What Is the Difference Between a 4-Cycle and a 2-Cycle Engine?

The internal combustion engine depends on introducing fuel and oxygen into the cylinder to burn. The spark plug located at the cylinder does the role of initiating the explosion. The cylinder has a piston that moves up and down, and such motion is called cycles or strokes. In this guide, we will be looking at the difference between a 4-cycle and a 2-cycle engine system.

In a 4-cycle engine, the piston moves 4 times in the cylinder to initiate air and fuel intake, combustion, and emission of exhaust gases. On the other hand, in the 2-cycle engine, the piston moves only two times in the cylinder for air and fuel intake, combustion, and release of exhaust substances.

Difference Between a 4-Cycle and a 2-Cycle Engine

The difference between the 2 and 4-cycle engines is how fast the combustion cycle occurs. The complete combustion of the mixture of fuel and air solely depends on the number of upward and downward movements the piston makes in the cylinder. 

The 4-Cycle Engine

The 4-stroke engine goes through 2 complete revolutions for complete combustion. One revolution is compression, and the last one is the exhaust stroke. At the end of every stroke/cycle, the piston goes to the upper part of the cylinder. The spark plug only fires once after the air and fuel mix in the cylinder, and the end of every 4-stroke is marked by the production of mechanical energy, which initiates motion on all the engine’s moving parts. Such kinds of engines do not need fuel that has been mixed with oxygen, and they have a different oil component. 

The 2-Cycle engine

Only a single piston movement completes the entire combustion in the cylinder. A compression stroke leads to an explosion, and the exhaust gases get out on the return stroke. The spark plug only fires once in every single revolution. Such engines operate efficiently when the fuel and oil are mixed before combustion.

Differences Between the Two Engines

Here are some of the differences between the two engines. After reading, you will be able to make a verdict on which is better and why. 

The 4-cycle engine consumes fuel only once after every 4-cycle, making them more fuel efficient than the 2-stroke engines. 

4-cycle engines are relatively heavy compared to their 2-cycle counterparts, which weigh 50% less than the latter.  

In terms of torque, the 2-cycle engines require a higher RPM to generate torque. On the other hand, the 4-cycle engine generates more torque at a lower RPM.

The 4-cycle engine works quietly, making it the best option for luxury and comfort. On the other hand, the 2-cycle engine is loud when running and usually produces a buzzing sound.

The 4-cycle engines are more durable, while the 2-cycle engines wear out very fast but produce a lot of power. 

The 2-cycle engines require the fuel and oil to mix first, while the 4-stroke engines do not. 


Both the 2 and 4-cycle engines have different working principles to generate mechanical energy. You have learned from this article that they also have various strengths and weaknesses.

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