BTDC Before Top Dead Center的用法和樣例：
例句
- The clock began to whirr before striking the hour.
鐘在打點(diǎn)前先嘎啦嘎啦地響起來(lái)。 - The spark is therefore timed to occur before the piston reaches top dead center, otherwise maximum pressure would not be reached in time.
因而，在活塞到達上死點(diǎn)前，火花便會(huì )發(fā)生，否則就不可能適時(shí)達到最高的壓力。
