Differences Between SI Engine and CI Engine

Spark Ignition (SI) engine can be compared with Compression Ignition (CI) engine system in 7 aspects. Those 7 aspects are engine speed, cycle efficiency, fuel used, time of knocking, cycle operation, the pressure generated and constant parameters during the cycle.

Spark Ignition Engine
Compression-Ignition Engine
1 Engine speed SI engines are high-speed engines. CI engines are low-speed engines.
2 Cycle efficiency SI engines have a low thermal efficiency CI engines have high thermal efficiency.
3 Fuel used Petrol is used as fuel, which has a high self-ignition temperature. Diesel is used as fuel, it has a low self-ignition temperature.
4 Time of knocking Knocking takes place at the end of combustion. Knocking takes place at the beginning of combustion.
5 Cycle operation SI engine works on the otto cycle. CI engine works on diesel cycle.
6 Pressure generated A homogeneous mixture of fuel, hence high pressure is generated. A heterogeneous mixture of fuel, hence low pressure is generated.
7 Constant parameter during cycle Constant volume cycle. Constant pressure cycle.
Spread the Knowledge

'ME Mechanical' is an online portal for mechanical engineers and engineering students. Published hundreds of articles on various engineering topics. Visit our about section to know more.

All Comments

  • very good

    hossain Apr 10, 2016 12:39 am Reply
  • thanks it was awesome

    sayed pazhwak Apr 11, 2016 10:35 am Reply
  • Nice one

    Ekundayp Sheriff Jul 25, 2016 12:17 am Reply
  • I find this Information Useful i really appreciate it

    Chindo Benjamin Jul 28, 2016 1:34 pm Reply
  • goods answer

    grijesh chauhan Aug 29, 2016 5:14 pm Reply
  • really thnx a lot thnx u very much

    kanishk Nov 29, 2016 12:28 am Reply
  • thanks a lot…you have written in easy form…..

    Nazmul Hasan Feb 2, 2018 2:58 pm Reply

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.