Internal combustion engine comprising means for controlling the axial extent of an exhaust port in a cylinder

In a two-stroke cycle internal combustion engine comprising

• an exhaust system,
• cylinder structure having an inside peripheral surface which defines a cylinder bore and is formed with an exhaust port, which has an axial extent along the axis of said cylinder bore and communicates with said exhaust system,
• a piston, which is axially reciprocable in said cylinder bore and adapted to open and close said port,
• a restricting member, which is mounted in said cylinder structure adjacent to said port and adjustable between a full-flow position, in which said restricting member exposes said exhaust port throughout its axial extent, and a restricting position, in which said restricting member restricts the axial extent of said exhaust port, and
• a positioning drive operatively connected to said restricting member and operable to adjust said restricting member between said full-flow and restricting positions,
• said engine being operable to develop an exhaust gas pressure in said exhaust gas system,
• the improvement residing in that
• said positioning drive is adapted to be controlled in dependence on the exhaust gas pressure in said exhaust gas system.