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TORSEN |
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Don't run! Don't hit delete! This is the nice version...
Subject: A New Look at Torsens (10/19/99)
From: Gary Lewis Gary.Lewis@West.Boeing.com
Can you please post the comments below on a webpage and update/track them as we (you, me, the Audifans list, etc.) see fit.
One note to the list: I don't own this stuff, so let's call me a Trustee for the moment (and I ain't gonna be a judge or arbitrator), unless someone can think of a better name (and be nice. I've been getting pooped on everyday lately. some of you guys are like seagulls :-)
Thanks, Gary
Here is the current list of theories in response to the question:"Why is it that Torsen equipped Audi cars in America experience a handling condition at the limit in turns that renders the car uncontrollable (nicknamed 'Spiderbite'), while Torsen equipped Audi cars in other countries such as New Zealand and Britain do not?"
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1. (Phil Payne.) Possible differences in the specification of the alignment job itself, _NOT_ the actual numbers used. Hints have suggested it's a 'less than one hour' job for US dealers, whereas Audi in Europe allows two hours and BR Motorsport frequently take three.
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2. (Jim Haseltine) Where the driver sits. Dave & Phil sit on the right-hand side, Jeff & Scott on the left, so the cg of their cars are different. Now unless Audi build cars that have a cg on the centreline when unlanden (bet they don't) then the cg's when loaded will be in different places, not just displaced by similar amounts left or right. We probably all know how the positioning of a load can affect the handling of a vehicle. I'm not saying that this is the answer but it could well be a contributing factor.
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3. (Jim Haseltine) maybe a combination of the different cg and Ur-q chassis/suspension have moved the bite point outside the handling envelope of an Ur-q? Before the Torsen reaches the 'bite' the driver has already lost it...
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4. (Gary Lewis) Is it possible that some components between the Euro vehicles and USA vehicles are different? I do know that the right hand drive vehicles have different parts, so there is one example. But what about gearing and differentials, other driveline components? We admittedly get the shit stuff here in the USA, maybe we got the retards version of a torque sensing device.
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5. (Phil Payne) Bad translation by Bentley?
I only have the ur-quattro running gear microfiche here. In both English and German there is an error that was corrected by a Bulletin to be filed in the microfiche folder.
So much is copied between the hydraulic lifter quattro microfiches (the ur-quattro gearbox fiche refers the reader to the 200Q fiche in several places) that it's entirely possible such an error also exists (or existed at one time) in the 200Q fiche. I don't know - I have to view a copy.
I also don't know why the US source for this information in Bentley - all of the material is available in English on real Audi microfiche. Audi, though, send out periodic corrections. Does Bentley?
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6. (Mike Mulholland) dave and phil and (name deleted on request) drive their torsen equipped cars hard primarily on highways and bi ways. I would bet that they don't use the same _track learned_ driving techniques on the roads they drive because they are doing it for sheer exhilaration and joy and not to earn a competitive advantage. dave mentioned that walter rohrl drove his torsen ur quattro around a track _very_ competitively with no problem. but was it under race conditions or just fast.... from my bicycle racing days (canadian champion) I know that many can go fast, but in order to win you go where others fear to tread. the risk is to crash and burn _or_ to win. winning was always worth the crashes used to learn how to win. so although walter is a professional racer with a skill level possibly higher than scott and jeff, he had no problems in a torsen ur quattro at the limit on the track. so is the difference possibly driving technique?
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7. (Kirby Smith) I suggest that while alignment can change a car's intrinsic handling (U or O) and thereby make the vehicle more or less controllable, a U-O-U oscillation, such as reported by Scott and Jeff, requires two lags through the servomechanism made up of vehicle and driver. Where might these lags come from? One is from chassis dynamics, i.e., the delay in vehicle attitude and slip response due to a steering input. The second, I assert, is from the driver, i.e., the delay in steering response due to a "seat of the pants" input. If these times are commensurate in a given servomechanism, and the "gain" is high enough, the system _will_ oscillate and likely go unstable.
Notwithstanding how well any of the "protagonists" understand, or agree upon theory, we have to take at face value that competent drivers have achieved different results. This suggests to me that they, together with their cars, either have different pairs of reaction times or different "gains" or both.
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