What is Basic Difference Between SI and CI Engines?

SI Engine means Spurk ignition and CI engine means compression ignition.

1. SI Engine based on Otto Cycle and CI engine based on Diesel cycle.

2. SI engine petrol used as a fuel but CI engine used diesel oil as a fuel.

4. In SI engines requires an ignition system with spark plug in the combustion chamber. But CI engine is self ignition due to high temperature caused by high compression of air when fuel is injected.

1. In SI engine Fuel and air introduced as a gaseous mixture in the suction stroke. But CI engine Fuel in ijected directly into combustion chamber at high pressure at the end of compression stroke.

5. In SI engine compression ratio is 6 to 10.5 but CI engine compression ratio is 14 to 22.

6. In SI engine higher maximum revolution per minute due to lighter weight. But cases of CI engine maximum revolution per minute is lower.

7. In SI engine maximum efficiency lower due to low compression ratio but higher maximum efficiency due to higher compression ratio.

8. In SI engine weight is lighter but CI engine heavier due to higher pressures.

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