Abstract: A rotary internal combustion engine that includes a housing that defines an elliptical cavity in which a rotor is disposed. The rotor slidably supports a number of circumferentially spaced, radially disposed blades, with each pair of blades defining a chamber therebetween. The rotor is so rotatably supported in the cavity that the ratio of the intake chamber volume may be adjusted so that there is a minimum residual pressure on exhaust gases and the efficiency of the engine is increased as a result thereof.