James Creasy said,
...my neglected ITS car has a welded diff, so its always locked. great on
exit,
can get a bit exciting when braking since if one rear wheel locks up,
they
both do :)
the torsen feels pretty on-off to me, and i notice this in the rx8 also.
the
clutch diffs are very gentle- maybe thats better in a powerful car?
james
OSP - Ouch, Spools Painful
You've probably looked into the why's of this, but.... a locked diff will
tend to power the car straight ahead, which would be particularly bad for
autocross with the high percentage of low speed very tight turns. The action
_will_ tend to make it so that at least one rear tire in those tight turns is
already slipping due to the different lengths of the paths, so perhaps it
would seem like less of a transition when the power is applied. Coefficient
of sliding or spinning friction is significantly lower than when the tire is
still hooked up. (It's said that the highest amount of tire tractive force
available is when a small amount of tire sliding is occurring, maybe 10-15%,
unlike classic problems which simply compare the static and sliding
coefficients.) Likewise, a clutch pack setup will allow some slippage based
on the inside tire having to begin rotating fast enough to engage the
clutches.
A Torsen if I understand it will immediately move the torque applied to the
tire which can resist it. This only happens when one of the tires begins
slipping heavily, commonly under cornering loads for underpowered cars when
the weight is transferred. Cobras probably have "adequate" power at almost
all times at autocross speeds, as per the Mark Donohue definition. :-) (OK,
for all of you others, see http://www.2foolsracing.com/quotes.asp) If you're
used to an open diff, where your cornering doesn't go away when you nail it,
then any diff that will quickly apply all the torque to the loaded outside
wheel may seem sudden.
I haven't actually driven a car that has had both types to compare, in fact
haven't driven a Torsen yet. I suspect I'll learn all this on a practical
basis when my Quaife gets installed, as it apparently operates similarly to
the Torsen. But the difference probably lies somewhere in the differing way
torque is transferred, and perhaps in the transitional behavior of the RX-8.
PaulT
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