Abstract: An internal combustion engine comprises a housing defining an air inlet opening, a first set of rotatably mounted interengaging air intake and compression rotor wheels, and an air passageway connecting said air intake and compression rotor wheels to a second set of rotatably mounted interengaging compression and metering rotor wheels. The compression and metering rotor wheels deliver air to a combustion chamber defined by the housing. Fuel is injected into the combustion chamber and ignited. The combustion chamber communicates with a third set of rotatably mounted interengaging output rotor wheels which are driven by the exhaust gases and are connected to drive the aforementioned rotor wheels. The working area of the output rotor wheels is greater than the working area of the compression and metering rotor wheels, wherein the combustion gases always drive the output rotor wheels.