Practice question

How does diesel engine rotational speed (RPM) affect the braking efficiency of an engine compression release brake (如皆可博 Jacobs 缸内制动) or exhaust brake on downhill grades?

  1. Higher engine RPM (within safe manufacturer governor limits, e.g., 1,800–2,100 RPM) produces significantly greater retarding horsepower than low RPM
  2. Engine retarding horsepower is highest at low idle (600 RPM) and drops to zero at 1,800 RPM
  3. Engine RPM has no physical relationship to retarding power, which depends only on ambient temperature
  4. Exhaust brakes only function when the engine is turned completely off

Answer: A — Higher engine RPM (within safe manufacturer governor limits, e.g., 1,800–2,100 RPM) produces significantly greater retarding horsepower than low RPM

The correct answer is shown above. Try the full quiz for additional practice.

Practice more: China Truck Subject 4 Practice Questions - China Commercial Vehicle Driving Test Subject 4 Safe and Civilized Driving (大型客货车科目四安全文明驾驶常识) Exam →