What Are the 4 Cycles of an Engine? A Simple Guide
August 11, 2025Do you understand how the engine of your car functions? If you do not, do not worry. In this blog, we will discuss the 4-cycle engine. From the start to the end(intake to exhaust). We will also discuss how it works step by step. In the process, you will know the reasons behind the overall use of the engine.
A four-cycle of an engine is also known as a 4-stroke of an internal combustion engine. In a 4-stroke engine model , operation is completed in 4 cycles: fuel intake, compression, combustion, and exhaust. In one complete cycle, the piston moves 2 times down and 2 times up.
Moreover, four-cycle engines are used in cars, trucks, generators, and automobiles due to their efficient fuel consumption and reduced smoke emissions. However, these engines are a bit heavier and more pricey compared to other types.
You can also buy a internal combustion engine model kit from us, for educational or display purposes.
How does a 4-cycle of an engine work
In this section we will discuss the working of 4-cycle of an engine work:Step 1) Intake stroke
The intake valve is opened when the piston moves from the upper side to the lower side. As a result, fresh air or a mixture of air and fuel is sucked in due to the vacuum ( imagine a syringe pulling out liquid ).
At this stage, Piston rings help in sealing the cylinder so that no mixture escapes during the intake phase.
Step 2) Compression stroke
The next motion of the piston will change to the ‘up’ position. In this case, the intake and exhaust valves are closed. As a result, they compress the air-fuel mixture (or air) in the cylinder, increasing its temperature and pressure.
At this point, Piston rings also prevent leaks during the compression stage, helping the engine hold optimal pressure. Ultimately, the main goal is to facilitate easier and more powerful combustion.
Step 3) Power stroke
Now the mixture of air and fuel within the cylinder is completely under pressure. At this point, a small flame is produced by the spark plug within the cylinder. This flame ignites the mixture, resulting in the generation of huge heat and pressure.
Moreover, because of this high pressure, the gases apply great force onto the piston, pushing it downward. The drop of the piston causes the crankshaft to rotate.
Furthermore, some of the energy is also stored in the flywheel, which helps maintain smooth operation throughout the engine. Consequently, during this power stroke, the engine creates rotational motion used to run the vehicle.
Step 4) Exhaust stroke
After that, the air-fuel mixture has completed combustion. The cylinder contains combustion products, or exhaust gases. Then, the exhaust valve opens.
Simultaneously, the flywheel that had previously stored energy during the power stroke now helps push the piston upwards smoothly using that stored energy. The movement upwards pushes the burnt gases out through the exhaust valve.
Afterward, the intake stroke starts, thus repeating the cycle of the engine continuously.
However, this is just a simple cycle for all ICE engines but if you want to know Internal combustion engine types based on stroke, fuel type, and shape, then click here.
Quick Summary Table
Now we understand how 4 four-cycle of engine works step-by-step. Here we will discuss in a table summarizing the important actions that take place during each stroke:
| Stroke | Piston movement | Valve action | What happened |
| intake | down | The inlet valve opens | Air-fuel mixture enters the cylinder |
| compression | up | All valves closed | The mixture is compressed |
| Power | Down | All valves closed | Spark ignites the mixture = power created |
| exhaust | up | Exhaust valve open | Waste gases are pushed out |
Barry Williams is a Quora writer who has been shooting for over fifty years. He shared his knowledge about two-cycle and four-cycle engines. To start off, he explained the four-cycle engine. He said its operation is divided into four distinct stages.
The first step is the opening of the intake valve and the intake of air and fuel whilst the piston is going down. After the first step, the piston goes up to compress the mixture while the valves are closed for the second step. In the final step, the piston goes down to replace the power ignition of the mixture with a spark plug ignition.
Once the exhaust valve opens, the piston moves up to extract the burned gases. As he explained, this provides one power stroke for every two turns of the crankshaft. Next, he explained two-cycle engines, saying, “They work faster.” First, a piston rides up, compresses, and is ignited by the spark plug.
Then, it is released, and the piston opens ports to let out exhaust. New fuel comes in at the same time. He said that the two-cycle engines have a higher power-to-weight ratio, but. They generate more power, but at a cost of higher fuel consumption and more noxious emissions.
Why 4-Cycle Engines Are Popular
Today, almost all cars, machines, and bikes utilize 4-cycle engines. But what makes them so popular? Let us examin:
-
They Use Less Fuel: First of all, 4-cycle engines burn fuel more completely. You receive more energy while spending less. As such, your car travels a greater distance on less gas.
-
They Make Less Smoke: Next such engines emit less harmful exhaust fumes; hence they are better for the environment. This is why they comply with emission regulation in most countries.
-
They Last Longer: Due to the way the engine operates in a smooth and balanced manner, the parts are not subject to rapid wear and tear. This is the reason why 4-cycle engines remain in good condition for many years.
-
They Run Smoothly: Moreover, when power comes from one stroke while the other three help the engine stay balanced. In the distance one can hear the rhythm of the engine while driving.
-
They Are Not Too Noisy: Last but not least, when it comes to noise levels, 4-cycle engines are quieter than 2-stroke engines. This makes 4-cycle engines better for regular driving, as well as for use in towns and cities.
Conclusion
Now you understand the function of the 4-cycle engine. It works in a sequence of four steps. Each step has an individual task. That is the way your automobile or motorcycle operates. Additionally, the amount of smoke emissions is reduced, and less fuel is consumed. Therefore, you can rely on it for everyday purposes. Most modern automobiles use it for that reason.
To observe these engine strokes in real action, check out the realistic engine models we offer at EngineDIY, ideal for learning, testing, or even for display. There is no better way to learn engine mechanics.