[s-cars] ... Differentials, locked v edl v torsen

[QSHIPQ at aol.com]

Saw the thread, here's some thoughts from Torsen Boy (tm).  First, there is
absolutely no reason why EDL won't work with Torsen rear.  Remember EDL is
based on wheel spin, torsen is based on attempted speed differential.  So a
torsen will allocate to maximum TBR before EDL ever engages.  EDL also
disables at 40mph, so torsen is complementary below 40, better than open over
40.

Remember the audi v8 used torsen center and rear for years, so all we are
really talking about is the addition of EDL.  I do question how a rear torsen
will affect my spider bite (tm) scenario, but my brain thinks a torsen rear
will help raise the bar in handling vs open.  My only concern would be in the
shift off all torque forward with rear spin up, since a torsen rear (with
torque allocated rear) will put more torque to the ground, that's more torque
shifted forward under break away conditions.  When this happens, the fronts
will overload more quickly than a car with an open diff.  The good news is it
should take longer to get there.

Yes Keith, Alex Neckus intention was to put torsen F/C/R in his 4ktq racecar.
 Both Ned and I advised against it, and in fact, I wrote Alex several posts
trying to talk him out of it (the front that is), last I remember, I was
successful (long diatribes on audisport cars).  The problem with front LSD on
awd cars is that they add understeer and also add a lot of kickback into the
steering wheel.  I drove several toyota 4 runners (this is a pretty well
recommended mod) that had front torsens, and wouldn't consider one without
the lockout hubs, which is the recommendation of the 4wheeler rags as well.
The understeer on road was noticeable, so much so that low speed turns were
all that one felt comfy in.

I've also driven the 95 S2 rally car with locked f/c/r (as audisport spec'd)
over the years, and it's like driving a crab, in a turn, you immediately look
to what's beside you, not in front of you.  It also tends to eat clutches,
but for high hp applications, it's THE way to get the power to the ground
(read: any 1 wheel is capable of supporting 100% of engine torque).  Street
car?  Forgetaboutit.

If you look to audisport use of LSD fronts in factory works cars, the
documentation is pretty thorough.   They tested all types thru the years (and
interesting- boring- another post) and finally settled on 80% LSD rear
(torsen/vc/clutchpack), locked center (rally cars always) or LSDC (tarmac
race cars - fixed split), and fronts were either locked, open or 20% LSD in
the rally cars (driver preference), open in the tarmac cars.  The trend was
to lockumup as the HP went up.

Specific to this list, before I'd ever consider a LSD front, I'd get the rest
of the equipment optimized.  Such as: front swaybar, optimizing ackermann
effect, increase durometer readings of select rubber bushings, dedicated
seasonal/track tires, and steamboat, and other track events that teach you
better driving techniques.

In terms of the torsen rear, I'm adding them to a couple cars for the 2003
season, all of them locked center cars tho.  WRT this list, the torsen rear
should prove to be a good bolt in modification to any S car with locked or
edl rear end.

HTH

Scott TB J
Lockers aplenty
Torsens to the back of my bus....