To make a long story medium-sized, I've created this thread from the question that I and my auto shop teacher tried to find the answer to. That question happened to be about the existence of the EGR valve in a Nissan 350z. After combing the Internet (for too long), I found that its CVTCS (their kind of variable valve timing) was responsible for taking enough of the exhaust gasses back into the cylinder, reducing emissions like nitrogen oxides and blah blah blah... Since I took too long to find and comprehend that answer, I didn't finish the rest of my homework in time for piano practice and my mother freaked out on me, like most stereotypical Asian parents. It was interesting to know that bit of info though.

This thread is meant to educate anyone who has a question reguarding cars, motorcycles, their engines, and so on. If someone asks a question and you know the answer, then answer it as best as you can. If you think someone's answer is wrong, do the people who really want to learn a favor and don't flame, praise the answerer's stupidity sarcastically, moan, or be an asshat. It is a complete waste of space, time, knowledge, brain matter, physical energy, and mental effort to flame person after person because he/she answered the question wrong or make himself/herself look like the most educated person about everything. More importantly, it's a waste of knowledge because I would hate to see this thread go if someone decides to bring along lighter fluid and some lighters to watch this thread die. I might even have to kill it myself (with the help of a mod of course).

That doesn't mean that everyone will follow the above so answerers, be careful about your answer to prevent this from happening. Make them as complete and precise as you possibly can. Most importantly, put a good amount of effort into it and you'll be fine.

I do not care if you're a tuner who wants to find how how to modify your car in any way, a racer looking for serious advice, a hybrid of both, or some crazy inventor. If a person wants to learn, teach him/her, not douse him/her in alcohol and throw a cake with a candle on it. If you do not like the question or the person who is asking it, don't post your negativity here, not even sarcastically or in such a clever way that the answerer can't decipher it's meaning.

I do care if the answer you are looking for is life-threatening or dangerous, like dealing with battery acid so answerers, refrain from answering, offer an alternative, or suggest safety precautions. Suggestions that could possibly cause damage to property (either belonging to you or someone else), physical harm, and law breaking (because we all live in different places) are to be followed at your own risk. You have all the responsibility to make the decision on whether or not to follow the suggestion, so you are also responsible for the outcome of following the suggestion.

Try not to stray off topic, this will make answers hard to find. Remember, this is for automotives, not nescesarily for computers or advanced quantum physics (whatever that is).

If you have an answer, try to quote or mention the name of the person you are giving the answer to. That makes it much easier to find.

Lastly, don't be afraid to ask. We all started learning from basic ideas and it's ok if you don't remember or know them, just as long as you know them by heart later on. Sure the answer may be in Google but maybe the answer is incomplete, far too complex to comprehend, or you're fresh out of time and want to find the answer as soon as you come back (hopefully).


I'll start off first: I do know that a stiffer set of springs and dampeners means less grip when taking on bumps since the tires can go airborne. But what if you had a flat surface and decided to take a turn? Given that everything is the same except for spring stiffness, dampener setting, or both, would the car have less traction on the wheels where these settings have been applied? I was thinking that it would have more since the tyres are forced into the ground but sims as well as engineers say no. Why? (remember, I'm in 10th grade so don't go into extremely complex math or similar things)

Springs won't force the tyres into the ground, as they can only apply the force that is applied to them - i.e. the weight of the car.

Stiffer springs will:

• raise the ride height of the car unless the springs are shorter or the spring platforms are moved (not usually adjustable on a standard road car).
  
• Reduce squat, dive and compression when accelerating, braking and going through dips etc.
  
• Reduce body roll (not always a good thing as it depends on the specific suspension geometry)
  
• Increase the responsiveness of the chassis - load transfer would be quicker, and so a car would turn in well
  

All the above assume that the ratio of front:rear stiffness remains the same. If not you will cause an over/understeer situation in the chassis.


Dampers are a lot more complicated, but essentially it comes down to how quickly they let a car move on its springs, be it from bumps or accelerative/cornering forces. A softer damper will allow more movement before the spring is damped, which will result in the car feeling a bit spongey, and response times falling, even to the point of uncontrolled oscillation. Excessive damping would (for the purposes of this simple post) make the spring act like it was solid, giving great response on a totally smooth circuit, but being rubbish at bumps or when actually cornering.

