All things being equal, as you move to bigger SC'er units(or turbo units) how does it effect where you make power. Example: going from a P1SC to a D1 to a D1SC to an F1, etcc. Assuming the engine is built for FI, has ported heads and a blower or turbo cam to match. Reason I ask is b/c I'm wondering how much more power I can make at the same psi on a D1SC vs. F1 Procharger. I also want to know what that's going to do to my rpm-powerband range. Thanks

 

I think the RPM powerband would be around the same. You will just make more HP at all RPM's with a larger supercharger.

If you were switching from a supercharger to a turbo - then it would be a different story

The cam you have is the biggest determinant of where you make power in the RPM range

 

When you choose different superchargers, you are choosing a different compressor alltogether. Each combination of housing and compressor wheel will produce different results for different engine and chassis/suspension combinations. For simplicity's sake, the largest determinant in compressor choice is the thermal efficiency (assuming you are not operating at choke and surge points). If you are running a supercharger with a lot of overdrive to make more boost for your engine, changing to a larger unit will generally allow you to turn it slower to acheive the same boost pressure. Turning it faster again, as before, will produce even more boost. This is where a compressor map comes into play (ATI doesn't publish these for their ProCharger line of centrifugal superchargers, but other's due including most of the turbocharger manufacturers). Simply because two superchargers can make the same amount of boost on your engine doesn't mean they are outputing air at the same temperature (efficiency, for our sake). Generally, a larger unit will make the boost more efficiently, but it will also enter situations where it makes too much boost for your engine.

Again, this is all hard to predict as compressor maps range widely and shouldn't be guessed about. If you buy a supercharger that creates more boost at the same shaft speed as your previous unit, you will be required to change your pullies to drive the blower slower. Depending on the compressor, this can mean your boost curve is later and or taller. I think you will notice that a larger unit will start to make boost later than the smaller unit.

 

^
he sounds so smart when he says it like that.