Definitions for "Top Dead Center"
Keywords:  piston, tdc, stroke, atcd, viscon
When the piston of an engine reaches the top of its stroke it is said to be at top dead center. This piston position happens to be the point at which the air/fuel mixture is most compressed. In most engines, depending on their RPM, the spark plug will fire a few degrees before the top dead center in order to start the burning process before the down or power stroke. One of the great benefits of Viscon is its ability to control the propagation of a flame emanating for a spark plug. By reducing the number of very small droplets of fuel, Viscon promotes a more even burning flame, which makes ignition before top dead center work more efficiently.
or TDC: The position of the piston in the cylinder bore at its uppermost point in the stroke. Occurs twice within the full cycle of a four-stroke engine; at the start of the intake stroke and 360 degrees later at the end of the compression stroke.
Abbreviated as "TDC", the position a piston reaches when its upward travel ends and pauses momentarily as the connecting rod pivots beneath it. Used in setting engine timing.