| PETROL (SPARK IGNITION) ENGINE | DIESEL (COMPRESSION IGNITION) ENGINE |
| Petrol engine works on Otto cycle. | Diesel engine works on Diesel cycle. |
| In petrol engine, a mixture of petrol and air is admitted into the cylinder during suction stroke with the help of carburetor. | Diesel is injected directly into combustion chamber at high pressure at the end of compression stroke. Carburetor is eliminated but high pressure fuel pump and injector is required. |
| Throttle valve in carburetor controls the quantity of mixture introduced in combustion chamber. | Quantity of fuel is regulated by fuel pump. |
| Petrol engine requires an ignition system with spark plug in combustion chamber. | No spark plug is combustion of fuel is spontaneous due to very high pressure and temperature in combustion chamber. |
| Compression ratio is about 6 to 10.5. | Compression ratio is about 14 to 22. |
| Higher r.p.m. due to lighter weight. | Maximum r.p.m. is lower. |
| Maximum efficiency is lower (about 30 %) due to low compression ratio. | Higher efficiency (about 40 %) due to higher compression ratio. |
| Engine can be easily startėd due to low compression ratio. | Engine cannot be started easily due to high compression ratio. |
| Petrol engine is lighter in weight. | Diesel engine is heavier due to higher pressure. |
| Petrol engines are generally employed in light duty vehicles like scooters, cars etc. | Diesel engines are generally employed in heavy vehicles like bus, truck etc. |
APPLICATION OF IC ENGINE
Four stroke petrol engine :
These engines are generally used in light vehicles such as passenger cars, scooters etc.
Two stroke petrol engine :
These engines are generally used in light vehicles such as scooters, motor cycles as it is light and compact.
Four stroke diesel engine :
These engines are generally used in heavy duty vehicles such as buses, trucks, tractors, pumping sets, diesel locomotives and in I.C. engine power plants etc.
Two stroke diesel engine :
These engines are generally employed in marine propulsion.
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