pressure gauge and checking and adjusting their tire pressures regularly. Note that, again, their bottom line depends on drivers paying more attention to their cars. This is solid advice, but only helps if drivers follow suit. Otherwise, it seems nitrogen may be measurably better if it's cheap or free. Of note, both Get Nitrogen and Edmunds estimate about $100 a year could be saved with more consistent inflation. This means you'd still save some money, even with relatively more costly fill-ups. Response for the specific claims made Take the lead! Ride smart! Marketing hype, of course, but potentially accurate. [Nitrogen] for your SAFETY & ECONOMY Presumably safety is true, but it's unknown how true (even Edmund's other study isn't helpful here); the studies show economy is true, to some degree. Nitrogen molecules are bigger than normal air / Less leakage This paper explains that oxygen molecules have a slightly smaller "kinetic diameter", meaning they permeate through the rubber slightly faster than the nitrogen molecule. Since most of the non-nitrogen part of normal air is oxygen, this statement is true, if somewhat imprecise. Fuel effecient [sic] The studies on the site show this is true, citing from 2 to 23% better fuel economy. Less irregular wear It stands to reason less variance in tire pressures would lead to more even wear on the tire, but it's unknown if this is significant. No presence of Oxygen / No oxidation These are somewhat hyperbolic, but true according to the site's cites. Longer tyre life Shown by the studies to be true, citing 31 to 86% longer tire life, but these high numbers are for people who never check tire pressures and/or fleet vehicles. No deterioration Again hyperbolic, but possibly true if the "decreased number of blowouts" is significant, and is caused by deterioration rather than low pressure. It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres! It's probably a bit silly to compare typical passenger cars to heavy duty equipment or purpose-built race cars, but the basic premise behind the use of nitrogen in these fields still holds in the field of passenger cars, albeit to a much lower extent. Conclusion The sign is accurate, but the real-world effect is mostly very small for passenger vehicles in normal usage. If you're lazy about maintaining your tires, the real-world effect of nitrogen becomes more practically significant, though still small. Safety is some concern, but a difference of 1 to 2 psi isn't likely to be the difference between no crash and seventeen fatalities.
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36,415 |
From the point of view of mass, a smaller car appears to be a
disadvantage if in an accident with a bigger car, because the change
in momentum of the smaller car will probably be higher. A bigger car carries more material that can absorb energy via deformation upon collision (on the other hand, bigger cars have higher kinetic energy than smaller cars at the same speed). Is such analysis correct? (i.e. that bigger cars are safer) If yes, should it serve as a safety guideline when purchasing a car?
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In aggregate yes, however that's not the same as saying all large vehicles are safer than all small ones. The Insurance Institute for Highway Safety aggregates and publishes data about fatality rates in new vehicles in the US. You can see a general trend toward larger being safer, but bigger being safer is not guaranteed. The IIHS also publishes data about changes over time (available at the source); the short version though is that newer small cars compare favorably with older large ones. Driver deaths per million registered passenger vehicles 1-3 years old, 2014
Registered vehicles Deaths Rate
Cars Mini 1,131,535 62 55
Small 7,251,650 288 40
Midsize 9,700,209 335 35
Large 2,741,490 116 42
Very large 1,724,015 32 19
All cars 22,548,899 838 37
Pickups Small 777,825 32 41
Large 3,495,386 115 33
Very large 1,167,182 41 35
All pickups 5,440,393 207 38
SUVs Small 3,662,803 76 21
Midsize 6,509,578 102 16
Large 1,734,489 31 18
Very large 377,309 13 34
All SUVs 12,284,179 223 18
All passenger vehicles All 40,887,585 1,290 32 For anyone interested in more details of how it breaks down per vehicle, I've found a report the IIHS did in 2011 showing stats for dozens of the most popular vehicles. This can be read online, but is an electronic copy of something that was apparently originally a bound paper booklet. The middle column of the per vehicle model table is split between two pages and is much easier to read if you have a large display and can download the pdf and view two pages side by side. This is a noisy dataset (for many of the less common vehicles only a handful of fatal accidents are involved); but the spread within a single vehicle type is often larger than the spread between the averages for overall vehicle types. It's also several years old (2005-8 model years vs 2011-14 for the graph/table above). Even in such a short period of time you can see the overall improvements in vehicle safety, the 55 deaths/million vehicle years rate for mini cars from 2011-14 is about a third less than the equivalent from 2005-08 models, and comparable to mid/large size cars from the era. Over longer periods the overall improvement is even more dramatic. I made this graph from a table of data in the IIHS report linked to at the top of my answer. Modern vehicles of all types are roughly 5x less likely to kill occupants in accidents than they were 40 years ago. For SUV's its more like a 10x improvement; although that's mostly driven by massive improvements in the late 70s and early 80s that brought them inline with other vehicle types. Since then they've behaved more or less like any other vehicle type. You can also see the effect of electronic stability control becoming standard in pickup trucks at the end of the last decade as their survivability numbers improve significantly due to the reduction in rollover rates.
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37,289 |
I've seen a few vehicles with their plastic bumpers off recently. They all seem to have a large metal crossbar sitting in front of the radiator. What is this called? Update: And a sideview of the metal crossbar to impact absorber to chassis rail on an Audi A3.
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That is your actual bumper The bumper you have off is just a cover for your real bumper which is what you are describing. That bumper, the real one, is tied to your frame and is actually absorbing the energy from impact where the facade is just existing as a cover due to the ugliness of the actual bumper.
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37,308 |
Apart from the mandatory emergency gear that should be in cars (early warning devices, fire extinguishers, visibility vest, first aid kit) what other tools should I get? Flashlight Gas Container Should I get a tire pressure gauge or something? Are there tools which could help me diagnose problems?
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Aside from what you mentioned, I always carry: Portable air compressor (12v) Small tool set (common wrenches, screwdriver, grips, electrical tape and zip ties). A good flashlight Spare cellphone charger (both DC and AC if car does not have USB plug) List with emergency contacts in glove box. Rope in case I need to be removed from a ditch or towed (happens more than I'd like to admit). Copy of keys to open trunk and doors on wallet. Money in trunk inside plastic bag ($100 is good). Jumper cables that are are at least 3 meters long. Towel Spare change of clothes (includes shoes and socks) A bat or something to defend yourself in case of zombie apocalypse (or anyone tries to hurt you and you can't run). I'm a bit obsessive about this, but these are things I've needed over the years (including the bat).
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37,628 |
I've noticed that in a manual transmission vehicle when going uphill I have two options: Downshift and press the gas more Stay in the same gear and press the gas more I haven't measured it but typically in the higher gear I end out flooring the throttle, while the lower gear I don't need to go quite that far. Am I wasting gas if I stay in the higher gear, or is the engine just not able to consume that much so I'm just making a bunch of gas available, but the engine just doesn't suck it in?
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Bear with me, I'm going to clear up a myth, then answer your question. You will see that they are related. Higher throttle doesn't mean higher RPM. Higher throttle just means more fuel entering the combustion chamber. This will tend to accelerate your engine, but if it's under an accelerating load (increasing incline) at a constant gear, the engine will not necessarily accelerate. It will, however, burn more fuel. That being said, when you downshift, your engine does more Rotations Per Minute. It is now bringing less fuel into the combustion chamber, but it's bringing it in much more often. All this means that when you are running under a load, you basically want to be running the engine at the balance point between entering tons of fuel into the combustion chamber at very low RPM and entering tons of fuel into the combustion chamber at very high RPM. For most cars, that point is between 1,500 and 3,000 RPM. In other words: your fuel efficiency doesn't just have to do with higher vs. lower gear: it has more to do with your proximity to your engine's optimal RPM. Exception case is when you are not running under a load (accelerating, climbing a hill). When you are on flat ground or descending a hill, you want the lowest RPM possible.
