How to Calculate Engine Displacement?
2 Answers
Displacement = π × radius² × height 3.1416159 × piston radius (mm) × piston radius (mm) × stroke (mm) × number of cylinders. Cylinder displacement is only an approximate value and is generally higher than the labeled value. Bore refers to the diameter, and the unit is usually millimeters.
I've been repairing cars for twenty years, and calculating engine displacement is actually quite simple. Displacement is the sum of the working volumes of all cylinders. The volume of a single cylinder equals the volume swept by the piston from top dead center to bottom dead center. The formula is: divide the bore diameter by 2 to get the radius, multiply π by the radius squared, then multiply by the stroke to calculate the single-cylinder displacement, and finally multiply by the total number of cylinders. For example, a 4-cylinder engine with an 80mm bore and 90mm stroke would have a displacement of about 1.8 liters. Displacement directly affects power output—large-displacement cars accelerate fiercely but have high fuel consumption, while small-displacement cars are fuel-efficient but may struggle to power large vehicles. Nowadays, many cars use turbocharging, allowing small-displacement engines to produce high horsepower, but the fundamental calculation principles remain unchanged.
