What is top dead center on compression stroke a Z24i engine?

Top Dead Center (TDC) on the compression stroke of a Z24i engine (or any engine, for that matter) is the point where the piston in a cylinder is at its highest point *during the compression stroke*. It's the instant before the piston begins its downward stroke to initiate the power stroke.

It's important to note that TDC occurs twice per engine revolution for each cylinder—once on the compression stroke and once on the exhaust stroke. To be precise, we're talking about TDC on the compression stroke in this context. This is a crucial point for ignition timing, as the spark plug needs to fire very near this point for optimal combustion.