Originally Posted by greygti

Its actually Haldex, not Torsen. Quattro is a Torsen diff setup. Essentially the car is fwd until slipage is detected and then power is reverted to the rear. It is entirely possible for the car to divert 100% of its power to the rear wheels. Its really a cool setup.

EDIT: check out their page: http://www.haldex-traction.com/default.htm