Engine displacement, expressed in cubic inches (or cubic centimeters), represents the total swept volume of all the cylinders within an engine. It’s calculated by multiplying the cylinder bore area (r where ‘r’ is the radius of the cylinder bore) by the stroke length (the distance the piston travels in the cylinder) and then multiplying that result by the number of cylinders in the engine. For example, a single-cylinder engine with a 4-inch bore and a 3-inch stroke has a displacement of approximately 37.7 cubic inches.
This measurement provides a valuable indicator of an engine’s potential power output. Generally, larger displacements correlate with greater power potential, although factors like engine design, aspiration, and tuning significantly influence actual performance. Historically, displacement has served as a key criterion for classifying vehicles and engines, influencing everything from taxation and insurance rates to racing regulations. Understanding this metric allows for informed comparisons between engines and provides insight into an engine’s characteristics.