Enter your engine's Piston Bore Diameter, Stroke Length, Number of Cylinders, RPM, and Mean Effective Pressure (in your choice of pressure unit) to calculate your engine's Indicated Horsepower — plus Piston Area, Stroke Rate, and Engine Displacement as bonus outputs.
Indicated Horsepower
--
Piston Area
--
Stroke Rate
--
Engine Displacement
--
Indicated horsepower is the theoretical power produced in a reciprocating engine if it were completely frictionless in converting the expanding gas energy in the cylinders. It represents the ideal power output based on cylinder pressure and engine geometry.
Indicated HP is the theoretical power calculated from cylinder pressure data, while brake horsepower is the actual power measured at the engine's output shaft. Brake HP is always lower due to friction losses, pumping losses, and other inefficiencies.
Mean effective pressure is the average pressure acting on the piston during the power stroke. It's calculated from the pressure-volume diagram of the engine cycle and represents the effective pressure that produces work.
In a four-stroke engine, there is only one power stroke for every two revolutions of the crankshaft. Therefore, the effective stroke rate for power production is half the engine RPM.
Indicated HP depends on piston area, stroke length, number of cylinders, engine RPM, and mean effective pressure. Larger displacement, higher RPM, and greater cylinder pressure all increase indicated horsepower.
This calculation provides a theoretical estimate based on ideal conditions. Actual engine performance will be lower due to friction, heat losses, incomplete combustion, and other real-world factors not accounted for in the indicated HP formula.