Abstract: A rotary engine having two opposite rotating rotors forming a substantial part of a toroidal chamber such that the toriodal chamber is parted into two lateral parts formed by an outer rotor having a disk-like part forming one side of the chamber and a lateral flange forming the outside and an inner rotor having a disk like part and a center hub forming the inside of the chamber, the rotors each having half cylinder shaped piston pockets which rotatably receive half cylinder shaped pistons that are rotatably supported on their rotors. The pistons are rotated in the same direction with respect to each other and are carried around the toroidal chamber by the rotors as they rotate in opposite directions on the rotors forming an expansion chamber between the pistons as they rotate. The pistons are rotated by stationary gears and the pistons pass each other in the expansion chamber twice on each rotation of the engine. The axis of rotation of the pistons is parallel to the axis of rotation of the rotors.