Computing Piston Engine Power Output
EnginePower = (n * ( π / 4 ) * D2 * L) * p * N
n (Number of Cylinders)
D (Piston Diameter, Meters)
L (Piston Stroke, Meters)
p (Mean Effective Pressure, N/m2)
N (number of firing strokes per second, which equals the number of revolutions per second in the case of two-stroke engines and half the number of revolutions per second in the case of four stroke engines.)
Note: 10,000 N/m2 equals 1 Bar.
Technology of Tanks by R.M. Ogorkiewicz.