The whole thing comes down to a set of compromises. A road car will tend to have a softer setup to absorb bumps and reduce response (the so called sneeze factor - can the driver sneeze safely without the resultant jurk causing him to end up in a hedge backwards?), with damping to maintain comfort rather than response or traction and without oscillations after a bump.

A race car will be much much stiffer on the basis that tracks are smooth (even the 'bumpy' ones), and drivers tend to concentrate a bit more (and/or be a bit more talented).

A road car could typically be stiffened by about 10% - 15% before it becomes too much for public roads, although of course the final figure depends on what you want to achieve and how much money you are prepared to put into dampers. However, this is often much better than lowering a car, which is unlikely to do much good for suspension geometry. Lowering and stiffening is asking for trouble, as an extra short, stiffer spring probably won't be able to cope with public road surfaces, especially once you start driving quickly.

I hope this answers some of your questions. As always this is very simplified, so use it as a general text rather than the advice needed to tune a car. Many people (who I consider morons) are happy to buy a set of springs and dampers for their car at a cost of £80 per corner. Some even avoid accidents afterwards. At the end of the day you have to make the decisions about your car, and whether or not you use common sense and/or careful analysis is up to you.

Nice idea this thread.
Can someone explain the terms "bridgeport" and "Allmotor" to me?

Allmotor usually refers a totally normally aspirated engine. The engine is then said to be all motor, rather than assisted by supercharging or nitrous etc.

Bridgeport is when an cylinder's valve port is shared between multiple valves or cylinders in the inlet or exhaust (usually inlet) manifold.

Thanks Tristan. That helped clear some things up.

Quote from tristancliffe :

All the above assume that the ratio of front:rear stiffness remains the same. If not you will cause an over/understeer situation in the chassis.

That part caught my eye. What causes this oversteer/understeer to happen when you change the stiffness ratio between the front and rear and how does it work?

Good thread, this is more fixing an issue than finding out how a motor works.

For whatever reason the back wheels, assumed to be the brakes in my parents car (Vauxhall Omega Auto) has developed a squeak, the car has been taken to the garage several times about it and told there is nothing wrong with the brakes, despite this the squeak is getting louder, although when they cleaned the discs and pads the squeaking stopped for a weekish. After intarwebbing it for a few hours all I got was the squeak is caused by microscopic bends in the discs caused by sitting at the lights with the foot brake on. Which means noise that would normally be inaudible is now resonating off the discs.

Is this the only reason for the squeak and if so is there an easy and/or cheap fix for this, or is it a case of getting the discs changed?

What causes flames coming out of the exhausts of certain cars, especially racing cars?

Ooh! Ooh! I know! I asked this last week

Quote from tristancliffe :

Race engines run a lot of overlap (inlet and exhaust valves open at the same time near top dead centre on the inlet/exhaust strokes), and tend to maintain fuelling on the overrun (off the gas) to keep exhaust gas temperatures and valve/cylinder temperatures under control (and because it improves pick-up a bit too). The fuel can go straight in the inlet valve and straight out of the exhaust valve, where the temperatures can be enough to ignite the fuel and cause pops and flames.

Ideally you don't really want it, if only because the shock waves aren't great for exhaust longevity, but some people reckon the gains are worth the costs. I tend towards no popping and coughing if I can help it, but sometimes throttle response degrades too far (in a track environment - you'd never EVER notice it on the roads) to get rid of it completely.

i want to know something. how does smoke come off the tires when spun?

Quote from Scatter :

That part caught my eye. What causes this oversteer/understeer to happen when you change the stiffness ratio between the front and rear and how does it work?

Stiff rear springs mean during cornering it won't get as much traction, and under acceleration during cornering you wont get traction due to the fact that the power cant get down because theres no weight transition, as its all on the front.

Same with softer springs in the front, turn in and brake and it'll all dip down to the front, and will understeer.

Quote from Lateralus :

What causes flames coming out of the exhausts of certain cars, especially racing cars?

Most race cars use straight through exhaust system, no cat, no mufflers etc.
Most of the time, unburnt fuel is caught by the cat or the muffler, if this doesnt happen it can ignite in the exhaust and pop flames.

Usually only happens with a rather rich mixture, however.





If anyone wants to correct my info, feel free
this is just from my understanding

Quote from Exile R :

i want to know something. how does smoke come off the tires when spun?

