Petrol engine Vs Diesel engine ?

Petrol engine draws a mixture of petrol and air during suction stroke.
Carburetor is employed to mix petrol and air in the required quantity and supply it to the engine during suction stroke.
Pressure at end if compression about 10 bar.
Charge is ignited with help of spark plug.
Petrol engine works on Otto cycle, combustion of fuel take a place at constant volume.
Compression ratio of petrol engine is 6 to 10.
Starting of engine is easy due to low compression ratio.
Very lighter and cheaper then diesel engine.
Petrol engine running cost is high because higher cost of petrol.
Low maintenance cost.
Thermal efficiency is up to 26 %.
Over heating trouble is more due to low thermal efficiency.
These are high speed engines.
The petrol engines are generally employed in light duty vehicle such as scooters,motor cycles cars,these are also used in aeroplanes.

A Diesel engine draws only air during suction stroke.
The injector is employed to inject the diesel at the end of compression stroke.
The pressure at the end of compression is about 3.5 bar.
The fuel is formed in form of fine spray.the temperature of the compressed air ( about 600 deg at a pressure of about 35 bar ) is sufficiently high to ignite the fuel.
The combustion of fuel takes place approximately at constant pressure ,In other words ,it works on diesel cycle.
The starting is little difficult due to high compression ratio.
As the compression ratio is high,the diesel engines are heavier and costlier.
Diesel engine running cost is low because lower cost of petrol.
More maintenance cost.
Thermal efficiency is up to 40 %.
Over heating trouble is less due to high thermal efficiency.
These are low speed engines.
The diesel engines are generally employed in heavy duty vehicle such as buses, trucks, and earth moving machines, etc.

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