Part of the problem comes from saying "torque split" when that's not really what we mean. I had this conversation with MattR a while back, and we figured it out like this:
The power/torque from the motor is fixed to the wheels (I thought it was 50/50 but I guess it's actually 35/65).
What's varied is the amount of speed difference is necessary before the center diff locks...
When the DCCD is set to full forward mode, the center diff is locked, i.e. the front and rear wheels have to turn at the same speed... so while the rears are getting 65% of the power, they are still locked with the fronts. If you jump on the gas you'll break all 4 loose.
When the DCCD is set to full rear, the center diff requires a much higher speed at the rears before they lock to the fronts. So those rear tires are getting 65% of the power and are free to spin wildly while the fronts grip and pull with their 35% of the power. At full rear, the car behaves more like a RWD car because jumping on the throttle will break the rears loose w/o losing the front traction.
Auto mode uses a lateral G sensor to decide where to set the split. I doubt it will ever go all the way forward, because a locket center diff is only usefull on gravel or snow or in the wet, otherwise the wheels will bind up. My guess is that the diff sits at middle ground normally, but will throw the bias rearward under high latteral G's because having the rears uncoupled lets throttle modulation turn the car... i.e. auto mode helps the car to turn more like a RWD car, but gives you additional traction when driving in a straight line.
Bottom line is this: the DCCD is friggen cool!! Damn I want an STi.
