Abstract: A device carrying air reservoir means and a compressor is adapted to be mounted on a conventional four cycle internal combustion engine to convert it to operation by air pressure. The device has air pressure reservoirs, valves and conduits for delivering air pressure to the cylinders of an engine in timed sequence. After each power stroke air is exhausted to the inlet of a compressor carried by the device which delivers the compressed exhaust air back to the reservoirs and in doing so adds to the exhaust air energy substantially equal to the useful work output of the engine.

Abstract: An engine of the reciprocating piston type is provided in which the motive power for power generating pistons is compressed air stored in compartments forming part of the engine which are replenished with compressed air by a piston operating in a cylinder which receives exhaust air from the power cylinders, supplemented by air provided by an externally powered compressor. There are two power pistons operating in unison between top and bottom dead center, but with their power and exhaust strokes alternating. Spent air is exhausted through timing valves to the replenishing cylinder and compressed with the supplemental air into a first chamber from which the compressed air flows through check valves to the compartments. Engine speed is controlled by a throttle valve regulating the flow of air from the first chamber to atmosphere.