Abstract: An internal combustion engine is provided that has a stationary cylinder block in which cylinders contain reciprocating pistons that are sequentially actuated to impart torque to a revolving rotor. A unique rotor is provided that includes a cam surface that controls the reciprocation of the pistons through followers. Ports in the rotor conduct working fluids to and from the cylinders. An exhaust blow-down nozzle is provided in the rotor that transforms kinetic energy in the exhaust into additional torque. There is no residual gas fraction present during combustion and the engine operates with true constant volume combustion.