[torsen] RE: Snow Driving

QSHIPQ at aol.com QSHIPQ at aol.com
Thu Dec 12 08:22:10 EST 2002


In a message dated 12/11/02 2:55:40 PM Central Standard Time, 
Dave.Eaton at clear.net.nz writes:


>nope.  you can't change the engine-side torque to the diff other than by
>gearing or speed. "trg" to use your [incorrect] definition (the centre
>torsen doesn't actually have a ring gear, but the carrier is connected to
>the gearbox output).  have a look at a torsen, identify the "ring gear"
>[carrier], look at what it is connected to.  you are mistaking the
>allocation of torque across the torsen with the torque input to it.

The INPUT Dave, is referred to as Trg, so as to not confuse it with Teng.  
The summ of T1 and T2 = Trg.  You are confused a bit because the SAE 
literature references Trg as applied to a rwd vehicle.  In the case of an awd 
audi mit torsen, Trg is before the f/r differential final drives, but after 
the gearing.  So, my statement appears correct, that Trg is reduced,  cuz by 
definition T1(front) +T2 (rear)= Trg, NOT Teng.  As you exceed traction by 
spinning a front wheel, T1 is reduced, so then by definition is Trg.  If I 
don't have that right, please do help me understand.

>The torsen couldn't care if you had a LSD front, LSD rear, EDL front EDL
rear
>it reacts to only 1 EFFECT.  Attempted speed differentiation.  As the
poster
>listed, he was speaking of a straight line, in which case, the torsen will
>work the same with or without locking the rear diff, as would a locker.

>>completely incorrect.  the torsen will react to the loss of traction from a
>>single tyre.  with the normal open front/rear diffs, this has a fundamental
>>effect on the "input torque" to the torsen centre.  a locked or edl rear
>>diff will fundamentally alter this behaviour.

I don't see how Dave.  Since EDL is not capable of crossing the center axle, 
there is no difference in HOW the device works.  You can lock the rear in a 
straight line (as was the example), and the effect on the torsen won't 
change.  As weight shift rear occurs, the fronts will slip first in that 
straight line.  As such locking the rear won't affect the conclusion of the 
characteristics in a straight line.  EDL *might* have an effect, but that 
requires wheel spin first (since EDL is based on wheel speed, not attempted 
wheel slip differences), at which point the torsen has already shifted to max 
rear.  OR, you could propose a start on snow (not what the lister presented, 
but...), in which case there still is no difference, because the fronts will 
spin first, then the rears, but AT max TBR of 78r/22f.  That won't change 
with or without the rear diff locked.  T2 might be higher with rear diff 
locked, but the behavior of the torsen is the same, the torque allocation is 
still max rear.

>perhaps i should also point out the rather obvious inconsistency of your
>statement above "I believe that if a wheel spins, Trg is reduced", with the
>very next one "the torsen will
>work the same with or without locking the rear diff".  ummmmmmm....

Thanks again for reading the posts Dave.  In the scenario presented by the 
lister wrt locker and torsen in a straight line, it would appear that the 
consistency and practical application of the torsen supports the 
documentation and the conclusions above.

HTH

SJ





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