The final step came when steam was introduced into the cylinder to drive the piston backward as well as forward, thereby increasing the speed of the engine and cutting its fuel consumption.
最后一步是将蒸汽引入气缸，使得活塞前后推动，从而提高了发动机的速度，降低了燃料消耗。
3
Brian started the engine and pulled away slowly, but picked up speed once he entered Oakwood Drive.