The exact position in an internal combustion engine where a piston reaches the absolute bottom of its stroke, furthest from the cylinder head. At this point, the connecting rod and crankshaft throw are perfectly aligned, and cylinder volume is at its maximum before the compression or exhaust stroke begins.
Heard on the job
Rotate the crank until cylinder four reaches bottom dead center so we can inspect the cylinder walls.
Also heard as
- BDC
Do not mix it up with
- Top dead center: TDC is the highest point of piston travel, whereas BDC is the lowest.
Related terms
Top dead center
The exact point in engine rotation where a piston reaches its highest position in the cylinder.
Bottom-end
The lower section of an engine block containing the crankshaft, connecting rods, and main bearings.
Compression ratio
The mathematical ratio of cylinder volume at the bottom of the piston stroke compared to the top.