[s-cars] Quattro - What Don't I get?

[Keith Maddock]

 <calvinlc at earthlink.net> wrote:
> I put both right side tires on ice and the left sides were on pretty good
> pavement.  I dropped the clutch and both right side tires spun like hell
> while the left sides barely turned (both cars result in same).  Is this
> because there is no torque being applied to the spinning wheels and
> therefore the non-spinning wheels don't get much torque either (i.e. open
> diff with a 50/50 torque split)?

Yes - and the reason why you can't apply torque to the spinning wheels
is that doing so for more than a very short time will result in
hitting the redline!   So you lift the throttle.

> I would guess this is why EDL works
> nicely, right?

Yes by absorbing half the engine torque on the low mu wheel so you
don't have to lift your foot off the gas.

> BTW, is the EDL system on the newer A6's pretty much the
> same as what was offered in the UrS6?

Should be fairly similar - I'm sure the newer model years may have
faster reaction time or smoother more accurate control.

> I then reversed it so the left sides were on the ice and both left sides
> spun and both right sides barely turned (same on both cars).

Nothing unexpected there .
>
> I then tried the same thing with the diff lock on.  This resulted in no
> difference with the S4 but a good bit of difference with the 200, i.e. rear
> wheel on dry pavement caught pretty good.  I would guess this means my diff
> lock in the S4 isn't working.  The light comes on and goes off at anything
> over 15 but the rear diff doesn't appear to be locked.  Are there any common
> items that would make this happen?

Check the vacuum lines going to the diff ?

> On a side note since we are talking about differentials; does anybody know
> why it is that every open differential RWD car I have ever owned spins the
> right side tire when the clutch is dropped and never spins the left side
> tire?  I would think some would be more predisposed to left side spinning
> and some more to right...what's up with this.

Some might say coriolis effect?  Take your car(s) to Argentina and see
if it changes sides..

Actually more seriously - most likely it is due to the uneven weight
distribution (especially when only the driver is in the car....  )

Also - thinking out loud - does one half of an open diff have more
mass/intertia than another half ?  The side with less inertia would
initially spin a fraction easier.  Once one wheel breaks traction and
loses traction, then of course then it will be difficult to get the
opposite wheel to spin (assuming actual traction on both sides is the
same).

Cheers,
Keith