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37,718 |
I've been keeping track of the fuel my car, a Ford Fiesta Ecoboost 100 hp, uses since the day I got it. In the last three years I've owned it, I've noticed a large (>20%) difference in fuel consumption between driving in winter and driving in summer. My driving patterns are identical in winter and summer, yet my fuel consumption is much higher in winter. I understand that cars have slightly more power when cold, but is the difference that big? Fuel consumption in liters/100 km:
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Your fuel economy change is caused by the fact you're not using the same fuel. Fuel changes twice per year from summer blend to winter blend and back again causing a change in the Reid Vapor Pressure (RVP). In summer, the hotter temperature evaporates liquids easier causing more pollution, so it is blended to lower the RVP. This blend is more costly to produce. While in the winter time, the RVP can be much higher so additives such as butane are used. While this lowers the manufacturing cost, it also burns more quickly resulting in a hit on the MPG fuel economy.
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38,032 |
I have heard really mixed opinions about the necessity of engine flushes. My quick research suggested that manufactures do not recommend doing them. In addition, I have heard of extreme cases of blown engines after engine flushes. My mechanic performed an engine flush on my old car and so far, it seems to be ok. Is it safe? Is it necessary? What are the pros and cons of doing it?
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An engine flush is basically the process in which a mechanic puts chemicals in the engine oil to break down sludge or carbon deposits from old oil. The difficulty with it is that it can break down sludge that had formed over rubber seals and is actually serving as a secondary engine seal. Furthermore, if your engine has had regular engine oil changes at the specified times, a flush should be totally unnecessary. If you do have serious sludge build-ups, it could be the best route to take; but you're taking it at a risk. If the sludge is actually protecting the rubber gaskets, you may have a bigger job on your hands replacing them.
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38,194 |
I would like to know the proper oil to use in a Ford GAA engine from around 1945. Could be as late as 1958. From a series of photos of a GAA being restored on Flickr . Currently this engine has all the original seals and gaskets and showed no signs of leaking when I got it. I do know the bearings are silver babbitted and the block, heads, and covers are aluminum. It has brass cam gears and a gearbox upfront to run the magnetos water pump PTO shafts and cam drive shafts. I am thinking this is going to be a pretty heavy oil maybe a straight 50 weight or something but not sure. I have not found any parts list that has a part number specifically for this engines oil. I do have a copy of the GAA / GAF / GAN service manual but any other documentation would be great.
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Per @Eric Urban's suggestion, I found the Technical Manual for the M4A3 tank published in 1942. That tank did use the aluminum Ford GAA 18L V8 engine which produces 500 hp at 2600 RPM! It says: Capacity: 32 Quarts Above 32°: SAE 30 32° to 10°: SAE 30 or 10 10° to -10°: SAE 10 Below -10° : Not Listed Replace the oil every 50 hours or 500 miles on dirt roads or 1000 miles on paved roads. (These are miles in a tank .) Clean the oil filter every 1000 miles. I believe @user23543 has a point that oil formulations have changed over the years. In 1942, the SAE J300 standard was much different. It was only concerned with one viscosity and tested that in a much different way than today. They used a different test apparatus and different temperatures. Some say, "the minimum standards for each grade have only become more
demanding [over the years]" . That's a good general rule, but it's not that simple. SAE J300 started out measuring just one viscosity of the oil with a "crude" apparatus. Nowadays, SAE J300 prescribes the grades by listing the viscosity under several different conditions. Today's oils are probably overall better than back then, but since we do not know the other viscosity numbers from back then, we cannot make a full comparison. I have been unable to find the revision year of SAE J300 that was applicable in 1942. I have also been unable to obtain a copy of the original SAE J300 standard published in 1911. The original SAE J300 compared all oils the same; it did not break "oils" up into the various categories we have today. Illustrative points: Prior to 1947, oil was not divided into Regular Type (mineral oil), Premium Type , and Heavy-Duty Type (contains detergents). ( source ) Prior to 1952, oil was not divided into gasoline and diesel engine categories. Even then, that was part of the API standard, not SAE J300 . ( source ) In 1952, SAE added the winter ("W") grade. ( source ) The viscosity of SAE 30 back then and the viscosity of SAE 30 now are similar, but not identical. I have no information on any of the other properties that we take note of today from the oil back then. SAE 30 is a good starting point though.
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|
38,195 |
When a vehicle's alignment is off, people say the car "pulls" to one side or the other. However, if you've never gotten to feel a bunch of cars in varying states of alignment, it's hard to tell whether there's too much pull. How much pull is acceptable before the damage you are doing to the tires warrants going to get your alignment adjusted? If I try to let the car go where it wants to go, the result is quite varied. Presumably this is related to the state of the car when I let go. When trying to gauge alignment, is it best to use my best case, worst case, or average case behavior? How straight is "good enough? For perspective, my best case scenario let me drive about a quarter mile while letting the car do what it wants before I got close enough to leaving my lane that I chose to intervene. My worst cases started to leave the lane in the range of 5-10 seconds. I definitely notice a preference for the car leaving the lane to the left. Should I assume that is my car's alignment, or is that something which could simply be a side effect of how I, as a person, choose to center the vehicle in the lane before testing? A related question: Wheel Alignment: Just how bad is bad? (but in their case they are taking measurements off of the car directly. I'm looking more for heuristics).
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Per @Eric Urban's suggestion, I found the Technical Manual for the M4A3 tank published in 1942. That tank did use the aluminum Ford GAA 18L V8 engine which produces 500 hp at 2600 RPM! It says: Capacity: 32 Quarts Above 32°: SAE 30 32° to 10°: SAE 30 or 10 10° to -10°: SAE 10 Below -10° : Not Listed Replace the oil every 50 hours or 500 miles on dirt roads or 1000 miles on paved roads. (These are miles in a tank .) Clean the oil filter every 1000 miles. I believe @user23543 has a point that oil formulations have changed over the years. In 1942, the SAE J300 standard was much different. It was only concerned with one viscosity and tested that in a much different way than today. They used a different test apparatus and different temperatures. Some say, "the minimum standards for each grade have only become more
demanding [over the years]" . That's a good general rule, but it's not that simple. SAE J300 started out measuring just one viscosity of the oil with a "crude" apparatus. Nowadays, SAE J300 prescribes the grades by listing the viscosity under several different conditions. Today's oils are probably overall better than back then, but since we do not know the other viscosity numbers from back then, we cannot make a full comparison. I have been unable to find the revision year of SAE J300 that was applicable in 1942. I have also been unable to obtain a copy of the original SAE J300 standard published in 1911. The original SAE J300 compared all oils the same; it did not break "oils" up into the various categories we have today. Illustrative points: Prior to 1947, oil was not divided into Regular Type (mineral oil), Premium Type , and Heavy-Duty Type (contains detergents). ( source ) Prior to 1952, oil was not divided into gasoline and diesel engine categories. Even then, that was part of the API standard, not SAE J300 . ( source ) In 1952, SAE added the winter ("W") grade. ( source ) The viscosity of SAE 30 back then and the viscosity of SAE 30 now are similar, but not identical. I have no information on any of the other properties that we take note of today from the oil back then. SAE 30 is a good starting point though.
|
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|
38,809 |
I've noticed that engines are rarely exactly 1.5 liters or exactly 4.0 liters, and I'm okay with that. It makes sense that engines would have some arbitrarily ideal size for specific applications, so I would expect exact engine displacement to be all over the place. But it doesn't usually seem to be. Nissan's VQ35DE is 3,498cc, Toyota's 4U-GSE is 1,998cc, and BMW's N52B30 is 2,996cc. Why aren't they just 3,500 cc, 2,000 cc, and 3,000 cc respectively?
