What is the correct way to use engine braking?
2 Answers
The correct method for using engine braking is to ensure the engine brake is turned off before starting the vehicle. Below are relevant details about engine braking: 1. Concept: Engine braking utilizes the compression resistance generated during the engine's compression stroke, where internal friction and intake/exhaust resistance create a braking effect on the drive wheels. 2. Principle: Engine braking refers to the momentary opening of the exhaust valve near the top dead center position during the compression stroke when the accelerator is released, releasing high-pressure gas. After closing the exhaust valve, very little gas remains in the cylinder. This creates a negative pressure state in the cylinder during the explosion (expansion) stage when the piston moves downward from the top dead center.
I've been driving big trucks for decades, and engine braking has been my reliable helper when going downhill, especially when driving trucks on mountain roads. The correct method is to anticipate the slope length in advance, downshift to an appropriate low gear like third or second gear, letting the engine naturally slow down the vehicle without constantly stepping on the brakes. The engine RPM will increase, and hearing the roaring sound is normal, but don't let it stay in the redline zone for too long to avoid overheating and damaging the engine. Adjust according to road conditions—you can upshift to resume normal driving on flat sections. This method is not only safe but also prevents brake pad overheating and potential accidents. I often share this experience with friends on long-haul trips. Beginners might find it uncomfortable at first, but with a few more practices, it becomes second nature. The key is smooth transitions—avoid abrupt gear changes and maintain steady speed control.
