Last step, exhaust valve opens, piston travels up, it forces that spent burnt gases out your exhaust pipe, out into the atmosphere.

最后一步，排气阀打开，活塞向上移动，它迫使燃烧过的气体从排气管向下进入大气。

Then the intake valve closes, and an exhaust valve opens.

然后进气阀关闭，打开 排气阀。