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There are regional taxation and tariff issues associated with displacement Manufacturers will intentionally keep their displacement just under a limit that may increase their local/regional taxation as well import/export tariff regulations in accordance with trade agreements, etc. It's easy enough to make an engine exactly 3 Liters. Math is exact if you want it to be. Manufacturers will intentionally 'fudge' the numbers and round up for advertisement/marketing. 2 CC is a nominal fudge and a barely measurable performance increase and IMO not a misrepresentation.
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39,007 |
I've been told that reverse is the "strongest" gear, so in a manual transmission vehicle you should park your vehicle and leave it in reverse in the event of a parking brake failure. Others have said first or second gear are fine as well. Is there a "best gear" to leave your manual vehicle in when parking it?
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The lower the gear, the better the job the engine compression will do at holding the car if the brake fails, that's because a lower gear makes the engine spin faster and requires it to do more work for the car to move. So 1st is better than 2nd, between reverse and 1st it's not so obvious – but from the examples people are finding it looks like 1st is a bit better. Bottom line, 1st or reverse, leaning towards 1st.
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39,014 |
If the purpose of the rebuild is to bring the engine back (or as close as feasibly possible) to its original performance, what are some things that should always be replaced? This obviously depends on the condition of the engine, so let's say a 300,000 km engine which has had regular oil changes its whole life. Gaskets, seals, belts, bolts, etc. yes you should replace, but how about components such as valves, valve springs / hydraulics, piston heads, connecting rods, camshafts, piston rings to name a few?
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If the intent is strictly to rebuild, here is a list of items which should always be replaced : Rings Compression rings Oil control rings Bearings Main bearings Rod bearings Cam bearings (not always needed, but good choice if equipped) Freeze plugs in block Head bolts (if torque to yield type) Gaskets Seals Absolutely needs done Block Clean all threads (chase with tap) Brush all oil galleys Hot tank If not boring, hone cylinders to break the glaze (allows for proper ring seating) Clean all surfaces to remove gaskets and any other materials Parts to consider reconditioning or replacement Block Bore/hone cylinders (ring ridge, out of round, tapered, scoring) Deck (check for flatness, machine if needed) Main bores (align hone will ensure no crank binding) Crankshaft Rod journals (check for out of round, machine if necessary; polish at a minimum) Crank journals (check for out of round, machine if necessary; polish at a minimum) Check for warpage; replace if necessary Head Check for flatness; resurface if necessary Check valves for sealing; valve job and lap if necessary Tins (oil pan, valve covers, etc) Check all to avoid leaks when resealing Pistons Clean if not boring cylinders Replace if boring cylinders You can also look at things like injectors for reconditioning, but those would be further down the list.
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39,183 |
As I know, clutch pressing and neutral gear both disengage the engine from wheels. So will it matter if I do not press the clutch if I start in neutral?
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It depends on the specific vehicle. Many modern standard transmission cars in the US have a clutch pedal sensor that will not allow you to start the vehicle if the pedal isn't fully depressed. You'll turn the key and nothing will happen. I've had older vehicles that preceded this sensor that could move the vehicle if the clutch was engaged and the transmission in gear. This was cited as an emergency way to move the vehicle (e.g., if you stall on railroad tracks).
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40,111 |
I was wondering why a manufacturer would detune an engine. An example -- there are many others -- is the Mercedes-Benz OM612 engine . Same engine, lower (peak) power output in the Sprinter than in the E-class. The same hardware (and thus the same cost), yet they 'artificially' lower the power output and thus the specs they can use to sell the product. Does it have to do with using the same engine for different purposes? With a van you probably want a different power and torque curve than with a sedan. In the example I gave, that seems to be the case, with the van reaching top power and top torque at a lower rpm than the sedan. Or are there other reasons (fiscal, strategic,...) that lead to these decisions? Using the same example, in Belgium the engine was detuned whereas in other countries it was not (both for the same cars), as can be seen in the Wikipedia page. I live in Belgium but I have no idea why they would have done this for Belgium specifically. In this case, the only difference is the peak power output, the rpm at which this occurs and the max torque is still the same. If non-design reasons are involved, would it (sometimes) make sense to tune these again to their 'normal' specifications?
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I'd be tempted to restate the question as "How do vehicle manufacturers decide what to tune for?" For the question as asked, there are a lot of possible reasons, and probably no way to know in a specific case unless somebody involved speaks up, but in general: To match the engine to a specific use case (as you suggested here). To find a balance between performance, durability, and marketing needs (detune in Sprinter to improve reliability, tune in E-class for marketing/performance). To fit into a particular regulatory class (in the US, for example regulations change with the load capacity of a vehicle). To meet insurance requirements (horsepower limits for example). To balance "fleet" requirements (another example from the US, makers are rewarded/penalized on maker's overall averages for fuel consumption and maybe for emissions as well, so tuning may get tweaked to manage this). Maintaining or adjusting a product "line" – a maker may want to have a "logical" progression of features or performance and so adjust numbers to make this happen, or may be trying to move customers for strategic or economic reasons. For an operator of the vehicle it would seem that, after evaluating the "good" reasons for the tuning decisions, there would be no reason not to adjust the tuning to suit the operator's needs.
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40,792 |
I saw a lot of YouTube videos referring to crankshaft grinding, while watching videos about working on crankshafts. I don't understand what crankshaft grinding does. If we grind a crankshaft, then how does it stay compatible with the vehicle where the crankshaft was taken from? If it is to make it lighter, then doesn't it invalidate the crankshaft maker's purpose of making it thick and heavy?
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Grinding a crankshaft is a process of removing material from the journals in an effort to refurbish and reuse an expensive, yet vital component of an engine. It is usually done during the process of rebuilding an engine when needed, but also has some performance aspects which come along with the process. Let's first off describe the anatomy of a crankshaft. The different parts of the crankshaft are: Main journals Rod journals Snout (or nose) Flywheel mounting flange Throws Counterweights Web The main parts we are working with when grinding are the journals, both main and rod. During the rebuild process it will be determined if the journal surfaces are within sufficient tolerances to be used as they are or if they will need to be ground. There are several reasons why they may need to do the machining: If the surface of the journal has wear which makes it no longer smooth If the journal is out of round If the journal is not square (same diameter at both ends of the pin) Can also be ground to create more stroke (this would make for another answer, so will not include the details here) If the decision is made to reuse the crankshaft, but machining will be necessary in order for it to work, the machinist will grind part of the top layer of the journal away to make it smooth again. Usually (in the SAE world), the amount taken off is measured in 0.010" (usually 0.010", 0.020", or 0.030" - depending on the severity of the wear on the journal). Once the journal is ground down close to the final dimensions needed for the process, there is then a finishing process of polishing the journals. This involves using using a long circular piece of emery paper. The process looks like this: The crankshaft is spun while in the opposite direction and the emery paper is put in contact with the journal. This process creates an ultra smooth surface on the crankshaft, which reduces friction, which improves overall power and torque. To get the crankshaft to work once again in the engine, you have to take up the excess space which is taken away during the process. This is done by using under-sized bearings (undersized because you are making the journal smaller, not larger - the bearings are matched undersized by negative numbers to match). The bearings are matched to maintain the proper clearances for oil flow at the new diameter of the journal. The main reason for grinding a crankshaft is as stated, but there are some side benefits to doing the grinding. First, yes it does lighten the overall weight of the crankshaft, but overall it doesn't do that much to create a huge difference. If you wanted to reduce weight, you'd do things like drill the pins and other things which are better left for another question. Second, grinding the journals and reducing their overall size. By reducing the size, you have less surface area. Reducing the surface area reduces friction losses imposed by the journal faces. The difference is measurable on an engine dyno. If you are an engine builder doing a max effort, this is definitely one area to look at for creating greater efficiencies and thus making more power/torque. Third, the grinding process also makes the corner of the journals so they have a greater radius. This actually makes the crankshaft stronger by reducing the stress riser at the corners. There are other reasons which I may not have covered, but I believe I should have answered your question.
