How does a Petrol Engine work?

The petrol engine (also called gasoline engine) is a positive combustion internal combustion engine designed to use similar gasoline and volatile gasoline.

In a petrol engine, a mixture of air and fuel enters the engine cylinder. The spark plug ignites and ignites the air-fuel mixture. This type of combustion is called constant volume combustion.

Working Principle of Petrol Engine

A petrol engine works on the base of the Otto cycle. The air-fuel mixture containing the correct amount of air explodes in the engine cylinder.


One end is closed the explosion releases heat, increasing the pressure of the combustion gas.

This pressure forces the tightened pistons to move the cylinder down and rotate the crankshaft.

Use the force of the rotating motor shaft for mechanical work. The gas used is discharged from the cylinder before the next combustion to obtain a continuous rotation of the crankshaft.

The new fuel enters the cylinder, and the piston returns to its original position. A set of events is formed that occur in the engine duty cycle. The sequence of events occurring in the petrol engine is as follows:

  1. Suction(inhalation) of air or fuel-to-air mixture into the engine cylinder
  2. Air compression or a mixture of air and fuel within the engine (compression)
  3. Inject fuel into compressed air to burn fuel or burn a fuel-air mixture using an electric spark that generates heat from a spark plug.
  4. Remove all burnt gases from the cylinder to receive a new charge (exhaust gas).

Note: In the case of positive combustion engines, charging refers to introducing fresh air into the cylinder or introducing a mixture of air and fuel into the cylinder.

Types of Petrol Engines

1) Four-stroke engine

In a four-stroke petrol engine, 

the exhaust takes place in the engine cylinder for four events of intake, compression, and force. They are made of four

 Strokes of the piston (i.e., 2 revolutions of the crankshaft). The engine has separate valves to control the charge inlet and the exhaust outlet. The opening and closing of the valve are controlled by a cam mounted on the camshaft. The camshaft is moved from the crankshaft with the help of a suitable gear or chain. The camshaft moves at half the speed of the crankshaft. A 4-stroke petrol engine works in the following way:

1) Suction stroke

In this stroke, the inlet valve opens, and the piston lowers. The outlet valve is closed, and air or a mixture of air and fuel is drawn in.

2) Compression stroke

During this stroke, both valves close, and the piston moves upward. The air-fuel mixture is compressed with an upward impact.

3) Power Stroke

After the fuel burns, it generates a lot of heat and pushes the piston down. Down

The movement of the piston at this time is called a concussion. The connecting rod or pin transmits the force of the piston to the crankshaft, and the crankshaft rotates. During this stroke, both valves close.

4) Exhaust stroke

During this impact, the outlet valve opens, and the piston moves up to remove the burnt gas. The inlet valve remains closed.

Therefore, it was found that there is only one power engine and three idle circuits in four operations in a four-stroke engine. The power stroke provides the strength needed for useful work.

2) Two-stroke engine 

In a two-stroke engine, all events, such as aspiration,

Compression, power, and exhaust are complemented by two-piston strokes (i.e., a crankshaft).

This type of device has no valve. The gas moves through holes called ports in the cylinder. The crankshaft of the motor is hermetic, and the crankshaft rotates on it.

Advantages of Petrol Engines

  • Excellent performance
  • Easy refueling
  • More accessible
  • Style
  • Less release
  • It’s easier to start in cold weather because it’s not stable.
  • Compared to a diesel engine, it has less noise and less vibration.
  • Better burning rate
  • Smooth acceleration
  • High voltage

Disadvantages of the Petrol Engine

  1. Less powerful than diesel engines.
  2. Incorrect fuel mixture can cause engine failure.

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