Well, when there's smoke, there's probably fire (not really). I think the friction caused from spinning the tires causes it to heat up so much that it starts a chemical reaction, thus, you get smoke. I also heard that it is bad for the tire because once the tire cools down, it hardens and loses its grip because of the chemical reaction. That's only a guess though so I could be very wrong.

Quote from Klutch :

Same with softer springs in the front, turn in and brake and it'll all dip down to the front, and will understeer.

I thought it was the other way around? Softer springs in the front causes the chassis to dive toward the front, giving them more grip? That's how I thought of it in LFS.

I just realized that I forgot about weight transfer! Maybe that's what causes the phenomenon of oversteer/understeer with the spring settings. Can someone clarify weight transfer for me? Or whatever else causes understeer/oversteer with a different front to back ratio of spring stiffness?

Quote from Scatter :

I thought it was the other way around? Softer springs in the front causes the chassis to dive toward the front, giving them more grip? That's how I thought of it in LFS.

I just realized that I forgot about weight transfer! Maybe that's what causes the phenomenon of oversteer/understeer with the spring settings. Can someone clarify weight transfer for me? Or whatever else causes understeer/oversteer with a different front to back ratio of spring stiffness?

It depends how soft the springs actually are.

If the springs are really soft, you brake and turn in, youll instantly get understeer. At the same time, if its very hard you'll brake and wont get any traction when turning due to the fact that theres no weight on the front.

Weight transfer comes into play under braking, cornering, and acceleration.
You brake, the front end will usually dip down, you turn, it'll have body roll, then as you accelerate all the weight goes to the back and adds traction out of the corner.

Depending on what spring combination you have, each of those will be effected.

Hard:
Brake, it'll have no weight transfer if its super hard, and the turn in will be crap and will under steer

Exit the corner, step on throttle, no weight transition to back, so the tyres either just spin, or you take LONGER to get to full throttle.

Bodyroll, mid corner..if you step on the throttle itll probably step out on you and cause over steer

Softer is pretty much the opposite of that



as i said, feel free to correct me if im wrong, always got time to learn more ^_^

Quote from Exile R :

i want to know something. how does smoke come off the tires when spun?

Really? I have feeling that question is a bit sarcastic, but on the off chance that it isn't..

It's friction with the road. Try rubbing your hand on your arm really quickly for a few seconds and you'll find it gets very hot. If you do that with a tyre and a road, with the weight of a car pushing down, the heat is enough to burn the surface of the tyre off, resulting in smoke.

Quote from Scatter :

That part caught my eye. What causes this oversteer/understeer to happen when you change the stiffness ratio between the front and rear and how does it work?

Tyres behave in a funny way. Two tyres with 100kg each will develop more grip than one tyre with 200kg load. This is called 'load sensitivity', and basically means that load transfer (the weight moving to the outside tyres) is a bad thing!
The amount of load transfer is merely a function of the height of the CoG and the track or wheelbase (depending on lateral or longitudinal acceleration), but the distribution of the load transfer across the front or rear axles is defined by it's stiffness (a combination of spring and roll bar usually).
An infinitely stiff front (with a soft rear) will do ALL the weight transfer, so the tyres at that end will be as unevenly loaded as possible. As one tyre develops less grip than two sharing the same load, so the front end loses grip and understeer develops. Infinitely stiff rear = oversteer for the same reason.
A good handling car might have a 40:60 stiffness ratio (it's often quite close to the static weight distribution of the car, but only as a rule of thumb), and stiffening the car so that that ratio changes will change the handling of the car.

Hoep that helps....

Quote from P5YcHoM4N :

Good thread, this is more fixing an issue than finding out how a motor works.

For whatever reason the back wheels, assumed to be the brakes in my parents car (Vauxhall Omega Auto) has developed a squeak, the car has been taken to the garage several times about it and told there is nothing wrong with the brakes, despite this the squeak is getting louder, although when they cleaned the discs and pads the squeaking stopped for a weekish. After intarwebbing it for a few hours all I got was the squeak is caused by microscopic bends in the discs caused by sitting at the lights with the foot brake on. Which means noise that would normally be inaudible is now resonating off the discs.

Is this the only reason for the squeak and if so is there an easy and/or cheap fix for this, or is it a case of getting the discs changed?

A good way would be to put a second groove on the PADS at 90° to the existing groove. Just using a hacksaw would be enough (but be careful, and don't go too deep, especially during the trial period!), and help allow the dust to escape.

