Had a closer look at the clutch code. It is not as bad as I thought. The clutch torque(slip) step function is approximated by a limited linear slope. There is no lockup but a highly viscous coupling. That's why it looked to me like a torque converter first.
The torque capacity is actually the product of the currently used clutch parameters.
torque_capacity = sliding_friction * max_pressure * area * radius
Here a concrete example(CS):
torque_capacity = 0.27 * 0.1 * 0.75 * 11079.26 = 224.35Nm
engine_peak_torque = 243Nm
So the clutch is too weak for this engine of the 911. It is slipping between 4200-6200rpm :o
To fix this the max pressure could be be set to about 15000.
1.25 * engine_peak_torque = 0.27 * 0.1 * 0.75 * 15000 = 303Nm
We should check this for all cars.
edit: Looks like only the CS had this problem.
