PURPOSE: To raise the charging efficiency of a two-cylinder rotary piston engine and to thereby increase the engine output effectively, by providing a main port which is opened always and an auxiliary port which is opened with some delay to the main port.

CONSTITUTION: A high-load intake port 4 consists of a main port 4a the opening area of which is fixed and an auxiliary port 4b the opening area of which is variable. The opening period of the port 4 is set at a specific range according to the opening and closing conditions of a control valve 16 and the turning angle of an eccentric shaft 8. With such an arrangement, supercharging effect can be obtained by the interference of exhaust gas between the two cylinders and natural pulsation of intake air of each cylinder. By thus raising the charging efficiency of the engine at the time of its high-speed and medium-speed operation, it is enabled to increase the engine output effectively.