Red Seal Heavy Duty Equipment Technician Practice Exam

Which measurements are used to determine the engine’s horsepower?

1. Engine torque and cylinder pressure

2. Engine RPM and torque

3. Fuel flow rate and air density

4. Exhaust temperature and fuel efficiency

The correct answer is: Engine RPM and torque

Engine horsepower is calculated using the relationship between engine RPM (revolutions per minute) and torque. The formula for calculating horsepower is derived from the concept of work done over time, with horsepower being a measure of power, which is the rate at which work is performed. Specifically, horsepower can be calculated using the formula: Horsepower = (Torque × RPM) / 5,252 In this equation, torque is expressed in foot-pounds and RPM represents the engine speed. This demonstrates that higher RPM or higher torque directly translates to increased horsepower. The other options do not accurately reflect the standard calculations for horsepower. While engine torque is involved in the calculation, factors like cylinder pressure, fuel flow rate, air density, exhaust temperature, and fuel efficiency do not directly contribute to the horsepower calculation in the same manner. Therefore, understanding the relationship between torque and engine speed (RPM) is crucial for determining the engine’s horsepower effectively.