Abstract: A rotary engine having a rotor housing with a bisected, offset elliptical interior wall and a rotor member disposed therein. Four rotor vanes reciprocate radially from within said rotor wherein the opposing vanes perform the same function simultaneously as they pass through the cycle. The rotor vanes are forced out of the rotor by a pressurized oxygen/fuel mixture entering behind the vanes through the ports of the ported side plate. The rotation of the rotor urges the vanes back into the rotor due to the narrowing elliptical walls of the housing thereby forcing the oxygen/fuel mixture through the transfer ports and one-way check valve and into the combustion chamber where it is compressed and ignited.