A two stroke internal combustion engine with variable compression ratio

A two-stroke internal combustion engine comprising at least one piston 19 reciprocally within a cylinder 20, an exhaust port 23 allowing communication of the cylinder with an exhaust passage 24, where the port is opened and closed by the piston during the reciprocal motion thereof, a moveable shutter mechanism 1 for varying the effective area of the exhaust port, where the shutter mechanism varies the effective area cyclically in a timed relationship to the reciprocal motion of the piston within the cylinder, a compression ratio variation mechanism for varying a compression ratio of the cylinder, sensors for measuring one or more operating characteristics of the engine and for generating signals corresponding thereto, and a control unit which processes the signals generated by the sensor means to control the motion of the shutter mechanism and the compression ratio variation mechanism to vary the compression ratio of the cylinder; wherein the engine can operate with a compression ratio in the range 32:1 to 50:1.