[s-cars] Xi, 4Motion, 4matic

[Keith Maddock]

Mike Sylvester <msylvester at verizon.net> wrote:
> An open diff has a fixed torque split of 50/50 and a locked diff has a
> variable torque split based upon wheel traction and drivetrain friction.
> 
> How do you get a fixed torque split of anything but 50/50 on an open diff?
> 
> Mike Sylvester
> '95 S6 avant
 
Good question! :)  For an axle open differential, I don't know of any
open differentials that have a torque split of anythign other than
50/50.

But for the center position, an open differential can be created using
a planetary gearset that allows a fixed static torque distribution
other than 50/50.
http://www.bmwusa.com/vehicles/3/330xiSedan
and
http://tinyurl.com/5yol3  (Caddy STS)


Further on that, the latest generation of Torsen center diffs are
based on such a planetary gearset, allowing the center Torsen to have
a static torque distribution of, say 40/60, then further bias is +/-
or -/+ from that split   This is used in at least one truck
application that I know of, and I beleive Audi has also toyed with
this if it isn't already in production for them.
(one way to reduce power-on understeer....)
http://www.torsen.com/products/T-3.htm

Cheers,
Keith