ok i understand what scfm is but what i dont understand is why the scfm decreases as the psi increases? for instance i bought a compressor with the following specs 5.5 scfm @ 90 psi and 6.4 scfm @ 40 psi. i know i'm probably gonna look real dumb when someone explains it but whatever.

 

It because it is hard to force more and more air in to a given area.

Ever try blowing in to a bottle, it gets harder as you blow more in it.

Not an engineer but I think this is why

 

PSI is a measure of restriction, more restriction, less flow.

 

so if i were to upgrade my regulater to say 3/8" from 1/4" it would increase the scfm delivered?

 

Potentially. Still depends on what tool you are using.