- published: 06 Nov 2007
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Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre (TDC) to bottom dead centre (BDC). It is commonly specified in cubic centimeters (cc), litres (l), or (mainly in North America) cubic inches (CID). Engine displacement does not include the total volume of the combustion chamber.
Engine displacement is determined from the bore and stroke of an engine's cylinders. The bore is the diameter of the circular chambers cut into the cylinder block.
To simplify:
Examples: The 427 Chevy bore is 4.312 in, and the stroke is 3.65 in, therefore the displacement for this eight-cylinder engine is:
Or: (4.312 in)2 × 0.7854 × 3.65 in × 8 = 426.4 cu in
If the bore is 10 cm and the stroke is 5 cm with four cylinders, the calculation is:
In the United States, the cubic inch was the commonly used unit of measurement until the 1980s by the manufacturers to express the displacement of engines for cars, trucks, etc. (e.g., the "426" in 426 HEMI refers to 426 cubic inches displaced). It is still used for this purpose in the context of the classic-car hobby, auto racing, and so forth.[citation needed]