Question

The mechanical efficiency of an engine is expressed as

• A. BHP/IHP $\times$ 100
• B. IHP/BHP $\times$ 100
• C. (IHP-BHP)/IHP $\times$ 100
• D. (BHP-IHP)/BHP $\times$ 100

Hint:

Output Input. BHP is what you get (output); IHP is what the fuel gave (input).

Answer 1

The Correct Option is A

Step 1: Concept Efficiency is the ratio of useful output to the total input.

Step 2: Meaning Indicated Horsepower (IHP) is the total power produced inside the cylinder, and Brake Horsepower (BHP) is the actual power available at the crankshaft.

Step 3: Analysis BHP is always less than IHP due to frictional losses within the engine ($FHP = IHP - BHP$). Mechanical efficiency measures how much of the generated power is successfully transmitted to the output.

Step 4: Conclusion Mechanical Efficiency = $\frac{BHP}{IHP} \times 100$.
Final Answer: (A)