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41,509 |
In a lot of the cheap cars I have looked at their exhaust components, I always find the catalytic converter right after the exhaust manifold instead of being after the down/front pipe in a "typical" exhaust setup.
Why do cheaply manufactured cars come like that, what kind of gain putting the cat right after the manifold can the manufacture make other than having shorter wires for the o2 sensors? Or am mistaken and those cars come with two cats like I have seen in some other cars?
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The main purpose of putting it right after the manifold is heat. The cat functions best when hot. Placing it as close as possible to the manifold helps the cat heat faster and stay hotter, which produces better results in what it's designed to do: curb exhaust emissions.
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41,731 |
Since the entire job of an internal combustion engine (ICE) is to turn heat into mechanical energy, why aren't electric heating methods more popular? I know there must be a reason. I'm not talking about electric cars or anything, but using electricity to heat up and do work.
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Because it wouldn't be very efficient. The main advantage of internal combustion engines is that the energy density of their fuels (gasoline, diesel) is very good. You can go a long way on a relatively small, light tank. The drawback of them is that they aren't very efficient. Most of the energy in the fuel is lost to friction and heat, and only a very small portion (<35%) actually turns into mechanical motion. Electric vehicles are great because they are incredibly efficient. The fuel they use (batteries) is no where near as compact and light as gasoline or diesel for the amount of energy they store, but an electric motor can turn 90%+ of that energy into mechanical motion. Using electricity to heat air and run an engine based on the pressure change would be combining the worst aspects of both these system.
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41,740 |
I have a VW Polo 2003 1.2 and would like to add a speaker to each rear door. I am a complete newbie when it comes to electrical work in cars (actually in most things about cars other than the important simple stuff I suppose). Currently the car has 2 front speakers. I have taken apart one of the rear door trim panels and noticed there is a space where a speaker could be added, however there was no wiring available other than the one that goes to the central locking (I think). How would I go about passing the speaker wires to the Sony stereo? I was thinking of passing the speaker wires along with the wires that seem to be for the central locking. I assume that doing this would allow me to collect the speaker wire under the front passenger seats. However I am not sure where to go from here to reach the main head unit whilst keeping the wiring well hidden. Where would the extra speaker wire then be connected to the stereo? I have noticed that there are various harnesses at the back of the stereo. also the head unit has several holes where RCA cables could be plugged into. I haven't bought any speakers yet and I want to be sure what i need to do before buying them. How do speaker wires look out of the box generally speaking (description is enough)? Thank you for your help
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Because it wouldn't be very efficient. The main advantage of internal combustion engines is that the energy density of their fuels (gasoline, diesel) is very good. You can go a long way on a relatively small, light tank. The drawback of them is that they aren't very efficient. Most of the energy in the fuel is lost to friction and heat, and only a very small portion (<35%) actually turns into mechanical motion. Electric vehicles are great because they are incredibly efficient. The fuel they use (batteries) is no where near as compact and light as gasoline or diesel for the amount of energy they store, but an electric motor can turn 90%+ of that energy into mechanical motion. Using electricity to heat air and run an engine based on the pressure change would be combining the worst aspects of both these system.
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45,137 |
So let me preface this by saying that I follow all of the manufacturer's suggested maintenance and religiously get my oil changed every 5K miles. However, my 2007 Mazdaspeed6 is about due for its 120k mile service, and for the last few weeks I've noticed this weird quasi rattling sound when I would start it up first thing on the morning. It would persist under low rpms and under load for the first ~5 minutes after I'd start the car and then eventually go away. Yesterday I realized that it sounded a lot less like a rattle and more like metal-on-metal noises, as if engine components weren't being properly lubricated. I checked the dipstick and it was BONE dry; absolutely nothing came back on it. I had a couple quarts of oil in my garage and dumped three in. This seems to have taken care of the noise I was hearing, but now I'm wondering how much damage has been done (and also how I burned through so much oil so quickly, and why the light never came on). I already had an appointment scheduled with the dealership to have this noise diagnosed, but is there anything I should have them check while it's there?
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It sounds as though you were low on oil, but not out of oil. Your MS6 requires around 5.5-6 quarts of oil, so if you dumped three quarts in to get it up to level, you still had nearly three quarts in it. While this isn't optimal, it's definitely not bone dry. This is part of the reason your oil light didn't come on. That and the fact most "idiot lights" don't come on until the pressure gets somewhere in the 5psi arena. Lower oil quantity will usually spell lower oil pressure, but it doesn't mean there was absolutely no oil pressure. Like I said, this isn't optimal, but would probably preclude a bunch of engine damage. Rattling parts inside the engine is never good, but some oil pressure is much better than no oil pressure. You most likely have gotten away with very little engine damage, but probably have shortened the longevity of the engine some in the process. In this case, you're probably better off not "crying over spilt milk" and continue to drive it like you always have ... well, maybe you should check the oil a little more often :o) As for the oil usage, it could be coming from several different locations, but it seems the people on this Mazdaspeed forum say there could be oil usage at the turbo. It seems the MS6's turbo may have oil consumption at the turbo bearing. I'm not sure if it could account for the amount you're talking about, but you also hadn't stated the last time you'd checked the oil in the engine. The engine has lost however much oil it's lost since the last oil change. The problem may be the turbo bearing like the forum talks about, or it could just be an old fashioned leak. To check for leaks you'll need to get on, under, and around your engine and see what's going on. Also look to see if there is any spotting in the drive/garage floor which might indicate such an issue. If you don't see any obvious oil leaks, let the dealership tell you if they see any. This is a double edged sword, though. Some dealerships are unscrupulous in if you tell them about your overall issues in detail, they'll tell you the car will need a new engine. The only reason being to pad their own wallets due to an unsuspecting customer. Be careful what you tell them, but give them enough information they know what to be looking for ... like I said, a double edged sword. Have them at least check for oil leaks. Ask them if to check the function of the turbo, maybe. Leave it up to them to give you the skinny, but don't lead them down a path which includes engine replacement, as I don't think your Mazda is due for one yet.
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45,749 |
These appeared on my rims after taking my bike to a repair shop. Does anyone know what these are and how to remove them?
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Those are wheel weights. They are to balance out imperfections in the weight of the tire to avoid vibration at speed. I would recommend not removing them. If you're concerned about them standing out against the tire, you can remove them carefully with a flathead screwdriver, scrub off the remaining adhesive, and replace them in exactly the same spot with exactly the same number of weights of the same weight per weight of a different color (i.e. black) or paint them.
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47,662 |
I wonder why a car has 4 wheels but has only one spare wheel. Is it that only one tyre can puncture at a time? If not, what if more than one tyre punctures on the go?
