9 Differences between SI and CI Engine with Advantages and Limitations: 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.

Note: Download Differences between SI and CI Engine PDF at the end of the article. 

Read: 11 Classification of IC Engines-Every Mechanical Engineer must know

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.NO DESCRIPTION SI ENGINE                      CI ENGINE
1 Basic 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.A gaseous mixture of fuel + air introduced during the 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.

4 Load Control Throttle controls the air-fuel mixture introduced. A quantity of fuel is regulated. Air quantity is not regulated.
5 Ignition Requires an ignition system with a spark plug in the combustion chamber. The primary voltage provided by a battery or a magneto Self-ignition occurs due to a high temperature of air because of compression. Ignition system and spark plug are not required.
6 Compression ratio 6 to 10.

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

16 to 20.

An upper limit is set by the weight increase of the engine.

7 Speed   Due to lightweight and homogeneous combustion, they are high-speed engines Due to heavyweight 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 the higher compression ratio, the max value of thermal efficiency that can be obtained is higher.
9 Weight   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.

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Advantages of SI engines over CI engines:

  • For a given output, it is lighter in weight and occupies less space.
  • The 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 were 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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Note: PDF Download

You can download Differences between SI and CI Engine PDF by the below links

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Lessons for You:

Thermal Engineering

Theory of Machines

Non-Traditional Machining

CAD/CAM

Material Science Engineering

Production-Casting

Welding

Forming Processes

Machining

Sheet Metal Operations

Elements of Mechanical Engineering

Workshop Manufacturing Practices 

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Mohammed SHAFI

Mr. Mohammed Shafi is an Assistant Professor at Sreenidhi Institute of Science & Technology. By education, he is a Mechanical Engineer and expertise in CAD & CAM. Mechanical Students is his first...

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