US Patent 7997237 Multi-stroke internal combustion engine

An example engine method utilizes a first intake valve actuated by a first camshaft once every four piston strokes and a second intake valve actuated by a second camshaft once every four piston strokes, but out of phase with the first intake valve actuation, to provide two-stroke operation. Transitions between two and four stroke operation are provided by deactivation and activation of the second intake valve. In this way, the engine may be selectively operated in a two stroke cycle or a four stroke cycle by activating or deactivating one of the intake valves while another of the intake valves continues to operate.