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Many modern cars have no spare wheel at all. BMW have recently started implementing run-flat tyres across the range. Tyres which can, even with a puncture and no air pressure, be used at a reduced road speed. Some other manufacturers have begun to include a compressed can of "tyre weld" or similar which attaches to the valve of a flat tyre and injects a sealant foam, again so the vehicle can be driven at a reduced road speed to a tyre bay for proper repair. Carrying a spare wheel is quite an expensive business. It's expensive from a perspective of space, it's expensive from a perspective of weight and its expensive from the added production costs. However, generally a single spare is seen as a good compromise. There is nothing to stop a multiwheeled vehicle picking up more than one puncture at a time but this is an unlikely scenario. Continent crossing vehicles (such as Dakar rally cars) will generally carry multiple spare wheels strapped to bonnets, roof bars or on the tailgate. This is because they may have to travel hundreds of miles before finding a garage. For most consumer vehicles, they're usually never more than a few miles from a town or village with a tyre bay. Also, they're usually used on roads where busses operate and mobile phone coverage is good. If you were unlucky enough to have two punctures, the likelyhood is you can call a local garage, continue your journey on the bus or at worst case, have to flag down another passing car. I should add that the most common reason why a four wheeled vehicle requires two tyre repairs is that a puncture has happened and the owner has found that the spare is also flat.
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47,903 |
On my car there are these strange wires sticking out my tyre. They are wedged in the tyre at one end, and I pulled a few out before taking the photos below, before getting one stuck in my finger... Ouch :( The tyre isn't bald as I still have loads of tread in the middle and other side of the tyre. On the outside of the tyre, inside the treads there seems to be many small cracks. Can I get these wires removed? Should I change the tyre?
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These wires are probably the wires in the steel belt of your radial tire. If you see those wires, the tire is worn out. You should replace it today! No, you should have replaced it yesterday! For information about how a radial tire is constructed, see this Wikipedia page: https://en.wikipedia.org/wiki/Radial_tire
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|
48,931 |
I drive a 2016 Scion FRS, and based on the maintenance schedule of the coolant: 1st replacement interval is 11 years/137,500 miles (220,000 km).
2nd replacement interval is 6 years/ 75,000 miles (120,000 km) after the 1st. ...I don't really understand the point of replacing the coolant. Why would it need to get replaced if you're constantly replenishing it? Especially during a long period of 11 straight years, wouldn't it have been replaced several times over? Edit #1 I said "constantly replenishing". Constant could be any frequency. The definition of constant means occurring continuously over a period of time. So let me be specific, "topping off when needed". Also my car is still relatively brand new, under 10k miles. There aren't any signs of leaks that I know of, so it's doubtful I have a leak. I already answered my own question prior to looking at any of the answers here, but correct me if I am wrong. Basically, by "topping off", I am diluting the ratio of impurities to non-impurities in the coolant solution, but I am never removing the impurities themselves. When coolant gets used, it evaporates, leaving the impurities behind, so replacing the entire supply of coolant is necessary as a method to carry away the impurities. The only person who came close to this answer is user33191.
|
The logic behind replacing the coolant, rather than just topping it off, is to remove impurities. If the reason you have to add to it is that there is a slow leak somewhere, you may get by with just adding some now and then. But if the nature of the problem is that that coolant itself is being depleted, without removing any impurities, then yes, it has to be replaced. What does it look like when you drain it off? Does it look like fresh coolant?
|
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|
49,333 |
Are there any mechanical / safety issues arise when you do not put trims on car tires? Even when using the car in winter temperatures? (Say -15C to -20C)
|
No, hubcaps are purely cosmetic and do not need to be fitted. Some designs improve fuel economy and reduce wind noise by having a fairly flat surface but a car with one or more missing hubcaps is perfectly safe and in the UK, for example, hubcaps are not required to pass the annual MOT (safety inspection).
|
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|
49,367 |
Is planning a regular rotation of new tyres over their lifespan a good or bad plan? From many posts I've seen here and elsewhere on the web, motorists in the USA seem to see rotating tires as a task which ought to be undertaken at regular intervals. By rotating tires, I mean moving their position on the vehicle, so moving them from the front to rear axle for example. In the UK, we seldom do this. Indeed one of the biggest tyre fitters in the country actually advises against the practice (see link here ) I've just fitted a set of four tyres to our 2012 VW Golf and wondered if it is worth rotating them over the life of the tyres. Is there any advice that is clearly for or against the practice and are there any studies which back this up?
|
tl dr: Kwik Fit is full of crap. It's good to rotate tyres (and tires, too :o). The entire idea of rotating tires is to keep the wear relatively similar (or even), front to rear. If rotation is done at the specified intervals, the only time you'll have a weaker tire of appreciable wear is when it's time to replace all four. I don't know what the end goal of Kwik Fit is, but there are several things they state on their website which are VERY disturbing to me having to do with tire (tyre) rotation. Here is what I'm talking about. Note: I'm taking quotes from the page you linked. Partly worn tyres are more likely to experience punctures – particularly in wet weather conditions. What does wet weather have to do with whether a tire is punctured or not? Absolutely nothing, as far as I can tell. Road hazards will flatten a tire just as quickly in dry weather as it will in wet. Front tyre deflation will create an under-steer effect which is easier to control than over-steer (the effect produced by a rear tyre deflation) Understeer by definition is: "(with automobiles) having a tendency to turn less sharply than is intended". Does anyone believe if you have a sudden tire deflation on the front end you are going to be able to turn the vehicle more sharply than if you lose it on the back end? I certainly don't. In the unlikely event that a tyre deflates suddenly, then it is easier to control the vehicle if this occurs at the front of the vehicle. For improved handling and stability it is now recommended that the ‘best’ tyres should always be fitted at the rear of the vehicle. This is irrespective of whether the car is front or rear wheel drive. ~70% of the braking power and most all of the steering power is controlled from the front end of the vehicle. If you suddenly lose air pressure in a front tire, you've now lost a major portion of both, which means you've lost a major amount of control of the vehicle. This is especially true if you are traveling down the motorway at 70mph (which I believe is the typical posted speed on the M1, right?). By having a blowout on the rear of the vehicle, you maintain almost all of your braking power and lose very little of your turning power (rear might want to drift some). If you lose a front tire, it will drag the car in the direction of the lost tire. If the pull is great enough, it can most likely cause an accident, either through dragging the car into other traffic or causing the driver to lose control and creating a single car accident. It seems to me this tyre company has an agenda. One in which they want their patrons to wear out their tires faster, so they'll come back and buy more tires. Having the weaker tire on the rear of the vehicle is not going to create as big of an issue as having it on the front. Other things they state there on the website are accurate. You don't rotate tires on a vehicle where the front and rear are different sizes (like you'd see on some sport vehicles). I have never seen a car which has a specification for asymmetric tread pattern at one end of the vehicle and symmetrical at the other, but I guess there could be. In this case, you don't want to rotate the tires, either.
|
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|
49,902 |
Can we use Neutral (N on the selector) instead of Park (P) when parking on a flat surface? Is this useful for transmission system? Because every time we put gear on P we must pass through R and will this reduce gearbox/clutch's life? What is the mechanical difference between Park and Neutral? I think Park is basically neutral, but with a parking pin locks the wheels from moving... so when surface is flat we don't need that pin and using handbrake is enough. What do you think?
|
Depends on the car.. some won't let you remove the key from ignition if it's not in park. To be honest I really wouldn't worry about "crossing" reverse when heading for Park there is usually a slight delay before it engages the clutch anyway so when moving the selector you will be past it and into park before it does anything about selecting reverse. "Park" is, as the name implies what it's designed to be put in when parking up so it's a safe bet that that's a good course of action.
|
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|
49,994 |
Sometimes when waiting for a traffic light, I see the reversing lights on the vehicle in front of me briefly flicker on and then off again. Most often, this is on Mercedes people vans (short buses). This startles me, since if the vehicle were to be put in reverse by accident, it would hit me when trying to drive away when the light turns green. But it always turns out to be a brief flicker of the reversing lights. What could be the cause of this? Is the driver doing something wrong, accidentally putting it in reverse? Is it faulty wiring?
