SCFM/PSI Relationshipby Joe I'm shopping for an air compressor and see 40 psi and 90 psi as a common point of reference for SCFM. Bill answers... Hi Joe: Sigh! I wish the compressor manufacturers would recognize that air, coming out of a compressor discharge after being compressed, is no longer SCFM, but rather, CFM. That's my opinion, and I'll stick by it. Here's information about what a SCFM is! Now, to your question. Your compressor has an electric motor, and the process of compressing air converts the electrical energy consumed by the motor into stored energy in the form of compressed air in the compressor receiver. Since it's easier to compress air to 40 PSI than to 90 PSI, then the compressor, using the same amount of electrical energy, can produce more flow (in CFM, not SCFM) at the lower pressure than the high. Energy cannot be created nor destroyed. It can only be changed from one type to another form of energy. Since the electric compressor motor is already running at top speed, it's using all of the available energy it has, and since it's more work to compress air to 90 PSI than 40 PSI, you get less flow at the higher pressure. If you were able to get more flow at 90 PSI than at 40 PSI, somehow the compressor would have to manufacture more energy than was available from the existing motor, and if you could make that happen, you'll be a very rich person! Make sense? I hope so. Nice hearing from you. Bill
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