How is bottom dead center (BDC) defined in four-stroke engines?

Bottom dead center (BDC) is defined as the lowest point of the piston within the cylinder of a four-stroke engine. This is the position where the piston has reached its furthest downward travel during its stroke. Understanding BDC is crucial for mechanics and engineers, as it plays a significant role in various engine processes, including timing of valve openings and the overall function of the combustion cycle.

When the piston is at BDC, the cylinder volume is at its maximum, and it's the point where the intake and exhaust processes are most relevant. This location helps in defining the points of compression and exhaust in the four-stroke cycle, which includes intake, compression, power, and exhaust strokes. Recognizing where BDC is relative to the piston’s movement aids in accurate timing adjustments and performance evaluations within the engine setup.