[urq] 01E Torsen Madness

[qshipq at aol.com]

 Hey Andrew
It took a while for me to study and understand the Wavetrac operation.  I'm not sure that is the answer, probably better than a torsen, but it still isn't going to act like a locker under braking.  The Wavetrac works the same way Left Foot Braking works on a Torsen.  If there is no load on a torsen (wheel lift) there is no drive to the wheels (0 x TBR = 0).  What many have found out is the Torsen can be fooled by using the brakes to add load to the slipping axle.  The Wavetrac appears to work the same way, but it just internally adds load to the axles by forcing the axles to 'climb' the wave profile built into the axle, forcing 'load' on both axles regardless of traction.  For more on how this works
http://www.wavetrac.net/technical.htm
That 'preload' is also adjustable, but I really don't see that being so high as to assist in Ideal Brake Force Distribution.  Put another way, if you preload the Wavetrac enough to bring on Ideal Brake Force Distribution, it will likely not really be any more driveable than a locked center.  Further, if you envision a braking scenario where a rear is 'impending' lockup, you will be bouncing up and down that wave profile at the same time you are trying to 'unlock' rear brakes.  IMO, this will be worse under braking than a torsen, as in a straight line (acceleration or deceleration/braking) the torsen is consistent in allocation of torque, which means it will not 'interfere' with braking. 

I see a lot of hype on MG about modifying a Torsen to be "High Bias" ala Stasis modifications.  The fundamental problem with this mod IMO, is almost every quattro car is a static understeering chassis.  Which means, if the rear wheels lose traction from this modification, the car will understeer when the (TBR x 0 = 0) occurs, OR the loss in traction shifts torque forward.  In a street car, the effect of this will be a spider bite later in the turn (after apex vs at the apex), but IMO, it's not able to eliminate it.  Add in more rear bar, also adds more propensity to lift a wheel, which then brings you back to the 0TBR formula.  

I'm quite surprised that Stasis hasn't moved to the clutchpak rear diff as Jeff G proposes.  The key to any of these TBR mods, is to keep the traction at the rear.  An open rear diff or a torsen rear diff won't do that in a wheel lift scenario, because you are back to the 0TBR problem.  Plus a torsen rear that goes up in the air, then hits the ground has a tendency to explode, btrepaired that.  Back to your quandry.....

For a non-abs car, adding a torsen is fine for 9/10ths of driving.  However, a 'big' issue of brake balance comes into play, which the torsen also affects.  I expect to see a lot of problems with retrofitted torsens in a performance environment, and the gains going back to the guy with the locking button for his center diff.  What we fail to point out in many of these discussions is, the locker center in 'open' mode, is still awd, and also 'fine for 9/10ths of driving'.  Go to the track, hit the 'predictable understeer' button, then unlock and drive home.  After 32 years of FWD/AWD cars, I fail to understand such a grand fight of the laws of physics.  I have no problem with understeer, make it really predictable - that's the goal.  The unfair advantage to a locked center then, is much better braking, especially in the non-abs cars.

my .02 arbitraged thru the peso

Scott J
Torsen 4kq
Locker everything else

 

-----Original Message-----
From: afinn1 <afinn1 at gmail.com>
To: urq at audifans.com
Sent: Wed, Apr 6, 2011 12:13 am
Subject: [urq] 01E Madness


With all this talk about torsens it has me worrying that the 01E that I had planned to install in the urq v8 will disappoint. I really rely on that locked center dif in my 016 as a poor mans antilock. Is there a lockable center dif for the 01e? Anyone tried the wavetrak differential? It claims to be preloaded. Would it lock under braking? Any thoughts appreciated. Sorry if this is a duplicate post. I think my last posts got lost in the server hiccup. 
 
Andrew Finney