What is a four-stroke engine and how does it work?

The four-stroke engine is one of the types of engines currently most used for industrial machinery, vehicles and agricultural machines, since it is less polluting than other engines and offers better performance.

In this article we review what a 4-stroke engine is and how it works.

What is a four-stroke combustion engine?

A four-stroke engine is a type of internal combustion engine that performs its operating cycle in four phases. These types of engines need two complete turns of the crankshaft to carry out a complete combustion cycle.

The four-stroke combustion engine converts the chemical energy of the fuel into heat energy for the operation of the engine, transforming the mixture of gasoline and air in motion.

How does a four-stroke engine work?

Four-stroke engines work in four phases : fuel intake, compression, explosion, and exhaust. In these four stages, the engine is put into operation by different reactions that occur inside it.

The four strokes of an internal combustion engine

1. Admission phase.

It constitutes the first phase of the operating cycle of the 4-stroke engine. This phase begins when the piston is at top dead center. The intake valve opens, and as the piston moves down, a suction effect is created that draws fuel into the cylinder.

2. Compression phase.

In this phase, the intake valve closes and the piston begins to rise, producing compression of the air-fuel mixture. The crankshaft will have made one complete revolution at the end of this phase.

3. Explosion or combustion phase.

When the piston reaches dead center and the valves are closed, the mixture is fully compressed and the spark plug generates the spark that initiates the explosion of the fuel-air mixture.

4. Escape phase.

In the last phase, the exhaust valve opens, the piston moves upwards and the gases generated during the previous phase are expelled.

At the end of the last stage, the crankshaft will have made two full turns and the cycle will start all over again.

Differences between two-stroke and four-stroke engines

TWO-STROKE ENGINE

They work with two phases

1 turn of crankshaft

shorter useful life

less efficient

higher power

They generate more polluting emissions

consume more fuel

FOUR-STROKE ENGINE

They work with four phases

2 turns of crankshaft

longer useful life

more efficient

lower power

They generate less polluting emissions

consume less fuel

Now you know more about four-stroke combustion engines, remember that at Comercial Méndez we are official distributors of the most prestigious engine brands. Take a look at our large stock !