RE: Torsens and recovery...

[David Eaton <david.eaton@computerland.co.nz>]

well, before anyone else exclaims about "great handling with the centre
diff locked", perhaps they should have a spin in my ur-quattro, complete
with torsen.  you are comparing different machines, different setups,
not simply open or torsen centre diffs.

much sharper and more nimble, with less understeer than my old '85 (non
torsen) model.  jeff, if you get your arse down here, the ride is on me!

as for handling on the limit,  i've had absolutley no problem with it.
nor did walter rohrl, and i asked him to take it to the limit (on the
track).

apples for apples folks.

dave
'95 rs2
'90 ur-q

>-----Original Message-----
>
>Date: Fri, 20 Feb 1998 08:21:39 -0500 (EST)
>From: audidudi@mindspring.com (Jeffrey J. Goggin)
>Subject: 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
>allo
>cating 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
>  /__| | | / | | __ |  | | | / | |   audidudi@mindspring.com
> /   | |_| \_| |    |_/  |_| \_| |   http://people.delphi.com/audidudi
>______________________________________________________________________
>
>------------------------------