BTDC Before Top Dead Center

• 在上止点前

BTDC Before Top Dead Center的用法和样例：

例句

1. The clock began to whirr before striking the hour.
   钟在打点前先嘎啦嘎啦地响起来。
2. 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，在活塞到达上死点前，火花便会发生，否则就不可能适时达到最高的压力。