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Torsens and recovery...
>Jeff Goggins post about why it is hard to gather a sliding Q was the
>clearest explanation I've yet read. And I think from my own experience
>that it relates more to the non-torsen 50:50 split cars than Torsen.
I agree ... I've also got a Torsen-equipped car and find that it behaves
entirely differently. Of course, the cars -- Ur-Q and 200q -- have a lot of
other differences so it's a bit of an apples-v-oranges comparison but I have
divined some trends regardless.
>At the NEQ WDS from watching the torsen cars and riding in them I'd say
>they broke into oversteer far sooner than a non torsen car.
I have also noticed this. I'm still trying to figure out the reason(s) why
this is so but offer the following as speculation: Although the Torsen is
claimed to be a "TORque SENsing" differential, it looks to me like it's
actually sensing this indirectly, by reacting to differences in the
rotational speed of the front & rear diffs ... the faster turning one is
presumed to indicate a spinning wheel and this is further presumed to
indicate a lack of traction at that end of the car relative to the other.
The Torsen diff automatically redistributes the available torque between the
front and rear diffs accordingly and if all goes well, the diff speeds will
start to equalize in response. To the Torsen, equal diff speeds is presumed
to mean maximum traction utilization.
However, not all differences in rotational speed are due to wheelspin,
especially when cornering. In low-grip conditions, it's possible for a
wheel that's sliding sideways to turn *slower* than the other wheels and if
it happens on a Torsen-equipped car, the center diff can be fooled into
allocating it even more torque still, the last thing it needs at that
particular moment ... this is how little slides quickly become big ones!
Another factor to be considered is that due to the continuously variable
torque split, modulating the throttle of a Torsen-equipped car has less
predictable results ... unlike an AWD car with a locked center diff (a 50-50
torque split), the effects of doing this DON'T necessarily cancel themselves
out front-to-rear. This is why I find my 200q sometimes behaves
schizophrenically: At times, it responds like a FWD car and at others, like
RWD ... rarely does it respond like I think an AWD car should. Worse still,
it's impossible for me to predict how it will respond at any given moment:
While on course at an autocross event, I've had it respond like a RWD car at
one corner only to respond like a FWD car at the next one ... needless to
say, trying to drive it at 10/10s under these conditions is difficult, if
not impossible (for someone of my skill level, anyway).
That said, I personally think the Torsen works better for most normal street
driving ... of course, driving in the rain and snow may be another matter
(and, fortunately for me, one that I don't experience very often!).
/ | _| o | \ _| o Jeffrey Goggin
/__| | | / | | __ | | | | / | | firstname.lastname@example.org
/ | |_| \_| | |_/ |_| \_| | http://people.delphi.com/audidudi