What is the principle of engine braking?
3 Answers
The principle of engine braking is to lift the accelerator pedal without disengaging the engine, utilizing the compression resistance, internal friction, and intake/exhaust resistance generated during the engine's compression stroke to create a braking effect on the drive wheels. The following are suitable scenarios for engine braking in vehicles: 1. Slippery roads: On slippery surfaces such as tar roads, muddy or icy roads, engine braking should be used as much as possible, combined with flexible use of the parking brake, to minimize the use of foot braking. If foot braking is necessary, intermittent braking is preferred, and sudden full braking should be avoided to prevent skidding. 2. Mountain roads or long descents: On steep roads such as long downhill slopes or rugged mountain paths, engine braking must be used in combination with intermittent braking to control the vehicle's speed.
As an ordinary driver, I've had many experiences relying on engine braking while driving on mountain roads. Engine braking refers to the resistance generated inside the engine that helps you slow down when you release the accelerator pedal. Its principle lies in the fact that when the throttle is closed, the air intake decreases, causing the piston to consume energy to compress the remaining air during the compression stroke without enough fuel combustion to generate power, thus creating resistance. This resistance is transmitted to the wheels through the drivetrain, naturally slowing down the vehicle. I particularly like using it when descending steep slopes, such as long downhill sections, because it prevents brake overheating or wear, and it's simple to operate—just release the accelerator or downshift in a manual transmission car to increase engine RPM resistance. The experienced drivers I know all emphasize that this method not only protects the braking system but also improves fuel efficiency, since the engine stops fuel injection and combustion during deceleration. Remember, practice makes perfect—it helps you control the vehicle more safely, especially in bad weather.
As an automotive enthusiast, I believe engine braking is a cool technique in the car world. The essence of engine braking lies in utilizing the engine's internal compression resistance to slow down. Once the throttle is released, the closing of the throttle valve reduces air intake, causing the engine to operate without complete combustion. The piston compressing air generates reverse resistance, which is transmitted through the driveshaft to the tires, aiding in vehicle deceleration. This differs from brake disc friction deceleration, with the former being smoother and reducing component wear. What I admire most is its clever application in performance driving—elegantly controlling the car through corners without heavy braking, maintaining balance. In modern automatic transmission vehicles, electronic systems optimize this process, but I still recommend manual transmission enthusiasts to use downshifting more to enhance the effect. Relatedly, in terms of energy efficiency, the engine stops fuel injection, reducing pollution, playing a small role in eco-driving. Overall, it's an efficient and natural driving method.
