Engine including system and method for reducing oil pull-over in combustion chamber

An engine assembly comprising:

• an engine structure defining a combustion chamber and an intake port and an exhaust port in communication with the combustion chamber;
• a piston located within the combustion chamber and reciprocally displaceable from a top dead center position to a bottom dead center position during an intake stroke and displaceable from the bottom dead center position to the top dead center position during a compression stroke immediately subsequent the intake stroke;
• an intake valve supported by the engine structure and selectively opening and closing the intake port;
• an exhaust valve supported by the engine structure and selectively opening and closing the exhaust port;
• an intake valve actuation assembly engaged with the intake valve and operable in first and second modes, the intake valve actuation assembly operated in the first mode when fuel is provided to the combustion chamber and operated in the second mode when fuel is cutoff from the combustion chamber while the piston reciprocates between the top dead center position and the bottom dead center position, the first mode providing a first opening duration of the intake valve during one of the intake stroke and the compression stroke and the second mode providing a second opening duration of the intake valve during the one of the intake stroke and the compression stroke that is different than the first opening duration to reduce vacuum in the combustion chamber;
• and
• an exhaust valve actuation assembly engaged with the exhaust valve and operable in third and fourth modes, the exhaust valve actuation assembly operated in the third mode when fuel is provided to the combustion chamber and operated in the fourth mode when fuel is cutoff from the combustion chamber while the piston reciprocates between the top dead center position and the bottom dead center position, the third mode providing a third opening duration of the exhaust valve during one of the intake stroke and the compression stroke and the fourth mode providing a fourth opening duration of the exhaust valve during the one of the intake stroke and the compression stroke that is different than the third opening duration to reduce vacuum in the combustion chamber, wherein:
• the first and second opening durations occur during the intake stroke and the second opening duration is greater than the first opening duration, and
• the third and fourth opening durations occur during the compression stroke and the third opening duration is greater than the fourth opening duration.

A method comprising:

• reciprocating a piston located within a combustion chamber of an engine structure from a top dead center position to a bottom dead center position during an intake stroke and from the bottom dead center position to the top dead center position during a compression stroke immediately subsequent the intake stroke;
• opening a first valve to provide communication between the combustion chamber and a first port of the engine structure for a first opening duration during one of the intake stroke and the compression stroke when fuel is provided to the combustion chamber while the piston is reciprocating;
• and
• opening the first valve to provide communication between the combustion chamber and the first port for a second opening duration during the one of the intake stroke and the compression stroke when fuel is cutoff from the combustion chamber while the piston is reciprocating, the second opening duration being different than the first opening duration to reduce vacuum in the combustion chamber.