re RE: Torsen post for Gary

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

Kirby Smith prescribes:
> Put a torsen quattro (with matched tires and zero toe and 
> camber on all wheels) on a pair of chassis dynomometers. There 
> should be no slip angles involved.  The dynos are operated at 
> the same speed, and initially at the same load matched to the 
> drivetrain output power.  Now reduce the load on one dyno 
> slightly.  Does the torsen apportion torque to the dynos at 
> less differential than the bias ratio?  Or does it attempt to 
> speed up one end by forcing torque to that end at the bias 
> ratio?

You're use of the word "differential" here is in a different 
context from mine (and Stan's), but I'll have a go at this 
anyway.

The answer depends on the load difference between the two 
dynos. My understanding is that the Torsen will act just as a 
locked diff as long as differentiation is not occurring (i.e., 
both driveshafts turning at the same rate). Therefore, as long 
as the load of one dyno is at least 50% of the other (25% vs 
75% of the total torque being delivered), the Torsen will vary 
the torque between driveshafts and keep them both at the same 
speed. 

If the load of one dyno goes below 50% of the other, then 
differentiation will occur--the end with the lower load will 
spin faster relative to the other because it will still be 
receiving 25% of the total torque (half of what the other end 
is getting), but its load is lower than half of the other end. 
Another way to say it is that the end with the higher load will 
begin to spin slower relative to the other, because it can only 
receive as much as double the torque that the other end can 
support, but its load is more than twice as much.

That's the way I see it, anyway. If I've screwed up somewhere, 
will someone please tell me?  (Yeah, like that request was 
really necessary!)

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