Question..... For my 04'C4S, where might I find what the standard power distribution is (front/rear), and what it might max out to when PSM is really-working-hard for a living?

Tx

 

As I understand it, anywhere from 5 - 40 % at the front.

 

Yes. 5~40% to the front but not the normal way. Our cars uses a viscous (read liquid) coupling in the front diff case input. Much like a torque converter in an automatic gear box. The difference is the power transfer is done with a viscosity changing liquid. When there is turbulance (slip between the input and output shaft), the liquid changes viscosity and create a "locking" effect (increase amount of stall). Audi's and Subis, if engine is putting out 100 ft lb, the rear gets 50, front gets 50. When going gets tough, rear gets 35 and front gets 65. On ours, when engine is putting out 100, the rear gets 100, the front gets 5~40. But when the rear brakes are applied by PSM, the rear gets 50, the front gets 2.5~20. Very different. That means if you turn off the PSM, it actually helps you get going in snow and ice as more torque is transfered to the front.

Porsche did this because it makes our cars handle beautifully in the dry and improve feel and driver involvment. At the same time, it could be implemented quickly and cheaply.

Some options:

An open center diff with locking will cost more and screws up the handling of the car at high speed because there is no control over which way the power is put down.

A Clutch type diff, will also cost a lot more. It will also wear out over time and change the way the car handles over it life.

A Torsen (Torque Sensing) diff like quaife will cost an arm, a leg plus your first born and you will have to have 3. In addition, these things makes a lot of heat so some kind of radiator needs to be added to all 3 diff cases (lot of added weight for diff oil and metal radiators).

An E-diff (like the 997 Turbo) that uses electronics to control the clutch actuation will involve cost, weight, and thousands of hours of tuning time.