What are these SI & CI engines? The difference is actually the mode by which the fuel is ignited. SI here stands for spark ignition engine and CI here stands for Compression Ignition engine. Today we will try to differentiate between the two. CI engin

CI engine

The basic difference between the two is same as that between a petrol engine and a diesel engine. This line is just for you guys to get a small hint of what we are talking about. So here we go.

Operational Cycle: Now SI or spark ignition engines which are also known as petrol engines ignite their fuels on basis of Otto cycle or constant heat volume addition cycle.Here the ignition is carried out with the help of a spark plug. What the spark plug does is, it introduces a spark into the combustion chamber where the fuel and air mixture are present. Whereas in case of a CI engine also known as compression ignition engine (diesel engine) works on the principle of diesel cycle or constant pressure heat addition cycle.Here the ignition of fuel occurs due high pressure and temperature in the combustion chamber. Hence no spark plugs are required in this case.

Also Read: Difference Between Petrol And Diesel

Type Of Fuel: As mentioned earlier SI or spark ignition engines use petrol for working whereas CI or compression ignition engine use diesel as working fuel.

Method of fuel injection: In spark ignition engines the mixture of fuel and air is introduced at the time of suction.For this, it has a carburetor for mixing fuel and air. Whereas in the diesel engine or compression ignition engine the fuel is directly injected into the chamber at a high pressure. Hence CI engine has a fuel pump and fuel injector.

Compression Ratio: