Patent ID: 8171900

Claim:
An engine assembly comprising: an engine structure defining a combustion chamber and intake and exhaust ports in communication with the combustion chamber; a piston located within the combustion chamber and displaceable from a bottom dead center position to a top dead center position during an exhaust stroke and from the top dead center position to the bottom dead center position during an intake stroke immediately subsequent the exhaust stroke; a crankshaft supported by the engine structure and rotationally driven by the piston; a hydraulically actuated intake valve assembly supported by the engine structure and including an intake valve and an intake valve actuation assembly adapted to open the intake valve during the intake stroke; and a hydraulically actuated exhaust valve assembly supported by the engine structure and including an exhaust valve and an exhaust valve actuation assembly adapted to open the exhaust valve during the exhaust stroke, the exhaust valve actuation assembly operable in a first mode during an initial portion of exhaust valve closing and operable in a second mode during a final portion of exhaust valve closing, the final portion having a duration greater than a duration of the initial portion and the exhaust valve closing at a first velocity during the initial portion at least 5 times greater than a second velocity of the exhaust valve during the final portion.