US Patent 9506407 Engine having active exhaust valve position control system and method

A system and method selectively reduce power of an engine having at least one piston movable in a cylinder and an exhaust port includes providing an exhaust valve in communication with the exhaust port of the engine. The exhaust valve has an adjustable position to change an effective size of the exhaust port. The system and method also include sensing a condition likely to cause damage to the piston of the engine and adjusting a position of the exhaust valve to reduce a size of the exhaust port in response to sensing the condition likely to cause damage to the piston of the engine, thereby limiting power of the engine.