Abstract: A system and method for controlling the displacement of a variable displacement compressor by feeding back crankcase pressure as part of a control scheme is disclosed.

Abstract: A variable control valve 10 for a gas compression system is disclosed for a gas compressor 100 with a piston 116 having a variable displacement within a compression chamber 114 of the gas compressor. A pressure within a crankcase chamber 118 of the gas compressor acts upon the piston A diaphragm 36 within the control valve, controls a flow of high and low pressure gas into and out of the pressure chamber, thus controlling the displacement of the piston. The diaphragm is acted upon by a predetermined reference pressure within a reference chamber 90 of the control valve. The predetermined reference pressure within the reference chamber is created by a flow into and out of the reference chamber of the high and low pressure gas. The predetermined reference pressure can be changed in order to optimize compressor output. This flow is controlled by reference chamber valve means (88, 86) operably coupled to the reference chamber, the reference chamber valve means being responsive to electrical signals.