What is the working cycle of a gasoline engine?

[StSkylar]

The working cycle process of a gasoline engine consists of four strokes: intake, compression, combustion expansion, and exhaust. Below is the relevant introduction: Intake stroke: At this time, the piston is driven by the crankshaft to move from the top dead center to the bottom dead center, while the intake valve opens and the exhaust valve closes. When the piston moves from the top dead center to the bottom dead center, the volume above the piston increases, the gas pressure inside the cylinder decreases, creating a certain degree of vacuum. Since the intake valve is open, the cylinder is connected to the intake pipe, and the air-fuel mixture is drawn into the cylinder. When the piston reaches the bottom dead center, the cylinder is filled with fresh air-fuel mixture and the exhaust gases left from the previous working cycle. Compression stroke: The piston moves from the bottom dead center to the top dead center, with both the intake and exhaust valves closed. The crankshaft rotates under the inertia force of the flywheel, pushing the piston upward through the connecting rod, gradually reducing the gas volume inside the cylinder. The gas is compressed, and the pressure and temperature of the air-fuel mixture inside the cylinder increase accordingly.

[Thomas]

Hey, this question is actually quite interesting, just like when I first started learning to drive and was curious about engines. The working cycle of a gasoline engine basically consists of four stages: intake, compression, combustion, and exhaust. In the first step, when the engine intakes air, the piston moves downward, and the valve opens to suck in a mixture of air and gasoline. The second step is compression, where the piston moves upward, compressing the mixture, making it smaller and heating it up. The third step is combustion, where the spark plug ignites the mixture, causing an explosion that pushes the piston downward, generating power to drive the wheels. The fourth step is exhaust, where the piston rises again, opening the exhaust valve to expel the waste gases. Then this cycle repeats continuously, and the car starts moving. It differs from a diesel engine, which requires compressing air before injecting fuel for ignition. I often remind my friends that a well-maintained engine ensures a smooth cycle—don’t save on fuel costs by going to small, unreliable repair shops. Otherwise, poor compression can lead to insufficient power or high fuel consumption, making long-distance drives a nerve-wracking experience.

[JeffreyDella]

As a seasoned car enthusiast, I'm quite familiar with the gasoline engine working cycle—it's a four-stroke process: intake, compression, power, and exhaust. During the intake stroke, the intake valve opens and the piston moves downward to draw in the air-fuel mixture; in the compression stroke, the valves close and the piston moves upward to compress the mixture, raising its temperature; then the spark plug ignites, causing the mixture to combust and push the piston downward to generate power; finally, the exhaust valve opens, and the piston moves upward to expel the exhaust gases. This cycle is highly efficient—Nikolaus Otto invented it in 1876, and it's more fuel-efficient than steam engines and two-stroke engines. When modifying my car, I adjust the valve timing to optimize the cycle, such as increasing the compression ratio for more power; but don't modify recklessly—if the spark plugs are dirty and ignition timing is off, the cycle gets disrupted, affecting acceleration response. In daily driving, this cycle determines fuel efficiency—half the fuel savings during highway cruising come from optimized cycle design.

[Lucille]

The working cycle of a gasoline engine refers to the key steps in engine operation. First, the intake stroke draws in the air-fuel mixture; second, the compression stroke pressurizes the mixture; third, combustion occurs when ignited, generating thrust; fourth, the exhaust stroke expels the waste gases. Only with a proper cycle can the car run smoothly. Having driven for over a decade, I deeply understand how this cycle affects fuel consumption. Regularly replacing the air filter prevents intake blockage, timely spark plug replacement ensures accurate ignition, and poor compression makes the engine sound labored. When choosing a car, prioritize the cycle design over flashy appearances.