This may be a little off topic but I hope it will make sense at the end.
You guys are thinking of small coolant compressors with small outputs, why not go bigger. Without going to far off subject I will tell you the off road industry have been using modified AC pumps for main air compressors. Still capable of 500PSI+ with the volume of a shop compressor.
The best ones are made by "York" they are oil lubricated, use a simple V belt and can be bought cheep. Add a old lawn mower engine and you have a compleat portable compressor that at low pressers can run a drill and still fill a 500 psi tank.
I am at work still so I can't give anymore info just search the following terms. OBA, on board air, York AC compressor, ect.
I will post up latter with more info and I can get some pictures. I have the big daddy of them all a 10 CC duel piston sitting in the garage next to a lawnmower engine.
