FW: A New Look at Torsens

["Lewis, Gary M" <Gary.Lewis@West.Boeing.com>]

Hi Huw,

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 $hit on everyday
lately.  some of you guys are like seagulls   :-)
Thanks,
Ciao,
Gary


> Here is the current list of questions 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?"
> 
> 
> 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.
> .
> 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.
> 
> 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... 
> 
> 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.
> 
> 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?
> 
> 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?
> 
> 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.
> 
>