Lesson 1/Learning Event 1
FIGURE 10. PISTON POSITIONS.
TDC and BDC. When you hear someone say the letters TDC or BDC, they are talking about the position of
the piston in the cylinder. TDC is just a short way of saying top dead center, and BDC is saying bottom dead
center. At TDC the crankshaft throw is pointed straight up, and the piston is at its highest point of travel in
the cylinder (top). The crankshaft and piston positions are just the opposite at BDC.