Abstract: An internal combustion engine of the rotary type having an elliptical housing within which charge-carrying pistons move. The engine includes a stationary central portion having an elliptical outer surface about which the pistons move. A pair of gate valves slide longitudinally of the central portion, dividing the working chamber into separate compression and expansion zones. A gear system maintains a particular orientation of the pistons. The valves are interconnected to open and close at the proper time to allow the pistons, with the trapped, compressed fuel-air charge carried therein, to pass from the compression zone to the expansion zone.