Originally posted by Munson:
Ok, Jim, I agree I can't argue with a gauge.
Anyone have any theories here? A supercharger will have its flow rate fixed by it impeller speed, ie by engine speed. So, new or old exhaust, flow rate (cfm) will be constant for a given engine speed.
How could intake manifold pressure increase under constant flow rate conditions?
-Kurt
CFM is not constant because you changed the flow out of the motor by changing the exhaust restriction. This changes the efficiency of the entire system. The higher boost of the new system comes from more restriction, but would also change the scale on the SC/engine efficiency. The more open Magnaflow system he removed must have been out of his efficiency range if he truly is making more power now because the boost went up, not down.
Only if you're maxing out the SC flow rating are you going to see a constant anything at any RPM. Even still, you change one part of the system to flow more or less and the air flow will change one way or the other because you changed the efficiency...
