COMPARISON OF SPARK IGNITION (S.I) AND COMBUSTION IGNITION

As its name indicates the spark Ignition (SI) engine, uses spark to ignite the fuel. And in Compression Ignition (CI) engine, the air is compressed within the cylinder and the heat of this compression air is used to ignite the fuel. Since spark and compressed air is used to ignite the fuel in these engines, so they are called as spark ignition (SI) engine and compression ignition (CI) engine.
Let's See the major difference between SI engine and CI engine :-

S.no	Aspects	S.I Engines	C.I Engines
1	Thermodynamics	Otto Cyle	Diesel Cycle... For slow speed engines
2	Fuel Used	Petrol	Diesel.
3	Air Flow Ratio	10:1 to 20:1	18:1 to 100:1.
4	Comparison Ratio	Up to 11; Average value 7 to 9;  Upper limit of compression ratio fixed by anti-knock quality of fuel.	12 to 24 ; Average value 15 to 18 ; Upper limit of compression ratio is limited by thermal and mechanical stresses.
5	Combustion	Spark Ignition	Compression Ignition.
6	Fuel Supply	By Carburetor...Cheap method	By injection.....explosive method.
7	Operating Pressure (i)Comparison Pressure  (ii)Maximum Pressure	(i)7 bar to 15 bar  (ii)45 bar to 60 bar	(i)30 bar to 50 bar (ii) 60 bar to 120 bar
8	Operating Speed	High Speed; 2000 to 6000 rpm	Low Speed: 400 rpm.Medium Speed:400 to 1200 rpm.High speed: 1200 to 3500 rpm.
9	Control Power	Quantity Governing... by throttle	Quality Governing... by rack.
10	Calorific Value	44 MJ/KG	42 MJ/KG
11	Cost Of Running	High	Low.
12	Maintenance Cost	Minor Maintenance is required	Major Overhaul required but less frequently.
13	Supercharging	Limited by detonation. Used only in Air Craft Engines.	Limited by blower power and mechanical and  thermal stresses.widely used.
14	Two Stroke Operation	Less Suitable, fuel loss in scavenging.But small two stroke engines are used in mopeds, scooters and motorcycle due to their simplicity and low cost.	No fuels loss in scavenging. More suitable.
15	High Powers	No	Yes
16	Uses	Mopeds,Scooters,Motorcycle,Simple Engine passenger cars,Air Crafts etc..	Buses,Trucks,Locomotives,Tractors,Earth Moving machinery and Stationary Generation Plants