[torsen] Re: "Care to Comment" -> differential t...

QSHIPQ at aol.com QSHIPQ at aol.com
Tue Apr 9 00:51:41 EDT 2002

WHOA up boys...  Torsen nerd hat on....  What Stasis is doing directly 
contradicts what all the S4tt boys do in the motorola cup,  more 
specifically, they weld the baskets solid for faster laps.  Extending the 
S4tt bias ratio *can* put UP TO 80% rear bias, but the problem with that is 
that once traction of the rear wheels has been exceeded, then even more 
torque shift will occur to the front.  This is also specific to the S4tt 
which has a static 55/45 split, NOT the URS4's which have a static 50/50 
split with a 3:1 bias ratio.  Further research would show that the torque 
split of the urs4 is 75/25, or 78/22 (whomever you want to believe) which 
equates to 3-3.5:1.  500 bux to go to 4:1 sounds expensive, and exactly the 
wrong way to track any understeering quattro.

I've been on the forefront of the torsen center (in)capabilities for quite 
some time.  I read the below, and I wonder how exactly shifting more torque 
front to rear at the limit of adhesion can yield better lap times.  
Especially when the S4tt race cars that win *championship* races aren't 
extending the BR to 4:1, they just lock the diff solid.

Someone hasn't done their homework, and is selling hard.  I'd be happy to 
have a on line discussion with any Stasis representitive.  Or they could sub 
to the torsen list, but it would be a tough road, and I'm biassed (pun 
intended).  I'd say the BS words but I'd sure like to hear the logic.  I'm 
intrigued too at the formula for sec>HP conversions, I haven't seen that one 
yet.  I'd add the 60hp before I'd mess with the torsen in any S4tt.  

Scott Justusson

In a message dated 4/8/02 2:53:00 AM Central Daylight Time, mlped at qwest.net 

Sorry Rob, I should have read your post more carefully all the way to the

So I take it Stassis Engineering does exactly that, offer "blue printed"
center differentials etc.?


~-----Original Message-----
~From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
~Behalf Of quattro-request at audifans.com

~   1. Care to comment? (Rob Andrews)
~From: "Rob Andrews" <randrews at sbcglobal.net>

~From stassis engineering....
~Differential Tuning
~Tuning the center differential provides one of the most significant
~performance gains available to the Quattro owner. The standard
~torsen center
~differential in the S4 and A4 provides a 2:1 torque distribution
~This enables the end of the car with traction (generally the rear) to
~deliver twice the torque being delivered by the least tractive end of the
~vehicle (generally the front). For high performance street cars, we
~recommend a bias ratio of 4:1. This is the same bias ratio that Audi has
~provided in the stock RS4 driveline.
~In professional competition a high bias center differential provided a
~performance gain of almost 2 seconds a lap. This is the equivalent
~of adding
~60hp to an S4. This is our first step in almost every tuning project. It
~provides a measurable performance gain for track-oriented drivers. For the
~enthusiast street driver in good weather conditions, it can provide the
~balance and control of a rear wheel drive vehicle, as 80% of the cars power
~will be applied to the rear wheels upon corner exit.
~The center differential in an S4 is a slip in cartridge accessible from the
~rear of the transmission. The A4 center differential is a self-contained
~bolt on unit. Install time is approximately 2 hours.
~Center Differential rebuild A4/S4 - $500
~Rob Andrews
~99 A4 2.8QS   83 Ur-Q

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