What is the working principle of a four-stroke internal combustion engine?

[JasonRose]

The working principle of a four-stroke internal combustion engine is as follows: The working process of a four-stroke internal combustion engine consists of four strokes: intake, compression, power, and exhaust. These four strokes form one working cycle. During one working cycle, the piston reciprocates twice, and the crankshaft rotates two turns. Among the four strokes, only the power stroke generates external work, while the other three strokes are completed by the inertia of the flywheel. Here are some additional details: 1. Intake stroke: The intake valve opens, the exhaust valve closes, the piston moves downward, and a mixture of gasoline and air enters the cylinder. 2. Compression stroke: Both the intake and exhaust valves are closed, the piston moves upward, and the fuel mixture is compressed. 3. Power stroke: At the end of the compression stroke, the spark plug generates an electric spark, causing the fuel to burn violently and produce high-temperature, high-pressure gas. This high-temperature, high-pressure gas pushes the piston downward, driving the crankshaft to rotate and perform external work. 4. Exhaust stroke: The intake valve closes, the exhaust valve opens, the piston moves upward, and the exhaust gas is expelled from the cylinder.

[VanWalter]

The working principle of a four-stroke internal combustion engine is quite simple, divided into four steps: First is the intake stroke, where the piston moves downward, drawing in a mixture of air and fuel; next is the compression stroke, where the piston moves upward, compressing the mixture tightly and heating it up; then comes the power stroke, where the spark plug ignites the mixture, causing an explosion that pushes the piston downward—this is the real source of power; finally, the exhaust stroke occurs, with the piston sliding back up to expel the burnt exhaust gases. This cycle repeats with every rotation, keeping the engine running continuously. As a guy who's been driving for years, I always emphasize that this rhythm must be precise; otherwise, the engine may shake or fuel consumption may increase. During maintenance, it's common to check the spark plugs and intake pipes to avoid blockages that could affect air intake, ensuring the engine lasts longer and runs more efficiently.

[SanJordan]

As an experienced daily driver, I'm quite familiar with the four strokes of an engine: first, the piston descends to draw in the air-fuel mixture; second, it compresses them to the limit; third, ignition occurs, pushing the piston down and giving the car power; fourth, exhaust gases are expelled to keep things clean. This cycle may seem simple, but it's what actually drives the wheels forward. I particularly enjoy the feeling of acceleration, especially that kick-in-the-back sensation during sudden acceleration, though it's important to watch the engine temperature to prevent overheating. By the way, let's talk about idle issues—if the air-fuel mixture isn't properly balanced, the engine can stall easily. That's why it's essential to clean the throttle body regularly during maintenance to ensure smooth operation.

[Byron]

The four-stroke internal combustion engine operates in four stages: intake of the air-fuel mixture, compression to prepare for ignition, combustion to drive the piston, and finally exhaust to expel gases. This model is quite efficient, with the key being an appropriate compression ratio—too high may cause knocking, while too low wastes energy. As a tech enthusiast, I find this mechanism classic, and many modern engines now use ECUs to optimize ignition timing for smoother combustion. For daily driving, it's recommended to change the engine oil regularly to ensure smooth piston movement.