Abstract: A rotary piston internal combustion engine with a fission vaporizer, gasifier or carburetor means with sealing strips arranged on a mantle section of the housing, and with piston means of trochoidal construction in which the circumference of the piston means is depending on the number of cycles of the employed working method divided by a plurality of axis-near zones or lobes into arches. The piston means form within the region of each arch which during the compression and expansion cycle forms a portion of the confinement of the pertaining working chamber comprises a change-over conduit which is controlled by means of a control opening in an end face of the piston means.