|
It's simply because some cars will illuminate the reverse lights when the drive moves the gear selector from D, through R on their way to P when stopping for extended periods. My Porsche, and my Range Rovers before only showed the reversing light when the gear was actually engaged. Other cars seem to have the light wired to the gear selector position. It's only a cause of concern if the light stays on, at which point you try and work out whether the car in front is more expensive than the car behind you while leaning on the horn.
|
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|
50,173 |
Somehow I was lucky enough to hit something when going downhill. And now my tire looks like in the picture. So should I still drive with this tire or get it replace immediately? And to replace it, is it safe to drive to the tire shop, which is a few miles away?
|
Sidewall damage is a serious issue. Sidewall is the structural part of the tire, and damage to it can result in dangerous consequences. Replace your tire immediately. If you know how to put the spare tire on (and there is a spare tire in your car), please do it now, and drive only to the tire shop. Spare tires are not designed for extended drives, so don't start driving around in the spare tire. If you have driven more than a few miles already with the tire before looking at the damage, you may have enough data to indicate that it may survive to the tire shop. I would however prefer the spare tire approach in your case. If there's no spare tire, then that would be a difficult decision: to have your car towed with the broken tire off the ground, or to drive the car. You know more about the details in your case than I do, because you didn't indicate how many miles exactly you drove with the tire after the incident.
|
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|
50,816 |
Last night I ran over a bolt and it went straight into my front passenger tire. The shop that I usually take my car to for repairs is about 8 miles away (if I take no freeway), 7.5 miles away by freeway. The tire has sat for about 15 hours so far and does not seem to have lost any air and I can't hear any air escaping from it. Here is a picture of it: So, is this safe to drive on to get it to the shop? Thanks!
|
Honestly, it would be best to put on a spare. Chances are you could make it to the shop with no problem, but there's an increased risk. The tire could rip and rapidly deflate, or it could leak fast at an moment and leave you with less control than normal. Usually you would just pull over with no danger, but now what? Change your tire in the middle of the road? If you have no spare, drive on the least busy streets as possible, and go a reasonable speed and be ready to pull over any second. Keep your distance and plenty of braking room, etc. If you have a spare, another bonus is that you don't have to wait at the shop to get your tire fixed. You can drop off the wheel and have them fix it while you shop nearby or something. I normally take a tire off to have it fixed even if its just a nuisance pinhole because it's easier for me to drop it off and pick it up hours later or even the next day.
|
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|
51,426 |
Q - why is the circuit described below protected with a 40amp fuse when the cable to the motor is 2mm² (I cut a bit of cable out and measured strand thickness and quantity, 37 * .26mm = 1.98mm²) and therefore likely rated for 25amps max. (All the vehicle wiring shops, that I've looked at, list 2mm² thin wall cable as rated for approx 25amp max.) Am I misunderstanding something about the max rating? Background to question - I was planning on wiring the motor direct as there is a fault somewhere (tested motor, relay, fuse and resistor pack and they are all good) and I don't want to pull apart dash to find offending wiring but this has stumped me as I assumed I'd need 6mm² cable to match the 40amp fuse but manufacturer uses only 2mm². I guess the motor may well be drawing considerably less amps (not tested) but then the question still remains why use a 40amp fuse. Thanks in advance.
|
The maximum rating of 25A will be for continuous use. The 40A fuse is there to blow very quickly in a fault condition. If you look at this page https://en.wikipedia.org/wiki/American_wire_gauge 2mm² wire will take 166A for 10 seconds or 633A for 1 second before it will fuse. So the 40A fuse will have blown long before the 2mm wire will fail.
|
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|
51,583 |
"If a jack can lift a load, surely it can withstand the load for extended periods of time?!" I've come across some conflicting ideas regarding this subject: The user guide for my low-profile hydraulic jack warns against using it as a stand for static load-bearing duty. Paraphrased, it says that the jack should be used for no longer than necessary and should not be used for extended periods of time. I frequently see roadside mechanics using these jacks to raise vehicles while they work on them (not that I deem them to uphold standards of safety, but it seems to work for them). These jacks are typically designed such that it is difficult to release them accidentally. Unless the seals in the jack are shot, I don't see how the load would cause the jack to "sag" over time. Is there some unbeknownst-to-me reason which explains why a jack makes for a poor stand?
|
There is no such thing as "absolutely, perfectly, 100% safe." Each tool has its proper and improper uses, and each works either in parallel with other tools to increase safety and dependability, or in series with other tools ultimately reducing safety and reliability. Will a hydraulic jack hold up a car safely? That depends on the level of risk you're willing to take. In a hydraulic jack there are several failure modes: Structural failure (metal fatigue, fastener failure, weld failure) Slipping, falling Seal Valves (3 - release, and two one way valves) Improper assembly/maintenance/fluid Further, some of these are slow, almost imperceptible failure modes. If the seal or a valve leaks slow enough that you don't notice, you might start work, not discovering until too late that the vehicle is lowering and finding yourself unable to extract your body from the slowly lowering vehicle. If you're lucky you can call for help. If not... If you have confidence that all of these are acceptable risks, then sure, for your definition of safe perhaps a hydraulic jack is "safe". I wouldn't trust my life with it, I wouldn't recommend it to any others, but if it's just you then not even the government can force you to employ better safety practices. Let's look at the jack stand failure modes: Structural failure (metal fatigue, pin/ratchet failure, weld failure) Slipping, falling There's simply not too much that's safer than a jack stand in terms of supporting a vehicle... except more jack stands. For me, though, this still isn't safe enough. One jack stand means one failure - thought perhaps unlikely - could result in injury or death. So at minimum I continue to use the hydraulic jack and a jack stand, but more often than not I'll use two jack stands for each lifting point and remove the hydraulic jack simply because it takes up so much room. What you really need to determine to answer your question is what is your level of acceptable risk, and what's the cost. If you experience a failure, what's the cost of the failure? Given that your life and limb are involved, the cost of failure is so high that, for me, the extra time and cost of setting up a jack stand is always worth it.
|
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51,610 |
In the picture below , I need to reattach two metal pieces located in the tailgate latch assembly on 2014 Ford Escape . The two metal pieces are located on middle right hand side of picture. The pieces are subject to pressure every time door is open and will get some jarring from door shutting and normal outside heat. Will epoxy do the job?
|
There is no such thing as "absolutely, perfectly, 100% safe." Each tool has its proper and improper uses, and each works either in parallel with other tools to increase safety and dependability, or in series with other tools ultimately reducing safety and reliability. Will a hydraulic jack hold up a car safely? That depends on the level of risk you're willing to take. In a hydraulic jack there are several failure modes: Structural failure (metal fatigue, fastener failure, weld failure) Slipping, falling Seal Valves (3 - release, and two one way valves) Improper assembly/maintenance/fluid Further, some of these are slow, almost imperceptible failure modes. If the seal or a valve leaks slow enough that you don't notice, you might start work, not discovering until too late that the vehicle is lowering and finding yourself unable to extract your body from the slowly lowering vehicle. If you're lucky you can call for help. If not... If you have confidence that all of these are acceptable risks, then sure, for your definition of safe perhaps a hydraulic jack is "safe". I wouldn't trust my life with it, I wouldn't recommend it to any others, but if it's just you then not even the government can force you to employ better safety practices. Let's look at the jack stand failure modes: Structural failure (metal fatigue, pin/ratchet failure, weld failure) Slipping, falling There's simply not too much that's safer than a jack stand in terms of supporting a vehicle... except more jack stands. For me, though, this still isn't safe enough. One jack stand means one failure - thought perhaps unlikely - could result in injury or death. So at minimum I continue to use the hydraulic jack and a jack stand, but more often than not I'll use two jack stands for each lifting point and remove the hydraulic jack simply because it takes up so much room. What you really need to determine to answer your question is what is your level of acceptable risk, and what's the cost. If you experience a failure, what's the cost of the failure? Given that your life and limb are involved, the cost of failure is so high that, for me, the extra time and cost of setting up a jack stand is always worth it.
|
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|
51,930 |
I've bought a car which has ugly label glued to its rear window. What are inexpensive and effective ways to remove it without residue? Edit : my car has it on the outside on the blank glass but it‘s good to know what to do when it is inside or on sensitive surfaces.
