| 摘要 |
An engine assembly may include an engine structure defining a first intake port in communication with a combustion chamber, an intake manifold, a vacuum actuated mechanism, a first intake valve, and a valve actuation assembly. The vacuum actuated mechanism may include a vacuum chamber in communication with the intake manifold. The first intake valve may open and close the first intake port. The valve actuation assembly may be engaged with the first intake valve and may be operated in first and second modes. The first mode may provide a first opening duration of the first intake valve during one of an intake stroke and a compression stroke of a piston located in the combustion chamber. The second mode may provide a second opening duration of the first intake valve that is different than the first opening duration, providing reduced intake manifold pressure.
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