Brake squeal is most often caused by a build up of dust that can't escape. A second groove will give it somewhere to go.

Quote from Lateralus :

What causes flames coming out of the exhausts of certain cars, especially racing cars?

Quote from Crashgate3 :

Ooh! Ooh! I know! I asked this last week

Thanks crashgate, saves me typing again!

Quote from Exile R :

i want to know something. how does smoke come off the tires when spun?

The friction heats the tyre and causes the rubber to react (oxidise), and that releases smoke. On a damp day it's very likely the smoke is actually steam.

Quote from Klutch :

Stiff rear springs mean during cornering it won't get as much traction, and under acceleration during cornering you wont get traction due to the fact that the power cant get down because theres no weight transition, as its all on the front.

Same with softer springs in the front, turn in and brake and it'll all dip down to the front, and will understeer.

True, but once you allow chassis movement to get in the analysis it becomes a whole lot more complicated! But you don't want weight transisiton (although you have to have some), so good traction on corner exit will be when the tyres are as evenly loaded as possible, which is why cars with good traction tend to have understeer most of the rest of the time, to keep the load transfer at the rear to a minimum.

Quote from Scatter :

I thought it was the other way around? Softer springs in the front causes the chassis to dive toward the front, giving them more grip? That's how I thought of it in LFS.

Try and ignore chassis movement, because that causes all sort of problem - geometry changes, CoG movement, camber change, and quite quickly you'll need a supercomputer to work it all out! Softer springs do allow a chassis to move more, but at the same time they'll reduce the lateral load transfer at that end, which gives it more grip.

Quote from Scatter :

I just realized that I forgot about weight transfer! Maybe that's what causes the phenomenon of oversteer/understeer with the spring settings. Can someone clarify weight transfer for me? Or whatever else causes understeer/oversteer with a different front to back ratio of spring stiffness?

I think I did further up there, but if it's not clear I'll have another go. I'm no chassis dynamics expert at all. I only know the basics as part of being my own race engineer.

Quote from Klutch :

It depends how soft the springs actually are.

If the springs are really soft, you brake and turn in, youll instantly get understeer. At the same time, if its very hard you'll brake and wont get any traction when turning due to the fact that theres no weight on the front.

This is more likely caused by the car being so soft that the camber control goes out of the window will too much roll - the car is said to 'fall over' and not grip. Again, allowing chassis movement to come into the thought process makes it all a LOT harder to understand. By all means try, but don't let the movement trick into think it's doing much!

Quote from Klutch :

Weight transfer comes into play under braking, cornering, and acceleration.

correct!

Quote from Klutch :

You brake, the front end will usually dip down, you turn, it'll have body roll, then as you accelerate all the weight goes to the back and adds traction out of the corner.

hmmmm

Quote from Klutch :

Hard:
Brake, it'll have no weight transfer if its super hard, and the turn in will be crap and will under steer

Nope, it'll have MORE load transfer if it's stiff. That causes the understeer. Load transfer is bad, and should be minimised with low CoGs, wide tracks and not too much stiffness but enough to control camber and aero (in the case of aero a super super stiff platform might be better, but it'll hurt mechanical grip).

Quote from Klutch :

Exit the corner, step on throttle, no weight transition to back, so the tyres either just spin, or you take LONGER to get to full throttle.

MORE load transfer causes less rear grip. Whether or not the wheels (inside or both) spin is getting into the world of diffs and driver skill!

Quote from Crashgate3 :

Really? I have feeling that question is a bit sarcastic, but on the off chance that it isn't..

It's friction with the road. Try rubbing your hand on your arm really quickly for a few seconds and you'll find it gets very hot. If you do that with a tyre and a road, with the weight of a car pushing down, the heat is enough to burn the surface of the tyre off, resulting in smoke.

Essentially that is spot on. I'm sure the actual process is a bit more complicated, but I'd be more than happy with that description when it comes to exam time.


I did mention the annual "Miscellaneous Automotive Questions Thread Exam" didn't I?

I'll have a shiny apple for you tomorrow morning, Tristan

On the subject of exams, I reckon this thread should come with a disclaimer, because if you give someone advice and they follow it, you are liable if anything goes wrong and something breaks or someone gets hurt.
Something like "following any advice given in this thread is done entirely at your own risk and the posters accept no responsibility for any accidents that may occur" would cover it.

