ProCharger C1: pulley sizes and rpm limits

Bored one day and figured out the limits of the C1 ProCharger unit on the QR25 motor, and how high one could rev with different sized pulleys.

Some basic specs on the C1:

max rpm: 80,000rpms

max flow: 1000cfm

max boost: 24psi

internal step-up: 4.70:1

Stock QR crank pulley diameter is 5.75"

ProCharger pulley sizes I calculated for are 2.25" (~14psi @ stock redline) and 2.55" (~10psi @ stock redline).

First the 2.55" pulley... 5.75 / 2.55 = 2.255, meaning the supercharger pulley spins 2.255 times for every one rotation of the crank pulley. Multiply this number by the internal step-up ratio of 4.70:1 and we get 10.5985 rotations of the C1 impeller for every one rotation of the crankshaft.

Assuming that 6250rpm is the stock rev limit, the C1 will be spinning at 66,240rpms with the 2.55" pulley at stock redline.

If we pushed the C1 to the limit of 80,000, you could rev up to 7,548rpms on the QR with the 2.55" pulley.

With the 2.25" pulley you would have a crank to supercharger pulley ratio of 2.555.

This means if you were to max the C1 out, you could rev up to 6,661rpms on the QR with the 2.25" pulley.

How much boost the C1 would make at those rpms is speculative at best.