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The most effective thing I've found for this is heat. Warm the sticker with a hair dryer. When it gets warmed to a certain point it will easily pull away without leaving residue. One word of caution though, when it comes off the glass completely it will try to stick itself to your hand. Hot plastic is not something you want on your hand, so wear gloves and have some water ready to cool the plastic or a sooth a burn.
|
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|
51,950 |
In the Wikipedia PID list we can see that 0x0C for engine RPM, 0x0D vehicle speed, etc. Is this same for all car manufacturers? In Arduino examples we can see that data[2] reserves the PID (for engine RPM 0x0C ) and by converting hex to decimal data[3] and data[4] of the message and by the formula ((256*data[3])+data[4])/2 we can get the value of RPM. But when I try to apply this to a Citroën car, I can see 0x0C , but the data in the message does not change although the real RPM value changes. It means that this does not show RPM on that car. I am using PCan-View for reading the CAN bus. Does this affect the result? So can we say there are not general PID values? Thank you very much for your answers. Some parts of the data, which includes 0C, can be seen in below. 86) 91.6 Rx **0208** 8 18 **0C** 31 00 4C FF FF 27
99) 101.6 Rx 0208 8 18 **0C** 31 00 4C FF FF 27
107) 105.3 Rx **040D** 8 00 00 00 00 00 00 00 **0C**
114) 114.5 Rx **034D** 8 00 23 FA FA 00 **0C** 00 FF
735) 745.1 Rx 040D 8 00 00 00 00 00 00 00 **0C** These codes repeat many times during the data gathering. But row data is always the same, even when the car engine is running. If we consider address 034D has 0C in data[2], we have to calculate RPM with FA and 00 decimal values. But they never change. I am not sure that we are following the right path.
|
The most effective thing I've found for this is heat. Warm the sticker with a hair dryer. When it gets warmed to a certain point it will easily pull away without leaving residue. One word of caution though, when it comes off the glass completely it will try to stick itself to your hand. Hot plastic is not something you want on your hand, so wear gloves and have some water ready to cool the plastic or a sooth a burn.
|
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52,053 |
Most people know that for old or even somewhat old cars, manual transmissions are more efficient. Recently automatic cars have become almost as efficient or even as efficient as manuals. I was recently reading an article by Road & Track magazine that was comparing different sports cars, and it mentioned the fuel efficiencies of the manual versions versus the automatic versions, and actually listed the automatics as being more fuel efficient than manuals by about 2 mpg. Are automatic transmissions now really more efficient than manuals? Is this for all cars or just high-performance cars? If autos are now more fuel efficient than manuals then how have they managed to make this so?
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Traditionally... The major drawbacks of automatic transmissions were: parasitic losses in the torque converter, something which manual transmissions don't have. fewer gears, so a given engine was more likely to be in its sweet spot with a 5-speed manual than a 4-speed automatic during regular operation. gear selection logic which was inferior to well-trained human drivers Over time... Transmission manufacturers have worked out ways to reduce the impact of these drawbacks, including: Direct-drive to lock out the torque converter to prevent losses Adding more gears helps keep the engine in the right rev range for optimal fuel economy when the conditions allow for it ( 8-speeds are quite commonplace nowadays, even 10-speeds) Quicker and more intelligent gear-selection logic that can handle a wide variety of driving scenarios. For further reading: see this reddit comment , which does a good job of summarizing the answer to this question.
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52,859 |
During winter here in Canada, my 2011 Cruze seems like it has humidity on the inside of the windshields. When I take a look at other cars besides mine, there is moisture on the exterior, not interior. Could I have a sealing problem on some joints on windows and windshields? It's really annoying when the temperature changes suddenly creating a layer of thin ice like dust made with ice, inside. What can I do about this?
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There is something (very) wet inside your car. Feel around the floor, look at all the lowest points of the floor. If the front passenger floor is wet check the hoses to the heater core. Check all window gaskets. Check the spare tire well and the trunk gaskets. Check to make sure that all windows roll up completely. A fold or tear in a gasket or debris can make it look like the window is closed when it's not. How long has this been going on?
Has your car been in an accident?
Is your car always parked outdoors? Sources for water are the cooling system and water from the external environment. There is water inside your car, you just need to find it and then figure out how it's getting in.
|
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54,202 |
I just had to put a doughnut on my car and I used the typical manufacturer car jack that fits into that little slot of metal near your wheel. After I got all the lug nuts out, I tried pulling the wheel off in several different ways with all my strength and it was still stuck, so I went under the car and kicked off the tire and it fell to the ground. I wouldn't think this is a safety issue because you got a ton of weight sturdily mounted onto the jack, but I really hate those jacks that you have to crank with your hand that seems to come with all cars. I want to get one of those jacks that you can pump and release, jacking your car with one of those is really easy and takes like 10 seconds or less. Do I have anything to be concerned with here if I go this route? Being crushed by a car is not how I want to spend my future!
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The ONLY time you should crawl under a car is when it is supported by a jack stand or on a lift. A jack is used to jack the car up and let it down. It is a huge safety concern to use it to support the car while crawling under it. You can kick the tire from the outside of the car if it won't come off, but keep your body parts away from underneath the car. When a jack lets go it does it in a hurry, without notice, and without provocation. Use it only to temporarily suspend the vehicle when needed, but nothing else. EDIT: As a commenter pointed out, differentiating between a "jack" and a "jack stand" may be beneficial to the uninitiated. To that end, here are some pics and explanation. Scissor Jack Typical scissor jack which is used on a lot of vehicles as OEM equipment from the factory. While scissor jacks vary in size and shape, it should be noticed the small base and head, which do not lend well to stability. They are small so they can be stored in a small space. Other jack types may be used as an OEM for changing tires in an emergency, but they will almost always be small and overall have stability issues. This should not be used to keep the vehicle supported, but rather for lifting and lower the vehicle. Jack Stand Typical jack stand which is used to support vehicles for a more lengthy amount of time and where safety is a concern. Jack stands will vary in size, shape, and amount they can support, they will almost always have a wide base to make them stable while supporting a vehicle. This doesn't make them perfect, but when used properly, there should be no fear while crawling under a vehicle. Notice, the positive locking support near the head which allows for height adjustablility. As long as this is locked into place correctly, there is very little to fear about failure during use.
|
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54,209 |
Recently I have noticed that the air from ac vents sometimes cold, but sometime less cool/fan mode for a while, before return to cold.
I also noticed almost continuous "hissing" sound from around the place where cabin filter is located.
