What is a Four Stroke Engine?


The four-stroke engine is a common type of internal combustion engine. Most modern cars are four-stroke internal combustion engines that use gasoline or diesel.

While the engine is running, the piston comes out of 4 to reach each electrical cycle. The definition of a stroke is the upward or downward movement of the piston. After completing all 4 events, the cycle is complete and ready to start again.

It has a compressor in which the piston moves up and down for air compression. The 2-stroke engine has low efficiency than the 4-stroke engine but four-stroke engines have high weight than two-stroke engines. The four-stroke engine affects the good balance between power, reliability, and efficiency. In terms of greenhouse gas emissions, four shocks mechanically separate each event, thereby reducing the emission of unburned gases. It can also separate the oil from the fuel and significantly reduce carbon monoxide emissions. The combination of these excellent characteristics made the 4-stroke engine one of today’s passenger cars.

What are the strokes of a four-stroke engine?

To effectively operate the equipment, the four-stroke engine completes and repeats the following steps:

Intake Stroke
  • The piston travels along the cylinder from top dead center (TDC) to bottom dead center (PMI)
  • The inlet valve opens and the outlet valve closes.
  • The downward movement of the piston creates a vacuum (negative air pressure) that draws a mixture of air and fuel into the engine through an open inlet valve.

Compression stroke

  • The piston moves the cylinder from bottom dead center to top dead center
  • Both inlet and outlet valves are closed
  • Moving towards the piston compresses the air-fuel mixture in the combustion chamber.

Power Stroke

  • At the end of the pressure stroke (top), the spark plug ignites, igniting the mixture of compressed air and fuel. This ignition / explosion forces the piston into the cylinder, turns the crankshaft and propels the car forward.
  • The piston moves from top dead center to bottom dead center.
  • Both inlet and outlet valves are closed

Exhaust Stroke

  • The piston moves the cylinder from bottom dead center to top dead center. The motion caused by a power jolt is the force which resumes the movement of the crankshaft and resumes the other 3 blows.
  • The inlet valve is closed and the outlet valve is open.
  • This final blow pushes the exhaust / exhaust gases out of the cylinder. The rotation is complete and the piston is ready to start moving.

Working of the Four Stroke Engine

The working of the four-stroke engine is given below:

Intake stroke: Intake valve opens (in the left corner of each image). When the piston is down, this intake draws the air-fuel mixture into the cylinder.

Compression stroke: Now that both valves are closed, the piston compresses the air to a smaller volume in preparation for combustion.

Power stroke: When both valves are closed, the spark plug, located between the inlet and outlet valves, ignites and ignites the air/fuel mixture. The resulting explosion pushed the piston down, turning the crankshaft and moving the car.

Exhaust Stroke: The exhaust valve (in the upper right corner of each image) is pre-open, allowing the piston to drain fuel as it rises. 4 stroke (1 engine cycle) is now complete, repeat the process.

Air is compressible. When air/fuel is compressed before combustion, combustion efficiency increases. The density ratio is the ratio of the total volume of the cylinder to the volume of compression. For example, a 10: 1 compression ratio (orally referred to as “10 to 1”) means that the chamber compresses 10 parts of the air/fuel volume into 1 part at the end of the compression stroke.

In some applications, a higher compression ratio can provide more power. Failure of higher density ratios can reduce life and require the use of high-octane fuels.