当活塞再一次到达下止点时，排气门打开。

As the piston reaches BDC again the exhaust valve opens.

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当活塞再一次到达下止点时，排气门打开。

As the piston reaches BDC again, the exhaust valve opens.

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但是像进气门一样，排气门需要时间到达充分打开和关闭的位置。

But like the inlet valve, the exhaust valve needs time to reach the full-open position, it also needs time to reach the full-closed position.

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