Red Seal Heavy Duty Equipment Technician Practice Exam

How does a mechanical governor control engine speed?

1. By regulating air intake

2. By adjusting the fuel supply based on engine RPM and load

3. By changing the engine compression ratio

4. By altering the ignition timing

The correct answer is: By adjusting the fuel supply based on engine RPM and load

A mechanical governor controls engine speed by adjusting the fuel supply based on engine RPM and load. This mechanism typically involves a system of weights and springs that respond to engine speed. As the engine rpm increases, the centrifugal force on the weights also increases, triggering a response that adjusts the fuel supply accordingly. When the engine speed exceeds the desired threshold, the governor reduces the amount of fuel being injected or supplied to the combustion chamber, which in turn lowers the engine speed. Conversely, if the engine speed drops below the desired level due to an increase in load, the governor allows more fuel to enter the combustion chamber, increasing the engine speed back to the set point. This method of control is crucial for maintaining optimal engine performance and efficiency under varying load conditions, ensuring that the engine runs smoothly and effectively without over-revving or stalling. Other options mentioned, such as regulating air intake, changing engine compression ratios, or altering ignition timing, are not the primary methods utilized by a mechanical governor for speed control.