1. In a rotary piston device; a compressor comprising a three cornered piston rotatable in a two lobed chamber, an engine on each axial side of the compressor, each engine comprising a four cornered piston rotatable in a three lobed chamber, interconnected housings for the compressor and the engines in which the respective chambers are formed, end walls on the outer ends of the engine housings and other walls between the engine housings and opposite ends of the compressor housing, a shaft journalled in said walls having coplanar eccentrics for the engine pistons and an eccentric for the compressor piston displaced 180* from the engine piston eccentrics, said engine housings being displaced 180* from one another, 3:4 gearing between the engine pistons and the housings and 2:3 gearing between the compressor piston and the housing, the axis of symmetry of said compressor being displaced about 70* to 85* from the central axis of said engines, diametrally opposed air inlets in the compressor housing, fuel injection means and an exhaust port circumferentially spaced therefrom in each engine housing, a larger passage in each said other wall connecting the compressor chamber with the adjacent engine chamber in the suction region thereof which is behind the exhaust port and ahead of the fuel injection and ignition means, and a smaller passage in each said other wall connecting the compressor chamber with the adjacent engine chamber in a region behind the fuel injection and ignition means and ahead of the exhaust port, each larger passage being diametrally opposed to the smaller passage in the same said other wall and axially opposed to the smaller passage in the other said other wall, each engine housing having peripheral passages near the pertaining said smaller passage operable to connect the leading end of the last combusted space about the respective engine piston with the next preceding space about the respective engine piston at about the time the last mentioned space communicates with said exhaust port, said passages being controlled by said compressor and engine pistons so as to supply a major portion of the air compressed by said compressor to said engines as primary combustion air while applying a minor portion thereof to said engines as after combustion air.

11. A compound supercharged rotary piston engine device comprising; a pair of axially spaced rotary piston engines, a rotary piston compressor interposed between said engines, a common shaft extending axially through said engines and compressor, a dividing wall member between said compressor and each said engine and each forming the side wall of the compressor and the respective engine, said shaft having coaxial eccentrics for said engines and an eccentric displaced 180* therefrom for said compressor, said compressor forming two opposite compressor chambers, operating on each revolution of said two piston engines, to supply air to each of said two piston engines, each of said walls between said compressor and said piston engines having a pair of substantially diametrically opposite passages between the compressor and each of said piston engines, one passage in each wall leading from one compression chamber of said compressor to the combustion chamber of said piston engine and the diametrically opposite passage in said wall leading to an afterburning chamber in said piston engine, the passages in one wall being displaced 180* from the passages in the other wall and said passages to the afterburning chambers being substantially smaller than those to said combustion chambers.