Hi, the pump when it spins fast enough becomes a rotary compression engine. The air is compressed along the spiral path and explodes when the phase changes occurs at the periphery. The four stroke cycle happening along the spiral path. What Tesla is saying is the pump becomes a motor and become self regulating like a DC motor. What would be really helpful is being able to work out what motor would be needed. I’ve just tried a 4hp motor and it ran out of torque using 2.2:1 at 2100rpm. So at a guess I would now think perhaps 10hp would be a big enough starter motor. However I would need a new controller and bracket. So instead I’m opting for an aluminium rotor instead of a mild steel rotor as it should be approx 11-12kg rather than 27kg. My aim is to prove this is a rotary compression engine ASAP as if it is that would be world changing!