I think you might have better luck driving it with a high speed electric motor than a belt due to the rpm's your talking about.
Hmmm . . . more to ponder . . . Thinking out loud here
Interesting thought, but if Rex is right, you need 100,000 RPM.
1. Is there a 12 (or 24) volt electric motor that will turn 100,000 RPM with enough power to stay sufficiently ahead of the exhaust discharge to be of assistance in overcoming pumping loss, evacuating the cylinder during valve overlap and promote filling of the intake charge? I genuinely don't know.
2. If so, what kind of amperage would such a motor draw?
3. Driving the turbine directly, how would someone insulate such a motor from the exhaust? I suspect direct drive would take heat right off of the impeller straight to the armature and windings. A belt might act to insulate the motor.