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9 Differences between SI and CI Engine with Advantages and Limitations of SI engines over CI engines

9 Differences between SI and CI Engine with Advantages and Limitations of SI engines over CI engines:SI Engine stands for Spark Ignition Engine and CI Engine stands for Compression Ignition Engine.Spark Ignition Engine runs by Petrol whereas Compression Ignition Engine runs by Diesel.This is just one difference between SI and CI Engine but in this article,I will be listing out 9 Differences between SI and CI Engine with Advantages and Limitations of SI engines over CI engines in a detailed way.

9 Differences between SI and CI Engine with Advantages and Limitations of SI engines over CI engines
9 Differences between SI and CI Engine with Advantages and Limitations of SI engines over CI engines

9 Differences between SI and CI Engine:

The Differences between SI and CI Engine are listed below in the form of a table.

S.NODESCRIPTION SI ENGINE                     CI ENGINE
1Basic cycle           Otto cycle (const.Volume heat addition)Diesel cycle (const. Pressure Heat addition)
 

2

 

Fuel

Gasoline (petrol)


Highly volatile –Self ignition temp. 

Diesel oil


Non-volatile Self ignition temp.

 

 

3

 

 

Introduction of fuel

1.Gaseous mixture of fuel + air introduced during suction stroke


 

2.Carburetor and Ignition system are required.

1.Fuel directly injected as droplets into Combustion Chamber at high pressure at the end of compression Stroke


2.Fuel pump and Injector are necessary.

4Load ControlThrottle controls the air-fuel mixture introduced.Quantity of fuel is regulated. Air quantity is not regulated.
 

5

 

Ignition

Requires an ignition system with spark plug in the combustion chamber. Primary voltage provided by battery or a magnetoSelf ignition occurs due to high temperature of air because of compression. Ignition system and spark plug are not required.
 

6

 

Compression ratio

6 to 10.

Upper limit is fixed by anti-knock quality of the fuel.

16 to 20.

Upper limit is set by the weight increase of the engine.

 

7

 

Speed  

Due to light weight and homogeneous combustion, they are high speed enginesDue to heavy weight and due to heterogeneous combustion, they are low speed engines.
 

8

 

Thermal efficiency

Because of the lower compression ratio, the max. value of thermal efficiency that can be obtained is lower.Because of higher compression ratio, the max value of thermal efficiency that can be obtained is higher.
9Weight   Lighter construction due to lower peak pressures.Heavier due to higher peak pressures

These are the 9 Differences between SI and CI Engine in a detailed way.Now,the Advantages and Limitations of SI engines over CI engines will be discussed.

Advantages of SI engines over CI engines:

  • For a given output,it is lighter in weight and occupies less space.
  • Initial cost is less
  • Due to low compression,it is easy to start.

Limitations of SI engines over CI engines:

  • Less dependable
  • Suitable only for light duty vehicles
  • Requires costly fuels and maintenance cost is high
  • Chances of pre-ignition of charge was more.

These are the 9 Differences between SI and CI Engine with Advantages and Limitations of SI engines over CI engines in a detailed way.If you have any doubts,feel free to ask from the comments section.

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