A reciprocating refrigerant compressor system is disclosed. The compressor system includes a cylinder, a piston disposed within the cylinder, at least one fluid passageway, and an actuator. The piston is movable between a bottom dead center (BDC) and a top dead center (TDC) position. The fluid passageway is disposed within the cylinder between the BDC and TDC position and defined by one or more apertures. The actuator is in operative communication with the aperture and is responsive to an environmental condition external to the compressor system to at least partially close the aperture.