And while I'm here I might as well ask - is there any cheap way of squeezing a little extra power out of a car without having to inform the DVLA or insurance company? Will something like "performance" spark plugs or other stuff of the like, really do much (since I know piss all about engines)?

Indeed, all the posts, questions and replies MUST carry the disclaimer that anything should be checked with a trusted professional before putting it into practice, and none of us can be held responsible for harm or damage to properly or persons howsoever caused.

Dajmin - in a word, no. The benefits of sporty spark plugs are more likely to be emissions and placebo - you know you've got sporty spark plugs, so therefore it must feel quicker. Magnets on fuel lines don't work. Resistors from eBay at 99p don't help. Using a decent quality fuel - Optimax, BP Ultimate, Tesco99 (still not sure about this, but has biofuel in it, which has a higher calorific value, but can also be blamed for rising food prices) - has much more potential for giving you a few extra horses, but results vary on an almost individual basis. I've measured the difference in 0-60 in my car before and after, and I get more miles to a tank of fuel on Optimax (or V-Power if you prefer the stupid name).

Or save your money on trinkets and go on a race driver training day and learn to use what power you've got 20% more effectively!

In a few different Best Motoring International videos I've heard the drivers mention some cars have "crossed transmissions". What does this actually mean?

Hmmmm, not 100% sure on this, so I did a tiny bit of research (1 minutes worth).

Found this thread : http://www.superhonda.com/foru ... sed-tramsmissions-201378/
Which pointed me to : http://science.howstuffworks.com/gear3.htm

And that gives the impression that a crossed transmission is one that has a gear (or set of gears) to transfer drive through 90°, probably for packaging reasons. Don't some Ferraris have the gearbox 'underneath' the engine, with the crankshaft torque transferred down via a pair of 90° helical gears?

Sorry, that's the best I can do.

Thanks for clearing a few things up, but i now have a question of my own.

I've recently acquiered and un registered, defected(cant be licensed) vehicle for free with my brother.

We don't know if it runs, we had the idea of hot wiring it...but then we saw the imoboliser, so itll be more tricky than i thought...

When getting it onto the tow truck, the steering lock had been disabled, so you could turn it without the car ignition being on. However, im not sure as to how it was dis engaged...

As we took the car in, and out of the car garage today, as we were tearing at the inside removing a few things, it was getting late and we decided to leave it for the night. So we went to push it back into the garage and what do you know...we turn about 2 degrees and the steering lock re engages, so now its stuck on the driveway...

Curious as to how to remove the steering lock, if anyone knows?

slide hammer.

Quote from Becky Rose :

slide hammer.

Not really a fan of taking hammers to a car :P

Let alone a steering column =/

One way would be a long tube (scaffold tubing is great), and slide it over the lock, then lever down until it breaks the lock off.

If you want to be a bit nicer, you can drill out the shear bolts that hold the lock onto the column (the bolts that don't appear to have heads), and the whole thing will come off.

Then you can dismantle the lock assembly to remove the steering lock itself, and hey presto a mobile car!

Quote from tristancliffe :

Hmmmm, not 100% sure on this, so I did a tiny bit of research (1 minutes worth).

Found this thread : http://www.superhonda.com/foru ... sed-tramsmissions-201378/
Which pointed me to : http://science.howstuffworks.com/gear3.htm

And that gives the impression that a crossed transmission is one that has a gear (or set of gears) to transfer drive through 90°, probably for packaging reasons. Don't some Ferraris have the gearbox 'underneath' the engine, with the crankshaft torque transferred down via a pair of 90° helical gears?

Sorry, that's the best I can do.

Yeah, I've seen those types of forum posts before but they don't sound very authoritative. The how stuff works explanation seems reasonable though, thanks.

My turn for a question (and it is automotive related!)

I've gone and broken a 6mm tap off in a thread, quite some way beneath the surface. A colleague had a very old set of tap extractors, but they're knackered. Short of getting a set of extractors tomorrow, does anyone know of a way of getting one out? It's 4 flute if that makes any difference.

Can't weld, as it's in a fibre reinforced panel.
Can't drill as it's gonna be very hard material
I tried use a pair of long, thin needle nose pliers to twist it out, but that didn't do the pliers much good (fixed them though )

I'm stuck, and I really want to get it [the tap you dirty buggers!] out tonight!

Edit: Are masonry drills hard enough to drill a tap out so I can break it up? I've got a set of small ones that might work, but don't really want to knacker them needlessly!