Usually an engine is timed so that the number 1 spark plug fires several degrees _____.
A)BTDC (before top dead center)
B)ATDC (after top dead center)
C)BBDC (before bottom dead center)
D)ABDC (after bottom dead center)

Question

Quizplus · Accepted Answer

Engines are typically timed so that the number 1 spark plug fires a few degrees before the piston reaches the top dead center (TDC) on the compression stroke, to allow the fuel-air mixture enough time to fully ignite and push the piston down with maximum efficiency. This is referred to as BTDC (before top dead center).

Usually an Engine Is Timed So That the Number 1