Engine displacement and compression calculator
Displacement is the swept volume of one cylinder times the number of cylinders. Compression ratio adds the combustion chamber.
Displacement
1998.2cc
- In litres
- 1.9982
- In cubic inches
- 121.94
- Swept volume per cylinder
- 499.56 cc
- Compression ratio
- 10.991
- Bore to stroke ratio
- 1.0000 Square
- Piston crown area
- 5809 mm2
- Mean piston speed at 6000 rpm Above about 20 m/s is racing territory.
- 17.20 m/s
Show the working
- Bore = 86
- Stroke = 86
- Cylinders = 4
- Combustion chamber volume = 50
- Swept volume per cylinder = pi * (86/20)^2 * (86/10) = 499.557
- Displacement = 499.557 * 4 = 1998.23
- In litres = 1998.23 / 1000 = 1.998 23
- In cubic inches = 1998.23 / 16.387064 = 121.939
- Compression ratio = 50 > 0 ? (499.557 + 50) / 50 : 0 = 10.9911
- Bore to stroke ratio = 86 > 0 ? 86 / 86 : 0 = 1
- Piston crown area = pi * (86/2)^2 = 5808.8
- Mean piston speed at 6000 rpm = 86 / 1000 * 2 * 6000 / 60 = 17.2
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- swept volume = pi (bore/2)^2 x stroke
- compression ratio = (swept + chamber) / chamber
Real compression ratio also depends on gasket thickness, piston dish and deck clearance; this is the simple two-volume version.