1. What is the Indicated Horsepower Equation?

The Indicated Horsepower (IHP) equation calculates the theoretical power developed inside an engine cylinder based on mean effective pressure, stroke length, piston area, and engine speed. It represents the power developed by the expanding gases before accounting for mechanical losses.

2. How Does the Calculator Work?

The calculator uses the Indicated Horsepower equation:

Where:

• \( P \) — Mean effective pressure (psi)
• \( L \) — Stroke length (ft)
• \( A \) — Piston area (in²)
• \( N \) — Engine speed (RPM)
• 33000 — Conversion constant (ft-lb/min per horsepower)

Explanation: The equation calculates the power developed in the engine cylinders by considering the pressure acting on the piston throughout the stroke cycle and the engine's rotational speed.

3. Importance of IHP Calculation

Details: Indicated horsepower is crucial for engine design, performance analysis, and efficiency calculations. It helps engineers understand the actual power being developed before mechanical losses are accounted for in brake horsepower.

4. Using the Calculator

Tips: Enter mean effective pressure in psi, stroke length in feet, piston area in square inches, and engine speed in RPM. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between IHP and BHP?
A: IHP (Indicated Horsepower) is the theoretical power developed in the cylinders, while BHP (Brake Horsepower) is the actual power available at the engine output shaft after accounting for mechanical losses.

Q2: Why is the constant 33000 used?
A: 33000 ft-lb/min equals 1 horsepower (as defined by James Watt), serving as the conversion factor between mechanical work and horsepower.

Q3: How is mean effective pressure determined?
A: Mean effective pressure is typically calculated from indicator diagrams or pressure-volume curves that show the pressure variations throughout the engine cycle.

Q4: Can this calculator be used for multi-cylinder engines?
A: This calculator provides IHP per cylinder. For multi-cylinder engines, multiply the result by the number of cylinders to get total indicated horsepower.

Q5: What are typical IHP values for different engines?
A: IHP values vary widely depending on engine size, type, and application. Small automotive engines might produce 20-50 IHP per cylinder, while large marine diesel engines can produce thousands of IHP per cylinder.