Re: Torsen Tech

["Graydon D. Stuckey" <graydon@apollo.kettering.edu>]

On Sun, 22 Feb 1998 QSHIPQ@aol.com wrote:

> Jeff touched on a couple of points that really hit what the torsen is
> "thinking" while one carves into a turn.  Basically, the unit is sensing a
> slower rear wheel rotation on initial turn in, so more power is transmitted to
> the rear axle, per Jeff's post.  Let's explore that more fully to understand
> the handling of a Torsen at the limit thru a turn.

Since I have never driven a Torsen-equipped Audi at the limit, I don't 
have much to say.   I have used a Torsen in the rear of a small Formula 
car, and I've had them apart - seen inside them.   I've even had the 
opportunity to talk to the development engineer a few years ago who was 
in charge of applying the torsen to OEM apps in America.   That was very 
illuminating...

	What I found with the Torsen was at first a little disappointing
until I understoof how it works.  If you raise the rear of a
Torsen-equipped car like a Miata or something like that, you'll think it
has an open diff since the two wheels will turn opposite directions when
the driveshaft is held still - that is the classic LSD test. 

	But, it turns out that power is transferred from the input shaft
to the two output shafts via 3 little worm/roller gearsets on each side. 
The left worms and the right worms are linked through spur gears, so that
if the right wheel turns forward, the left wheel must turn backwards.  The
kicker though is that it is very difficult to drive a worm gear by turning
the ring gear, which is what you would be doing in the classic "LSD 
Test."  So, down the road, the system works like an open diff, but when 
one wheel looses traction, the diff is sluggish to allow that wheel to 
spin since there is so much friction in the worm/roller/spur gears.   
Tuning that friction, I believe, would be the way to make the Torsen work 
on track.   _I_ would give it a try before chucking it.   You can bias it 
more toward one direction than the other, and you can increase the torque 
bias even more than its current ~75% (I forget what they call that - its 
the measure of how much the diff can apportion torque)

Later,--------------------------- -   -   -   -
Graydon D. Stuckey		 / \ / \ / \ / \
graydon@apollo.kettering.edu	|Mr. Muffler... |
810 733 0255			 \ / \ / \ / \ /
--------------------------------- -   -   -   -