engine rpm to turbo rpm

[persain488]

what is the ratio of engine rpm at the crank to turbo rpm on any engine?

[FrEaK]

There isn't a fixed ratio... a turbo can spin up to 30,000 rpm the turbo is controlled by the preset dialed in to the sensor..not by the engine speed... the turbine runs off exhaust gas... but the turbo doesn't relate really in anyway to rpms except maybe the amount of exhaust flow at each rpm range...

If you are talking about a supercharger then it depends on your super charger gearing to the crank...