Reprogramming a Prius to Keep the electric motor at maximum torque.
 

My 2011 Prius Hybrid uses two electric motors to drive the car through a planetary gear set, By varying the difference in speed between one motor and the other, the proper output speed is achieved to the drive axles.

I know that an electric motor's torque is highest at stall, and decreased as the motor's speed increases.

Does anyone have an idea on how to regulate the ratio between the two electric motors so that motor speed is kept low, and torque high at any vehicle speed?

Is this already done by Toyota?

I know the idea would be more useful in a purely electric car, but could benefits be recognized in a hybrid as well?

What may be the pitfalls?

Maximum torque and maximum efficiency are not the same with electric motors. As you point out, maximum torque is at stall, which is completely inefficient. A non-spinning motor at maximum torque is doing no work because horsepower is calculated by (torque * RPM) / 5252. The result of zero RPM is zero HP.

I'm not clear what the most efficient RPM and torque % would be on an electric motor, but it's a way more linear relationship than with petrol engines. Auto manufacturers would certainly attempt to keep them in optimal operating ranges.

MODs- This should probably live in General Efficiency discussion or Fossil Fuel Free

Thank you.