Found this in another thread from the man himself:
Quote:
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Originally Posted by OJEngineering
Let me put my two cents in here. First, turning the supercharger more than 16K or so rpm is not going to net you any real gain. You may see more boost on the gauge but that is from the additional heat. Not air flow. The issue is cavitation. Once you get the superchager rotor speeds above the magical 16K rpm point the air cannot get past the rotor tips and into the supercharger assembly. The rotors just set there and cut the air into pieces. You will not get any more CFM out of the supercharger at those speeds. And CFM is what the engine burns. The engine doesn't burn the boost you see on your gauge. It burns the air the supercharger is pushing into the manifold. Once you get above the point that the supercharger can't fill the rotors you are then just producing hot air which reads as boost on your gauge. So try and keep the rotor speeds relative. I've run the M45 at 16,500 rpm with good results. Above that I've never been very successful. The JR62 has a better inlet window than the M45 or the MP62 so it produces more efficient boost at that same rpm level. But there is no reason to spin the supercharger so hard. There are other ways of making the car go faster.
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Use the following formula to calculate JRSC rotor speed:
Crank pulley diameter / Supercharger pulley diameter x Engine RPM = Rotor speed
Example: 5.7/2.5x7000=15,960rpm