[V8] Torsen and Stasis...I've driven them both, for what it's worth

[QSHIPQ at aol.com]

Excellent post Carter!  Copied to the torsen list....  This goes  a bit 
beyond the original question from Andy, but definitely worthy of  consideration.  
Andy, I understand that you converted to a 5spd, and IMS,  there is no way to 
keep the clutchplate locking center, which means you've gone  to torsen center 
torsen rear.
 
Your original question was regarding torsen rear, which again, for a  
street/track car is just fine.  I've set up type 44 with locking center and  locking 
rear as well as locking center torsen rear.  IME/O, the locking  center torsen 
rear gives the best handling on the type 44, even after optimizing  the 
chassis for track.  Randy Pobst drove the 5ktq setup (center lock,  torsen rear) at 
BIR nationals a few years ago, and his comments were all  positive.
 
The biggest issue you run into with the torsen center is the amount of  
weight shift on the v8 causing some handling issues under spirited  driving.  Given 
the choice in a 5spd v8, I'd want a locker center/torsen  rear for daily 
driving.  That said, a torsen center torsen rear is hardly  last prize at the 
county fair, and for a v8, is probably a pretty good  compromise.  And that's what 
the factory did anyhow. 
 
All that said, unlike the Stasis wide TBR, on a street car I'd prefer to  
make a narrow TBR so it has less dynamic chassis effect (like what audi did with  
the second gen rear bias torsen).  A lot of suspension work has to be done  
to really make a wide TBR be 'better' than stock or narrow, and the v8 is  
already quite the portly beast.  You can probably get better  handling results 
going after dedicated wheel tire combos  (winter/summer/track) and brakes to get 
better v8 performance than changing  around the diffs.
 
HTH
 
Scott Justusson
In a message dated 3/12/2007 4:58:21 P.M. Central Standard Time,  
carterjohnson3 at yahoo.com writes:
Hey guys, 

I  drove a 93 V8Q as my daily driver for about 2 years, and got to know it 
quite  well.  I took it to three winter driving schools, though never to the  
track, and never pushed to hard enough to matter on the street.  The Torsen  
rear/auto combo in the V8 with snow tires is - hands down - the best Audi I've  
driven in the snow.  That includes all the new models save the A8.  It  was 
certainly better than my 4000Q, and is better than the 200.  I think a  lot of 
that had to do with power to weight ratios, and balance - it was much  easier to 
balance the V8 on throttle than it is the 4000 or 200.   

This past fall at Mont Tremblant, I got to drive a  fully modded 2.0 Turbo 
A4, replete with Stasis modded Torsen diffs.  In  terms of track driving, it was 
the most oversteering car I've driven on the  track, and I've driven quite a 
few.  It oversteered underpower and off  power, neutral input, mild turns and 
hard turns.  Part of that was the car  setup - 800lb springs in the rear will 
certainly help when not on full race  rubber - but you could also feel the 
power delivery shift under heavy  throttle.  It was a neat mod, though I wouldn't 
want it day to day, as  Scott said - it was really intended for track use, 
and could certainly catch you  out if you weren't paying attention.  I'm fairly 
smooth on track,  especially when it's not my car, and I had the thing 90 
degrees to the direction  of travel on the warmup lap, completely unintentionally. 
 It was much like  driving the V8 in the snow.

I've also driven RS4s and  RS6s, which seem to overly suffer from the high 
speed/fast turn  oscillation.  At Tremblant, this is pronouced through turn 6 -  
approximately 90mph at entry flat on the floor and lots of steering input.   
Both cars have an uncomfortable understeer/oversteer wiggle they develop at 
that  speed.  With some experience under my belt, I didn't lift when this  
occured, though I could see easily how someone could put one of these cars in a  
wall if you snapped off the throttle at the wrong time.  The B5/B6/B7 S4's  I've 
driven on track don't seem to do this as much - it's more just constant  
understeer, so I presume the R's have reprogrammed Torsen setups and probably  too 
much power :-)

For track driving, the Stasis  setup is very trick, if you can live with it.  
In the snow and ice, the new  cars do WAY too much thinking for me, though in 
general I'm sure they're safe,  there are times when I want the car to 
oversteer - or even, just to turn - and  the new cars simply won't let you.  On the 
new new models, they've gone  Daimler - even if you disable the ESP, it stays 
on.  

For what it's worth, that's my input.  The V8 stock setup is  certainly good, 
but only with proper tires.  In a track situation, I can  see wanting to bias 
that power more to the rear and have maybe a more constant  limited slip, 
though it would be interesting to know what Audi ran for  center/rear diffs in 
the V8 touring cars.  I presume they ran a much more  rear-biased, locked up 
setup, given the videos I've seen of those cars  turning.




W. Carter  Johnson
SileStone/Stone Systems of New England
401-573-2399
 
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