[torsen] Torsen 3

[QSHIPQ at aol.com]

Justin:
I might suggest that you try a couple things first.  To get awd to 
"oversteer" in audi/vw applications is tough, cuz they are front heavy pigs prone to 
understeer as they are all awd adaptations of FWD.

A larger TBR has some problems with it in the T1/T2 variants.  You are 
increasing TBR from a baseline of 50/50, so your "stretch" is even.  IOW, you 
increase TBR to 80/20 from 75/35, you go to both ends of the axle.  Which means that 
you could get the benefit of more oversteer, but you also get the downside of 
more understeer at the opposite end of the handling spectrum.  

The T-3 as Keith suggests is going to be next to impossible to "modify" 
without regearing.  Then, even if you do, your lockup is limited with planetary 
gearset torsens.    

Your descriptions below don't appear to be a diff problem...  Yet.  I see 
overloaded tires with a massive weight transfer due to good brakes, I see a 
continuation of that overload thru the corner.  First, a tire switch.  Get the 
hoosiers and try again.  Then, I suggest playing with wheel width and tire sizing 
to put more tire patch in front, and less in the rear.  Then, I'd suggest 
messing with swaybars/spring rates -  front and rear.  Then I'd suggest looking 
hard at the rear diff (as in a locker or torsen rear).

The T-3 is a very new unit, and I really think that the "success" with 
messing with the T1/T2 torsens that Stasis had was due to changing too many factors 
at once (in the datalogging  thread I read, they changed TBR in the center AND 
added a rear diff - my argument was they needed to leave the TBR center and 
JUST change the rear as a baseline). 

The big problem with a torsen is that eventually you will overload the rear 
with turning radius and torque, then you will get more understeer as torque 
shifts forward.  I say leave the limited TBR and get oversteer "GIVEN" the TBR 
you have.  As Jeff Goggin said years ago (a fellow fwd racer) why fight the 
front driver character of the car, think of it as a fwd car with more traction.  
Then look at the problems again.  And, keep in mind that with a torsen in a 
track environment, you want more lateral slip, but also more rolling diameter 
since the torsen is only looking for axle speed differential, not "traction" per 
sae.  So keep the torque at the rear as it steps out.  

I think further, that what you are looking to spend money on here for a 
couple years anyhow (until T-3 are as common as "university specials"), can prolly 
finance a better tool for the job (read:  dedicated track car).  


HTH

SJ

In a message dated 1/6/2004 9:00:09 AM Central Standard Time, Justinw at rga.com 
writes:
Scott

Thanks for the suggestions...

Just for the record, I've been driving on the track now for 2 years with the
Passat.  I use a set of 17x8.5" SSR competition lightweight wheels with a
set of summer tires(Yoko ES100s and switching to Hoosiers).  I've upgraded
the braking system with stainless steel lines all around along with the BIRA
level 1 upgrade using the porsche boxster calipers with larger rotors.

When I come out of a hard corner I get alot of understeer which requires me
to let off the gas and loose a gear when I'm in the sweet spot of the power
ratio.  The other problem is that during hard braking just before these
tight turns the front end tires heat up too much, due to the hard brake
situation and then trying to immediately get back on the gas to get the
monster to turn in.

I spoke directly with Paul at Stasis Engineering about his race applications
that swap out the gearing in the center differentials to achieve a higher
TBR to the rear in the above situation.  The rear diff change would mainly
be to increase drag style track racing by moving most of the TBR to the rear
and similiar to the front change.  The Passat weighs alot and power is only
about 200hp/190lbs so I'm looking to get the most out of the driveline that
I can.  I would have purchased their upgrade on a trial basis but we later
found out that the  new model Passats use the T3 and they've never worked
with the newer T3 or an automatic tranny.  So my agreement with them is to
find a working model (flow charts and such) or ship them an entire assembly.


I've emailed Torsen a number of times along with some other contacts that
were suggested and I've gotten no response.  I've even gone along the lines
of requesting info through the torsen academic programs, to none avail.

Thanks all

Justin