大多数发动机运转为四行程循环。

Most automobile engines operate on four stroke cycle.

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在四行程循环时，每凸轮必须旋转打开一阀门。

Each CAM must revolve once during the four-stroke cycle to open a valve.

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在四行程循环时，每凸轮必须旋转打开一阀门。

Each CAM must revolve once during the four-stroke cycle to open a valve.

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