I just bought a Black Max 6.5hp, 2 stage, 80gal compressor.

First of all, does anyone know the cfm rating of this compressor at lower than 100psi? I can't find this information online anywhere.

It is marked 11.3cfm at 175psi and 11.9cfm at 100psi.
I want to buy a paint gun but want to make sure it will be a good match for this compressor so I need to know the cfm rating at 40 or 50psi.

How do I determine this? Can I calculate it through linear interpolation? This would put me at about 12.4cfm at 40psi. Is this correct, or is it more complicated than this?

 

It is more complicated than that, but I'd say 12.4 is not a bad estimate. I'd say a 6.5hp 2-stage will run most of the air tools you throw at it, including HVLP guns.

 

if its marked 11.3cfm at 175psi and 11.9cfm at 100psi thats .4 lower cfm at 75 less psi.
the lower the psi the more cfm it will make.
it should make 12-15 around 40 psi, plenty to run a HVLP gun!
I have a central pneumatic 30 gal 2.5 hp compressor and im running fifty ft. hose and two water traps befor my gun. But i bought a LVLP gun just to be on the safe side.
mine only make 8 cfm at 40 psi, but its plenty to spray a car and the air comressor keeps up without a problem. Just set the air compressors regulator a little higher than the gun. I spray at 16-25 psi(all coats) and set the air compressor at 40-60 psi. get a small regulator for the gun and have set 16-20psi . its really a plug and play situation

 

no choose a gun that will run with that low CFM, Iwatas are dope and they run low CFMs thas why i bought an iwata years ago and i lvoe mine