PURPOSE: To improve atomizing and mixing a fuel in a system for controlling a pumping loss due to continuity between cylinders by arranging fuel injection valves in such a way as to directly oppose working chambers so that fuel injection directions cross the axial line of a communication passage opening.

CONSTITUTION: An intermediate housing 21 is provided with a communication passage 23 for making continuous each of working chambers 5f and 5r during compression and intake strokes in a plurality of cylinders, and the communication passage 23 is provided with a control valve 24 for controlling an air flow quantity. In this case, each of front and rear direct fuel injection valves 33f and 33r is arranged in through-holes penetrating the upper walls of front and rear rotary housings 8f and 8r, in order to supply a fuel directly to each of front and rear working chambers 5f and 5r. And each of the front and rear fuel injection valves 33f and 33r is arranged at the trailing side the rotational direction of each of front and rear rotors 3f and 3r from the upward direction of the major axis of each rotor housing 8f and 8r, in order to direct fuel injection toward the opening of each of front and rear communication ports 22f and 22r.