RE: open diffs at the limit.

["Eric Renneisen" <renneie@hlthsrc.com>]

David Eaton wrote:
>actually glen, the point was that with the locked centre, 
>tshift(max) is 100% of torque (to the rear axle) and so is worse 
>than tshift(max) with the torsen which is 70%.  upon regaining 
>traction, you get tshift forward again, etc.  for example, given 
>200 lb ft and lifted insidefront wheel,
>
>locked centre: tshift (to rear) 100 lb ft, torque at front 0 lb ft.
>torsen: tshift to rear 40 lb ft, torque at front 60 lb ft (dictated by
>the bias ratio)

I'm not so sure about this, Dave. With the torsen in this situation, 
you're limited by the torque that can be supported by the wheel 
(driveshaft) with less traction. A lifted wheel can only support 
enough torque to allow it to spin-up. You're saying that the lifted 
wheel can support 60 lb ft of torque. This is very similar to an 
open diff, except that while the open diff transfers the same torque 
to both axles, the torsen will transfer about twice the torque to 
the axle that still has traction. 2x the small amount of torque at the 
spinning wheel = a slightly larger (but still small amount) of torque 
to the other axle.

>traction restored:
>locked centre:tshift to front 100 lb ft, torque at front 100 lb ft.
>torsen: tshift to front 40 lb ft, torque at front 100 lb ft.

Our torsens will be distributing almost all 200 lb ft back to both 
axles, but the rears will receive more torque initally until the lifted 
wheel can support enough torque to equalize. (Actually, the torque 
will be slightly split to the rear until you're out of the turn, but you 
knew that.) My gut feeling is that the manual locker is better in the 
lifted wheel case.

>so the 'spider bite' is much less (better) with the torsen, than with
>the locked centre...

Well, in Scott's theory, the 'bite' has nothing to do with the lifted 
wheel scenario. I do have some problems with his explanation, but 
I don't think the above applies.

Eric Renneisen
'90 CQ 20V  -  my 'racing-iron'  ;^)
Chattanooga, TN