[torsen] Re: [s-cars] Torsen torque split clarification

Theodore Chen tedebearp at yahoo.com
Fri Dec 8 02:07:02 EST 2000


--- "Graydon D. Stuckey" <graydon at apollo.kettering.edu> wrote:
> On Mon, 4 Dec 2000 qshipq at aol.com wrote:
> 
> > Audi did it.  That said, you create more heat the more you try to fool the 
> > gears.  Graydon spoke with a T engineer, and found that the shims can be 
> > modified to allow a specific torque split.  Given that audi only sells the 
> 
> Just to clarify that, the engineer told me that you could change the 
> torque _bias_ which as I understand it is the ability of the diff to 
> transfer torque to the loaded wheel.

torsen talks in terms of "torque biasing ratio" (which i mentioned in
an earlier post).  this number indicates how much more torque is sent to
the high-traction wheel/axle than is sent to the low-traction (spinning)
wheel/axle.  it is expressed as a multiple.  so if you have a TBR of
3:1, that means the high-traction wheel gets 3 times as much torque as
the low-traction wheel can support.  the high-traction wheel gets 75% of
of the total torque, and the low-traction wheel gets 25%.  so if the
low-traction wheel can support 50 lb-ft of torque, the high-traction
wheel gets 150 lb-ft.

> As it is, it is a fairly light duty 
> torque bias to preserve smoothness in everyday driving in a luxury car.  

do you know the TBR for the torsen 1 in the UrS4?

> If you increase the friction in the gears though, you can get it to act 
> more like a racing differential, yet retain a fair amount of smoothness 
> that most racing diffs don't have.

to be more specific, it's the friction between the side gears and the
housing.  the torsen 1 has bearings in there.  if you replace them with
washers, thereby increasing internal friction, you can increase the
TBR.  you can also run lower viscosity oil to increase TBR, but if
the torsen shares its oil with the gearbox, you're kind of limited there.
i've been meaning to try redline super lightweight shockproof in my
mustang's torsen, but that will have to wait until i finish sorting
the suspension that i just put in.

note that most of the TBR comes from the design of the unit itself and
cannot be changed to a large degree.

> It was _my_ opinion that if you adjusted the friction unequally (front vs
> rear), you could achieve a static torque bias to the rear so that more
> torque goes to the rear under all conditions.  That might stop the
> instability of the centre torsen a little.  I'd sure like to try it. 

did you ask the torsen engineer about this?

-teddy


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