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02-12-2008, 05:23 AM | #31 | ||
Master Connector
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Re: Whats the point of Front Wheel drive?
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And that maybe your problem. Is it the engineering that is letting the idea of FWD performance down, or our failure to reconcile your understanding of the engineering with our real world experiance? As has been said several times, there are a variety of very quick, very fun to drive, FWD performance cars. Made by companies with an understanding of automotive engineering that far away exceeds the knowledge of anyone on this forum. Try and look at it a different way. Motor bikes go very quickly on two wheels. If you watch a fully race prepped FWD, driven properly on a circuit, they tend to do the same thing. It's just the wheels are laid out differently, and there are an extra set hanging out the back that stop it tipping over backwards under acceleration.
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02-12-2008, 05:52 AM | #32 | |||||
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Re: Whats the point of Front Wheel drive?
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I have had a similar discussion on another board. Fortunately, I had the good sense to just quote out of a reliable book rather than try to explain the things myself. I'm going to quote myself from that forum right now: Quote:
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02-12-2008, 08:37 AM | #33 | ||
The Red Baron
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Re: Whats the point of Front Wheel drive?
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Can be found for around $500, has a five speed Getrag, and has a very good suspension for the time. Can run 12s reliably for very cheap. Can be found with t-tops. Port fuel injection. I'm not sure of insurance, but it should be in the same range. You can find replacement parts anywhere. No automated crap |
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02-12-2008, 08:56 AM | #34 | ||
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Re: Whats the point of Front Wheel drive?
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we have a winner. and guess what? i actually really wanted one of those before i got my camaro it was as simple as, i couldnt find one. also, body build-quality is an issue too. my camaro is rust free whats funny is that from the right angles, they even look pretty similar the daytona even has the "camaro" rear taillight triangles... (if you havent noticed, when viewed from the side, the rear tailights form a triangle-esque shape http://www.moparautos.com/images/84day2.jpg |
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02-12-2008, 01:44 PM | #35 | ||||
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Re: Whats the point of Front Wheel drive?
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The drive traction you are soo concerned about is only an issue in two situations. One is traffic light racing, the other is the 1/4 mile drags. In all forms of racing other than stupid straight lines it is not an issue. Quote:
See the problem with your theory is that it hasn't been tested. The outlier at this stage is your lack of knowledge about the very vehicles you're discussing. Quote:
Like the stopping distance of a mazda 3 (fwd) vs an RX8 (rwd). Oh look at that, the mazda 3 stops better in the wet. http://www.rx8.co.nz/Reviews/pr_brake_2904.aspx Take a look here and you'll see many fwd cars pulling up faster than the rx8 too. http://www.movit.de/rahmen/stoptbl.htm |
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02-12-2008, 04:24 PM | #36 | |||
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Re: Whats the point of Front Wheel drive?
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uh huh i guess i see your point even though your camaro isnt 500 bucks anymore, and when it was, didnt run anywhere close to 12s. another car that fits your model? a foxbody crustang(wait, no ttops. why is this a big deal?). or a mkIII turbo supra, or a z31 turbo 300zx, or a swapped rx7, or a turbo 240sx(wait no ttops again. just me but ttops isnt all that.), how about such make believe cars as a volvo 240 wagon with a 5 liter bmw v12 in it? irocs get bad gas mileage, handle like shit, dont look good in my opinion, and have technology straight out of 1971(except for the fuel injection). theres cars that can do things your camaro never could. have you ever driven other stuff? ive been at the helm of a camaro with a turbo 3.8 and took it up to 150mph on the freeway, and tried to get it to turn on twisty roads. my old sentra could handle more confidently.
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02-12-2008, 07:02 PM | #37 | ||||
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Re: Whats the point of Front Wheel drive?
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Drive traction is an issue any time you can spin the wheels. If you are a professional racer, or someone racing a higher end car, it matters a lot of the time. If you are someone racing a small, FWD economy car, or any car without much grunt, not so much. Quote:
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02-12-2008, 07:07 PM | #38 | |
That thing got a Hemi?
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Re: Whats the point of Front Wheel drive?
This is now lapsing into little attcks against each other.
i'll put this simply: if you can't put your point across without being whiny and bitchy, and can't accept each others' points of view, regardless of right/wrong i will close this thread. this applies to everyone.
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02-12-2008, 07:08 PM | #39 | ||
The Red Baron
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Re: Whats the point of Front Wheel drive?
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02-12-2008, 07:15 PM | #40 | |||
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Re: Whats the point of Front Wheel drive?
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Again with reference to weight distribution. You need some data, not hand waving of what you think the weight distribution is. It might help you understand why an audi A3 can stop harder than an RX8. Quote:
I am an engineer, I am familiar with eng-tips.com and I don't think the engineers there would agree with your blanket statements on the handling of vehicles you admit to not having driven. |
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02-12-2008, 07:51 PM | #41 | |||||
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Re: Whats the point of Front Wheel drive?
