What is the working principle of a four-stroke gasoline engine?
2 Answers
The working principle of a four-stroke gasoline engine is relatively simple. This type of engine operates through four strokes: intake stroke, compression stroke, power stroke, and exhaust stroke. During the intake stroke, the intake valve opens, and the piston moves downward to draw in air or a combustible air-fuel mixture. In the compression stroke, both the intake and exhaust valves close, and the piston moves upward to compress the combustible mixture. During the power stroke, the spark plug ignites the compressed mixture, causing it to burn and push the piston downward. In the exhaust stroke, the exhaust valve opens, and the piston moves upward to expel the combustion gases. Intake methods of four-stroke gasoline engines: Four-stroke gasoline engines can be naturally aspirated, turbocharged, or supercharged. While these three types differ in their intake methods, their fundamental four-stroke working principles remain the same. Working principle of four-stroke gasoline engines: In actual usage, conditions are more complex, so most engines are also equipped with variable valve lift systems and variable valve timing systems to adjust engine performance under different operating conditions.
For someone like me who has long been involved in car maintenance, the working principle of a four-stroke gasoline engine is actually quite intuitive. The piston moves up and down in the cylinder, completing a cycle in four steps: The first is the intake stroke, where the intake valve opens as the piston descends, drawing in a mixture of gasoline and air; the second is the compression stroke, where the piston rises to compress the mixture with the valves closed; the third is the expansion stroke, also known as the power stroke, where the spark plug ignites the compressed mixture, causing an explosion that rapidly drives the piston downward, generating thrust; finally, the exhaust stroke occurs as the piston rises again with the exhaust valve open to expel the waste gases. These four actions connect and repeat in a cycle, converting the motion through the crankshaft into wheel power. The entire process is quiet, efficient, and more environmentally friendly and fuel-efficient than older two-stroke engines. When driving, avoid frequent sudden acceleration, as it can easily lead to carbon buildup clogging the spark plugs and causing unstable ignition. Regular oil changes and maintenance can extend the engine's lifespan, keeping the car running smoothly for many years.
