Re: Quattro Differentials?

[ti@amb.org (Ti Kan)]

joel nevin writes:
> From my understanding, when not using the diff locks at all, the car 
> isn't really all wheel drive on the 4000q, it is mostly front wheel 
> drive.
> ...

I know we have killed the buzzer, but this is one that warrants its use
IMHO...

All Audi quattro models produced to date are full-time all-wheel drive
(that means power transmitted to all four wheels all the time), regardless
of diff lock settings.  The differential lock design have changed as
the quattro system evolved over the years, but that mainly affects
the car's torque-split characterstics when one or more wheels begin
to lose traction.  The early locking diffs cause a fixed 50/50
torque split to be enforced under all conditions, whereas the later
t*rsen diffs provide dynamic torque transfer characterstics.

I don't want to go into a big discussion about the differentials,
but suffice to say that under normal, non-slip operatiing conditions,
all four wheels on current quattros get equal (or close to equal)
drive power.  The upcoming Audi S4 is supposed to have a slight
rearward torque bias...

> The newer cars, early 1990's and up have a newer quattro system, they 
> use a torque differential, which makes more sense, which is monitored by 
> the cars computer system and is engaged by the system when it deems 

Wrong again.  The only computer-control diff that Audi has ever used
to date is on the V8 models with automatic transmission.  The t*rsens are
not computer controlled.  For the EDL (electronic differential lock)
equipped cars, this name is somewhat of a misnomer.  The differential
itself is not electronically controlled.  The system uses ABS brake
system to apply selective braking pressure to spinning wheels, that is
all.

-Ti
96 A4 2.8 quattro
84 5000S 2.1 turbo
80 4000 2.0
-- 
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