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When one side of this sway bar hits a bump, the other wheel gets pulled up as well, decreasing traction even on the previously unaffected side. You are ruining part of the benefits you used to get from independent suspension. Yes if you had a soft sway bar this wouldn't be such a concern, but when you ask a swaybar to fix poor weight distribution and suspension geometry that isn't helping, you may not be able to make it soft. Quote:
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Anyway, I have quoted a large exerpt and I don't think it needs more context (it's certainly not worth typing out the pages either side of it). What you take from it is up to you, I have been pointing people to it because I don't think there is much else you can take from it. Quote:
For the record, I have driven my fair share of FWD cars, but not in a performance situation. Even if I had, I can hardly trust the seat-of-the-pants measurements I would have come up with. |
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02-12-2008, 08:39 PM | #42 | ||
The Red Baron
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Re: Whats the point of Front Wheel drive?
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Also, I do agree with you about limits to FWD. You really don't want to go much past 350 hp or you're asking for potentially asking for traction issues, shearing axles, and blowing up CV joints. |
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02-12-2008, 08:54 PM | #43 | |||
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Re: Whats the point of Front Wheel drive?
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lets say we take your example of a fwd car with a 60:40 f:r weight distribution. now, lets say that instead of using spring rates as a comparison, we use spring frequency, or hertz. wheel hertz more specifically. now. your typical 4dr import sedan has spring frequencies in the 1.3-1.7 hz range. typically, 1 hz is known as the "brown frequency" and makes people get sick, so it is avoided. anyway, lets say that for fun, this car has a front spring frequency of 1.5 hz and a rear frequency of 1.6 hz. this also makes sense as the normal practice for suspension tuning is to make the rear frequency slightly higher than the front frequency so that the cars oscilation front to back will not be un-checked. if they were both 1.5 hz, the car would tend to rock front to back endlessly. the back is made higher than the front because it helps the rear end "catch up" to the front end after hitting a bump. now lets assume that since the rear has a higher frequency, it must have a slightly higher roll stiffness. knowing that understeer is considered safe, an anti-roll bar is fitted to the front of the cars suspension. lets say for arguments sake that the arb contributes 75% of the roll stiffness of the springs. this means that if the springs contribute 100 lbft of roll stiffness, the front arb contributes 75 lbft. i dont know if this is exact, but following your gross estimations, i would not think that this is too far off. this means that the front now has a much higher roll stiffness than the rear of the car and the car has a natural understeering tendancy built in. if a rear anti roll bar is desired to add a bit of "sport" to the feel of the car, one may be added. lets say that the bar on the rear also has a rate equal to 75% of the roll stiffness of the springs. this means that the roll stiffness of the front is still higher than that of the rear, but the rear is higher, as a percent, with respect to weight. Quote:
http://www.sfxperformance.com/parts/HOT804121.htm this is a link to a sway bar kit for a toyota scion xb. it is a relatively well mannered car. notice that the front sway bar is 1.125" and the rear bar is .5" i am willing to bet that you could twist that rear bar with your bare hands. (well not necessarily you, but i surely could.) if you go and look at kits for other popular import cars, you will see a similar trend. in the case of the xb, i am willing to bet that the rear bar is nowhere near 75% of the roll stiffness of the springs. it is most likely nearer to 20% another thing you are overlooking, especially in the case of a fwd vehicle, is the differential. the differential, in my opinion, is responsible for more of the way a fwd car handles than the suspension its self. a lsd with the right tuning (high torque under power, low torque under coast) can give the car LOTS of lift off oversteer. if a car is understeering, all the driver has to do is give it a shot of gas and lift off while increasing the steering angle and voila, oversteer out whe wazoo. on the contrary, a rwd car that has lots of power but is being set up "safely" for understeer, will have a low locking torque under power. this will let the driver have fun getting the rear end out. the coast torque is set much higher though, so that when the driver lets off the gas in the middle of a tail-out turn, the rear will gain traction and come back into the correct line. i recommend this program to you http://www.vehicle-analyser.com/ go ahead and download the lfs version because it includes more car types. play around with it and you will begin to understand what i, and others here are saying. |
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02-12-2008, 08:58 PM | #44 | ||
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Re: Whats the point of Front Wheel drive?
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Firstly, the roll axis slopes up towards the rear on every vehicle I've looked at. That is, the rear suspension roll centre is higher than the front. The roll axis is the result of the roll centre, not the other way around. This is another reason why many production vehicles have sway bars fitted to the front and not the rear. Secondly, talking spring rates doesn't mean much without including the sprung weight at that end. You probably don't realise but the natural frequency of the suspension matters most and rear suspension is often tuned to have a higher frequency than the front. One of the goals is to prevent see-saw pitching. You do not need a "stupidly hard bar" in the rear, I have no idea where you got this idea from, but it possibly stems from you getting the roll axis wrong above. As I've said, normally you need no sway bar in the rear, if you do need to add one to tip the balance, it's rate does not need to be high at all. One of the purposes of a sway bar is to cause faster load transfer to the outside wheels. The higher roll centre of the rear wheel already causes faster load transfer without needing additional roll-stiffness to acheive that. There's a catch with applying theories, the catch is you need to understand them well enough to apply them correctly. I'm convinced that on this subject you don't. |
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02-12-2008, 09:25 PM | #45 | ||
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Re: Whats the point of Front Wheel drive?
I'm going to ahve tos plit my replies to you guys up into parts - there is a lot to say.
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