Abstract: A rotary engine has a plurality of pistons rigidly connected as a single assembly, which pistons advance in a substantially toroidal chamber continuously along an annular path. Included in each of at least one firing position along this path is an inwardly projecting valve defining combustion zones within the chamber, and preventing communication between adjacent combustion zones. Also included in the firing positions are at least one exhaust port, an inlet port and valve, and a spark plug. Power may be taken from a central shaft along the axis of rotation of the piston assembly. The floor of the chamber comprises a movable wall which rises with increasing rotational speed to decrease effective engine displacement.