Re: Torsen Torture, pt. II...

[Phil Rose <pjrose@servtech.com>]

>Date: Wed, 11 Mar 1998 19:04:04 -0500 (EST)
>From: audidudi@mindspring.com (Jeffrey J. Goggin)
>Subject: Re: Torsen Torture, pt. II...
>
>>I hold the opposite view.  Until I can recreate the problem to my own
>>satisfaction, it doesn't exist.
>
>Definitely an interesting point of view coming from a man with a technology
>background ... unless you have an idea of what you're looking for, how do
>you know that it doesn't exist?  This is one of the reasons why Monty Python
>never found the holy grail ... or did they?  I forget ... time to go feed
>the dead parrot.  :^)
>
>>If, indeed, there is this exposure with a central torsen differential -
>>where
>>is the public documentation?  Where are the recalls to change percentage
>>limits?  Where are the cautions in the owners' handbooks?  A quick search on
>>Alta Vista reveals that _lots_ of cars use torsens in different ways - but
>>there's nothing, absolutely nothing, to support some of the wilder theories
>>of operation posted here.
>
>I suggest that most people who *have* experienced it, probably didn't
>realize it ... all they knew is that the car was out of control.  Secondly,
>even if they did know what happened to them, they probably realized that it
>would be best to keep their mouth shut since it is, by default, evidence
>they were driving MUCH too hard for a public road or conditions.  This is
>especially true if an accident was involved...

Hmmm.

Many of you recall my tale of woe a few months ago ('91 200q on its roof).
Later, I responded to one of Jeff's first posts in this thread because I
had been searching to understand the cause(s) of my accident. In three
months of head-shaking, hand-wringing and sleepless nights (believe this,
friends!) I have not been able to rationalize--based of 40 years of fairly,
uh, serious (and sometimes organized competition) driving--what happened to
me and my quattro. Yes, it's true we hardly knew one another. So I'm not
_at all_ willing at this point to cast "blame" on the machine. But neither
am satisfied yet by admonitions such as "you shouldn't have lifted off the
throttle" or "coulda recovered just by re-applying power". If following
these instructions -- the one impractical and the other, counterintuitive
-- is required to survive when  below any perceivable limits, it would make
me want to seriously rethink--in as positive and rational a way as
possible--the Audi Torsen experience.

Would my accident have been avoided by driving slower? Well sure, just as
virtually _all_ accidents can thus be avoided. The bottom line was that the
car responded altogether unexpectedly and then, violently during a routine,
nearly straight-line situation followed by a standard recovery response
(steering correction). Was this a manifestation of the "bite"? I dunno.
Maybe. Probably not. So, I simply was driving foolishly at 11/10ths? Well,
when you have to crawl from your vehicle on hands and knees, I suppose it
is 11/10ths, by definition (or "default" as Jeff says) for that particular
car/driver/road combination. But I'm reasonably certain in my gut (although
can offer no proof) that I would have gotten through it in my '89 100 (fwd)
with little or no incident.

Anyway, since my trouble started "off-throttle", what I've been focusing on
is the question: how does the Torsen differential in the 44 chassis Audis
behave in the *coast* (i.e., engine-braking, not "drive") mode? For
example: the Gleason paper indicates that the in coast mode both of the
side gears move toward the *opposite* end of the differential housing (than
they do in drive mode). This, they say, gives the opportunity to design in
a set of frictional characteristics different from those used in drive
mode--thereby obtaining a *different* bias ratio for the torque
distribution in coast mode (vs. drive). This is said to offer ability to
compensate for things such as "undesirable steering effects" associated
with downshifting, etc.

Well (I ask naively) has Audi used this opportunity to have different
drive/coast bias-ratios? I would guess so. And if so, did they do it the
*same way* in all versions of the Torsen? In other words, is the center
Torsen made with _exacly_ the same bias characteristics in the urqs as in
the large-chassis cars? Is it not conceivable that the Torsen drive/coast
bias ratios are different (better optimized?) in the urq and RS2
applications than in (at least some of) the large chassis applications?
Would have some bearing on a possible difference in bite susceptibility?

I'm in waaaay over my head here, but I'm learning one hell of a lot about
Torsen differential theory. Don't tell anyone, but a year ago I thought the
Torsen differential was invented by some Scandinavian named, uh, well...
never mind. :)

BTW, with all the gear talk, it is interesting (for me at least) to reflect
on the fact that I live directly across the street from the house built and
occupied for 40 years by one Ernest Wildhaber. Mr Wildhaber was a mainstay
of the Gleason Works Research Department and a world authority on gearing.
He had over 300 gearing patents and is credited with the invention of the
hypoid gear. I would venture that he certainly helped to put Gleason on the
map and set the stage for eventual development of the Torsen differential.
He died in 1979 at age 86.


>I'm certainly curious about your results but, like I said, I think getting
>caught up in this "my car/your car" circle is ultimately going to accomplish
>nothing until we first reach a consensus about how the diff works...

Amen.

Phil Rose

Phil Rose		Rochester, NY
'89 100			pjrose@servtech.com