What are the four processes of engine operation?
4 Answers
Engine operation is divided into four cycles: intake, compression, power, and exhaust. Below is the relevant information: 1. Intake: Intake refers to the piston moving downward from the top dead center while the intake valve opens, allowing the cylinder to draw in a mixture of gasoline and air. The intake stroke is completed when the piston reaches the bottom dead center. 2. Compression: Compression refers to the piston moving upward from the bottom dead center while the intake valve closes, compressing the mixed gas drawn into the cylinder. 3. Power: Power refers to the piston moving downward from the top dead center while the spark plug ignites, causing the compressed mixed gas to combust and push the engine to perform work. 4. Exhaust: Exhaust refers to the piston moving upward from the bottom dead center while the exhaust valve opens, expelling the exhaust gases from the cylinder.
As an old car enthusiast who often tinkers with engines, I remember that engine operation is like dancing a four-step. The first step is called the intake stroke, where the intake valve opens, and the piston moves downward, sucking the air-fuel mixture into the cylinder. The second step, the compression stroke, is the most strenuous—both valves are tightly closed, and the piston pushes upward with all its might, compressing the mixture until it's small and hot. The third step is the real explosive moment: the spark plug clicks and ignites, causing the mixture to explode with a bang, forcing the piston to rush downward—this force is the power source that propels the car. Finally, the fourth step is the exhaust stroke: the exhaust valve opens, and the piston sweeps upward like a broom, pushing all the burned exhaust gases out through the tailpipe. These four actions spin so fast that our car can run smoothly.
When teaching my son how cars work, I always use soda as an analogy. The four strokes of engine operation go like this: First, it's like sipping soda through a straw - the piston pulls down to suck in the air-fuel mixture (intake stroke). Then it's like vigorously shaking a soda can - the piston pushes up to compress the mixture to its limit (compression stroke). The most critical moment is the spark plug ignition, just like popping open a soda can - the gas explosion drives the piston downward (power stroke). Finally, it's like pouring out leftover soda - the piston rises to push out exhaust gases (exhaust stroke). These four cycles must rotate smoothly to avoid jerking, which is why older cars often shake when one step goes wrong.
Back when I was teaching newbies at the driving school, I often used a bicycle pump as a demonstration. The four strokes of an engine were clearly explained: Intake is like pulling the pump handle to draw in air, with the piston moving down to suck in the air-fuel mixture. Compression is like forcefully pushing the handle down, with the piston rising to compress the gases. The power stroke is the most special—sparks ignite the gases, causing an explosion that pushes the piston down, which is the force that makes the car lurch forward. Finally, the exhaust stroke is like pulling the handle back to release the waste gases, with the piston pushing out the exhaust. The whole process takes two full rotations of the crankshaft to complete. If any step is missing, the engine won't run.
