SI Engine : Working, Application, Advantages and Disadvantages

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What will you learn after reading this article?

  • Concept of Working of SI engine with its application.
  • Advantages and Disadvantages of these engines.

SI engine stands for spark ignition engine. Spark ignition engine means any engine in which fuel is ignited by a spark plug or by a predefined ignition source. Many of us have misconception that only petrol engines are SI engines but actually petrol engine is a type of SI engine. There are many other Spark ignition engines like gas engines, Hydrogen engines, LPG engines etc.

SI Engine:

SI Engine : Working, Application, Advantages and Disadvantages

Working of SI Engine:

In this type of engine, a correct amount of fuel air mixture drawn into cylinder where it compressed and a spark plug ignite this compressed mixture. This will starts combustion process which generates a high pressure force which is used to drive piston and crankshaft. This is general working of Spark Ignition engine. 
According to the design, this engine can classified into two types.

1. Four Stroke Engine
2. Two Stroke Engine



  • Two stroke SI Engines are used in small vehicles like mopeds and scooters.
  • These engines are used for lawn movers.
  • These are used in small electricity generating sets and pumping sets.
  • Four stroke SI engines are largely used in automobile industries.
  • CNG engines are used in buses.
  • Radial SI engines are used in small aircraft.

Advantages and Disadvantages:


  • These engines have lower cost.
  • They generate high rpm at low torque.
  • It creates less pollution compare to CI engines.
  • These engines are light in weight and required less space. 


  • SI engines have low efficiency compare to CI engine.
  • These engines are not economical at high load.
  • Higher fuel consumption.
  • Knocking problem.

Now you should ask yourself these questions?

  • What is SI Engines?
  • Why SI engines are light weighted?
  • How SI engines woks?

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