[mbtoloczko]

Matt,

It can definitely be used for rally, but it works best when it can run in automatic mode rather than manual mode. To get it working in auto mode would require hooking up all the OEM sensors and controller. Not a simple task on a non-STi vehicle.

By "open" diff, I mean that the clutch will be completely disengaged. The plantary gears will still provide an intrinsice 35:65 (or 34:66) front/rear torque split, but with the clutch completely disengaged, if the front wheels or rear wheels loose traction, then all the power will go to the wheels that have lost traction.

With a manual controller, you'll be able to modulate the amount of clutch engagement which will not affect the torque split but will affect what happens when the wheels loose traction. With full engagement, the front and rear drivelines will be forced to rotate at the same speed. When there is partial engagement, there will be some limited amount of coupling between the front and rear drivelines.

This can be compared to an STi viscous center diff. The viscous center diffs all have a 50:50 front/rear torque split provided by a conventional spider gear center diff. The front and rear drivelines are then coupled using a viscous coupling system. With the viscous coupling, as one end of the car looses traction more and more, the viscous coupling provides a greater and greater coupling action between the front and rear drivelines. The coupling action is strong enough with the STi viscous center diffs that if you were, for instance, to break the prop shaft, the viscous coupler would lock up the center diff and you would be able to continue on front wheel drive alone.