Basic Equation for Piston Engine Power Output

Reference:
Technology of Tanks by R.M. Ogorkiewicz

or

Where:

E_P: Engine Power (Watts)
E_C: Number of Cylinders in Engine
D: Piston Diameter (meters)
L: Piston Stroke (meters)
p: Mean Effective Pressure (N/m²)
N: Number of Firing Strokes per Second.

Use the following formulas to calculate N:

2-Stroke Engines: N = (RPM / 60)

4-Stroke Engines: N = [(RPM / 60) / 2]

Unit Conversion Table

1 Bar = 100,000 N/m2
1 Watt = 0.00134102 mechanical horsepower
1 millimeter = 0.001 meter

Estimating Mean Piston Speed

Reference: Wikipedia (LINK)

Where:

MPS: Mean Piston Speed (m/sec)
S: Piston Stroke (meters)
R: Engine Rotations Per Minute (RPM)

Typical Piston Speeds

• Diesel Engine, Marine: 8.5~ m/sec
• Diesel Engine, Truck/Train: 11~ m/sec
• Diesel Engine, Automotive: 14~ m/sec
• Gasoline Engine, Average: 16~ m/sec
• Gasoline Engine, Competition: 20~ m/sec
• Gasoline Engine, Formula One: 25~ m/sec

Calculating Engine Displacement

Where:

D: Engine Displacement
B: Piston Bore Diameter
S: Piston Stroke Length
C: Number of Cylinders in Engine

NOTE: If you're entering Piston Bore/Stroke in millimeters, multiply by 0.000001 to convert from cubic millimeters to liters.

Representative Basic Data for Gasoline Engines

1938-1945 Rolls Royce Merlin / Packard V-1650 V-12

Bore/Stroke: 137.16 x 152.4mm (5.4 x 6 in)

• Merlin III: 1,030 BHP @ 3000 RPM @ 10,250 ft (6.5 lb boost): 11.37 bar (164.9 psi)
• Merlin 28 / V-1650-1: 1,240 BHP @ 2850 RPM @ 10,000 ft (9 lb boost): 14.76 bar (214 psi)
• Merlin 45: 1,515 BHP @ 3000 RPM @ 11,000 ft (16 lb boost): 16.56 bar (240.18 psi)

1962 Oldsmobile Jetfire Turbo-Rocket V-8 (turbocharged)

Bore/Stroke: 88.9 x 71.1mm (3.5 x 2.8 in)
Output: 215 BHP @ 4600 RPM
BMEP: 11.95 bar (173.32 psi)

Notes: The Jetfire was based upon the Buick “Small Block” 215 aluminum V8, which was for a time, the lightest mass production V8 in the world. This was the first mass production turbocharged consumer vehicle in the US; but it was a commercial failure past the first year, as it required a tank of methyl-alcohol to be topped up to produce maximum boost. Customers didn't know they needed to add "Turbo-Rocket Fluid"; and the engine went into "limp" mode which deactivated boost over 5 PSI when the tank was empty.

1975 Porsche 930 Turbo Carrera Flat 6 (turbocharged)

Bore/Stroke: 95 x 70.4mm
Output: 245 BHP @ 5500 RPM
BMEP: 13.56 bar (196.67 psi)

1987 Ferrari F40 Tipo F120D V-8 (turbocharged)

Bore/Stroke: 82 x 69.5mm
Output: 477 BHP @ 7000 RPM
BMEP: 20.89 bar (302.98 psi)

2013 Koenigsegg Agera S V-8 (twin turbocharged)

Bore/Stroke: 91.7 x 95.25mm
Output: 1016 BHP @ 7100 RPM
BMEP: 34.23 bar (496.46 psi)

Representative Basic Data for Diesel Engines

1939 Kharkiv V-2-34 V-12 Diesel (Naturally Aspirated)

Bore/Stroke: 150 x 183.35mm
Output: 500 BHP @ 1800 RPM
BMEP: 6.394 bar (92.73 psi)

Notes: Used in the T-34, SU-85 and SU-100.

1964 MTU MB 838 CaM 500 V-10 Diesel (Turbocharged)

Dimensions: 1552 x 1409 x 964mm (LWH), 1720 kg
Bore/Stroke: 165 x 175mm
Output: 830 BHP @ 2200 RPM
BMEP: 9.19 bar (133.28 psi)

Notes: Used in Leopard 1 and Arjun.

1978 MTU MB 873 Ka 501 V-12 Diesel (Turbocharged)

Bore/Stroke: 170 x 175mm
Output: 1500 BHP @ 2600 RPM
BMEP: 11.175 bar (162.07 psi)

Notes: Used in Leopard 2. In the original Ka 500 prototype engines, bore and stroke were 165x155mm and BMEP was 13.395; but for the production Ka 501 engines; bore was increased and BMEP decreased as turbocharger technology wasn't up to the task, due to turbo lag in the original prototypes.

1990 V8X-1500 Hyperbar Diesel (External Turbine-Powered Supercharger)

Bore/Stroke: 142 x 130mm
Output: 1500 BHP @ 2500 RPM
BMEP: 33.96 bar (492.54 psi)

Notes: This design uses a separate gas turbine engine to act as a supercharger for the diesel engine (and to act as an APU when the diesel engine is shut down. The concept was invented in the late 1970s with bench testing in the 1980s, before production engines entered service with the LeClerc in 1992.

2000 MTU MB 883 EuroPowerPack V-12 Diesel (Turbocharged)

Bore/Stroke: 144 x 140mm
Output: 1500 BHP @ 2700 RPM
BMEP: 18.59 bar (269.62 psi)

Notes: When originally installed in the early 2000s on the Merkava Mk 3; there were severe reliability problems with this engine, but it was eventually ironed out.