A petrol engine, also known as a spark-ignition engine, is a type of internal combustion engine that powers many vehicles today. This chart will illustrate the working principle of a petrol engine.

Components:

• Air Intake System:
  • Includes an air filter to remove dust and debris from incoming air.
  • Air intake manifold: A passage that directs filtered air into the cylinders.
    Air filter in car
• Fuel System:
  • Fuel tank: Stores the petrol (gasoline).
  • Fuel pump: Delivers petrol to the fuel injector.
  • Fuel injector: Injects a precise amount of petrol into the cylinder.
• Cylinder Block:
  • Contains multiple cylinders arranged in a specific layout (inline, V-shaped, etc.).
  • Each cylinder has a piston that moves up and down within it.
• Pistons and Connecting Rods:
  • Pistons compress the air-fuel mixture and transfer the force of combustion to the crankshaft via connecting rods.
• Crankshaft:
  • Converts the reciprocating motion of the pistons into rotary motion.
  • Connects to the wheels through the transmission system.
• Spark Plugs:
  • Located in each cylinder head.
  • Create a spark to ignite the air-fuel mixture at the right moment.
    Spark plug in car engine
• Valves:
  • Intake valves allow air into the cylinder.
  • Exhaust valves allow burnt gases to exit the cylinder.
  • Valve timing is crucial for efficient engine operation.

Four-Stroke Cycle:

The petrol engine operates on a four-stroke cycle, which involves four distinct steps for each cylinder:

1. Intake Stroke:
   • Intake valve opens.
   • Piston moves down, drawing in a mixture of air and fuel from the intake manifold.
   • Exhaust valve remains closed.
2. Compression Stroke:
   • Both intake and exhaust valves are closed.
   • Piston moves up, compressing the air-fuel mixture.
   • This compression increases the temperature and pressure of the mixture.
3. Combustion Stroke (Power Stroke):
   • Spark plug ignites the compressed air-fuel mixture.
   • The burning fuel rapidly expands, pushing the piston down with force.
   • This force is transferred to the crankshaft via the connecting rod.
   • Both intake and exhaust valves remain closed during combustion.
4. Exhaust Stroke:
   • Exhaust valve opens.
   • Piston moves up, pushing out the burnt gases from the cylinder.
   • Intake valve remains closed.
   • The exhaust gases exit through the exhaust manifold and muffler.

Benefits:

This chart, along with the explanation of the four-stroke cycle, provides a clear understanding of how a petrol engine functions. The breakdown of components and their roles simplifies the concept of internal combustion in powering vehicles.