I checked the low pressure when AC is on max, it shows 32 PSI on ambient temp of 33C (91F) at 48% humidity. Refrigerant is R134a. I have visited repair shop once, and they suspect the selenoid valve in ac compressor gets dirty, so they cleaned it. But I could feel the problem persist, but it does feel better, (the "fan mode" get shorter). They said, the clutch is engaging when its not cold, so its not a clutch or belt issue. I wonder if is it caused by not enough refrigerant? Note : When AC is off, the low pressure is 80 PSI. Thanks!
|
The ONLY time you should crawl under a car is when it is supported by a jack stand or on a lift. A jack is used to jack the car up and let it down. It is a huge safety concern to use it to support the car while crawling under it. You can kick the tire from the outside of the car if it won't come off, but keep your body parts away from underneath the car. When a jack lets go it does it in a hurry, without notice, and without provocation. Use it only to temporarily suspend the vehicle when needed, but nothing else. EDIT: As a commenter pointed out, differentiating between a "jack" and a "jack stand" may be beneficial to the uninitiated. To that end, here are some pics and explanation. Scissor Jack Typical scissor jack which is used on a lot of vehicles as OEM equipment from the factory. While scissor jacks vary in size and shape, it should be noticed the small base and head, which do not lend well to stability. They are small so they can be stored in a small space. Other jack types may be used as an OEM for changing tires in an emergency, but they will almost always be small and overall have stability issues. This should not be used to keep the vehicle supported, but rather for lifting and lower the vehicle. Jack Stand Typical jack stand which is used to support vehicles for a more lengthy amount of time and where safety is a concern. Jack stands will vary in size, shape, and amount they can support, they will almost always have a wide base to make them stable while supporting a vehicle. This doesn't make them perfect, but when used properly, there should be no fear while crawling under a vehicle. Notice, the positive locking support near the head which allows for height adjustablility. As long as this is locked into place correctly, there is very little to fear about failure during use.
|
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55,689 |
My car has an O/D button under the transmission button. When I press it, it turns O/D off. When O/D is off, the revs go up more than when O/D is on. What does O/D mean and what does it do to the car? I assume whatever O/D is, it's on by default when I start the car?
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The "OD" means over drive. It's the last gear in your transmission. When the indicator shows as "off", it means the transmission won't go into that gear. Overdrive provides a mechanical advantage for the engine to run at a slower speed when traveling at highway speeds. This allows for better fuel economy. As I stated, it is the last gear in the transmission and provides a better than 1:1 ratio. Depending on the car, it will be around .70:1 (or thereabouts). As far as whether it's on/off by default, you should allow the vehicle to achieve O/D whenever it wants to, which will allow the best fuel economy. It appears the button on your shifter is actually a switch. If you push it, it changes position and therefore the function it will allow. Since it does this, there's no real "default". If it were just a push button and the computer decides your actions, then there would be a default setting. Like I said, leave O/D on to operate normally. Modern vehicle computers are smart enough to know when to use O/D and when not to.
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55,694 |
I have a 2008 CRV and recently the air conditioning stopped working I have already tried replacing the relay thinking that might’ve been it when I turn the air-conditioning on I can hear something kick in and the idle of the car goes down so it seems like the air-conditioning compressor is turning on however the air coming out of the van never gets cold. Unfortunately the car has over 100,000 miles on it and I know that there have been recalls on the air-conditioning compressors. As a next step what can I do to try and diagnose the problem I was thinking perhaps I would try adding refrigerant but it seems strange to me that the air conditioning would just stop working all the sudden if refrigerant where the issue. Is there any harm in getting a can of refrigerant and a hose and trying it out other than the fact that I’ll be spending around 30 or $40?
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The "OD" means over drive. It's the last gear in your transmission. When the indicator shows as "off", it means the transmission won't go into that gear. Overdrive provides a mechanical advantage for the engine to run at a slower speed when traveling at highway speeds. This allows for better fuel economy. As I stated, it is the last gear in the transmission and provides a better than 1:1 ratio. Depending on the car, it will be around .70:1 (or thereabouts). As far as whether it's on/off by default, you should allow the vehicle to achieve O/D whenever it wants to, which will allow the best fuel economy. It appears the button on your shifter is actually a switch. If you push it, it changes position and therefore the function it will allow. Since it does this, there's no real "default". If it were just a push button and the computer decides your actions, then there would be a default setting. Like I said, leave O/D on to operate normally. Modern vehicle computers are smart enough to know when to use O/D and when not to.
|
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|
57,143 |
I had an engine seizure that happened while I was driving the car: it ran low on oil and suddenly the engine stopped working (with a bit of smoke). Now after being towed, I have left the car (and added oil) for a couple of weeks, hoping to try and free up the engine. I read online that you can only un-seize an engine if it's caused by long periods of inactivity. Apparently a seizure while-in-use is the most difficult to fix and costs the most. I'm pretty close to accepting my loss here, however I need some reassurance (or closure) before I make this final decision. Should I choose to try and fix it, I'm going to need to get a few lubricants and to recharge the battery (which died while I was trying to restart by the roadside). For the record it's a 2008 Toyota Yaris, 1.0 liter engine (1KR-FE).
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A seized engine due to not being used is usually due to the pistons / rings sticking in the bore, which with some freeing fluid may be easily solved, but this will not help the future life of the engine. An engine seized due to lack of lubrication, such as you describe, means that the crankshaft bearings, main bearings and camshaft bearings have all probably seized - seizing in this situation means serious surface damage to the bearing surfaces in contact - in fact the surfaces can actually get welded together. Just adding fresh oil will not solve the problem - this damage will need an engine re-build.
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|
57,461 |
A neighbor friend of mine offered to change my brakes on my Pontiac Torrent, well my husband had the proper tool to remove the lug nuts off my car in his truck, and the neighbor along with some other helpful bystanders took it upon themselves to crank, strip, smash, hammer, melt tweak and literally beat the absolute hell out of one of my lug nuts. My husband came home and popped off all the other lug nuts with ease because he had the proper tool. But the final one that had been damaged beyond recognition is still on. My vehicle is completely undriveable as well as one side has brakes and the side that the lug nut is stuck on doesn’t. So I can’t even drive it to a mechanic! My lug nut has been chiseled, hammered, torched, and drilled and it’s still not going anywhere. What else can I do? It’s been a week since this fiasco started.
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The first thing I'd establish is to work out if the hub can be removed from the car with the wheel still attached. I encountered a similar scenario some years ago working on a car with locking wheel lugs and no key. I was able to remove the hub cap, dust cover and large castle bolt which allowed me to put the wheel and hub assembly on the bench. Doing this may also mean you can drill the wheels stud out from the back which may be easier. Failing that, I'd order a "locking wheel nut removal kit" which is essentially a selection of sockets with a reverse thread in them so as you turn it in the direction required to unscrew the lug nut, it tightens itself onto the nut until it binds at which point the nut begins to unscrew. Another option to try is finding a sacrificial deep or semi-deep socket that is an interference fit for the nut then welding through the centre of the socket onto the lug nut. You can then turn it off normally. It may be worth calling your local auto shop. Yes, you can't drive it to them but some may be happy to come to you with a selection of tools or recover it to their shop on a tow truck or trailer. Good luck, it's an awful pickle to be in.
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|
57,738 |
My bicycle tires go to 60 psi, and I can easily fill them up from nothing with less than 10 pumps. My car tires are at 32 psi, so shouldn't they be even easier? Yet I have never heard of anyone hand pumping their car tires. Why not?
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People do that. Sometimes, at least. I have a high quality (high volume) bike pump at home, and occasionally I use it to check the pressure on the car, or to top off if it's obviously missing something. I find it 100% hassle free and not in the least problematic. But then I have a really good volume on that pump; also I can use my whole body to pump (the type where you stand on the "foot" of the pump and can pull/push the handle by using your full upper body weight/strength). I would probably hate it if I only had my secondary "trail" pump, which rests in my bike backpack all the time. First of all, I probably could not even fit it to the car tire, as it has no separate tube, and secondly it would really be a huge amount of work to get all that volume in. Besides, the not so technically inclined person might not even be aware that it is technically possible to do so (not every pump fits the car valves), and people may not be aware that bikes have higher pressure than cars anyways (well, they may be aware, but subjectively a bike tire looks so small and flimsy in comparison to a huge car tire... with a car on top of it ;) ).
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