Originally Posted by beertracker
I am getting ready to paint my car and need to know what size air compressor in terms of CFM and pressure does it take to shoot paint?
You need to size the gun to the job then the compressor to the gun. This is where a home paint job gets expensive.
You'll have to shop and shop hard looking at specifications. They like to sell compressors by horsepower. This counts but is a huge range of efficiencies between what the motor is rated at in power and what the compressor delivers in pressure and CFM. CFM and pressure is what counts not motor power. In general as pressure goes down in the specification the available CFM goes up.
Spary guns vary all over as well. One usually assumes that HVLP guns use less air CFM and pressure than the older syphon guns, this isn't exact in all cases. The bottom end DeVilbis Starting Line model needs 13 CFM at 30 PSI. step up a level in quality and the gun needs about 13 CFM at 20 PSI.
Very inexpensive guns that look the same as the DeVilibus can use 4 to 7 CFM at 30 to 50 psi, these are fine but deliver a smaller pattern. however you've got to watch out there are some inexpensive guns that chew up a lot of CFM and pressure while still advertised as HVLP guns, imagine 17 CFM at 50 to 70 PSI in one example.
The compressor needs to be able to continously support the pressure and CFM requirement without thermally cutting out. These also need wiring to support their cycle, voltage and amperage requirements. 110 VAC motors will be smaller and power hungry, 220-240 will be a bit easier on the amperage which sizes the wire and breakers. Home and most shops ony use single phase. Three phase is very expensive to have wired as are converters to make 3 phase. Typically 2 horsepower can support less than 10 CFM and less than 50 PSI for painting with about 5 horsepower to support 13-14 CFM at about 40 PSI. This is just general, you've got to shop to the required numbers of what the gun needs. As with most everything a larger compressor than needed is easier to live with than too small for the job.