Comparison of Petrol and Diesel Engines
Petrol vs Diesel engines: A comparison - Basic difference between a petrol engine and a diesel engine based on working, pressures, combustion, compression ratios, speed, efficiency, maintenance, and running costs. The following points are important for the comparison of petrol and diesel engines:
1.
Petrol Engines
A petrol engine draws a mixture of petrol and air during suction stroke.
Diesel Engines
A diesel engine draws only air during suction stroke.
2.
Petrol Engines
The carburetor is employed to mix air and petrol in the required proportion and to supply it to the engine during suction stroke.
Diesel Engines
The injector or atomiser is employed to inject the fuel at the end of compression stroke.
3.
Petrol Engines
The pressure at the end of compression is about 10 bar.
Diesel Engines
The pressure at the end of compression is about 35 bar.
4.
Petrol Engines
The charge (i.e. petrol and air mixture) is ignited with the help of a spark plug
Diesel Engines
The fuel is injected in the form of fine spray. The temperature of the compressed air (about 600° C at a pressure of about 35 bar) is sufficiently high to ignite the fuel.
5.
Petrol Engines
The combustion of fuel takes place approximately at constant volume. In other words, it works on Otto cycle.
Diesel Engines
The combustion of fuel takes place approximately at constant pressure. In other words, it works on Diesel cycle.
6.
Petrol Engines
A petrol engine has compression ratio approximately from 6 to 10.
Diesel Engines
A diesel engine has compression ratio approximately from 15 to 25.
7.
Petrol Engines
The starting is easy due to low compression ration.
Diesel Engines
The starting is little difficult due to high compression ratio.
8.
Petrol Engines
As the compression ratio is low, the petrol engines are lighter and cheaper.
Diesel Engines
As the compression ratio is high, the diesel engines are heavier and costlier.
9.
Petrol Engines
The running cost of petrol engines is high because of higher cost of petrol.
Diesel Engines
The running cost of diesel engines is low because of the lower cost of diesel.
10.
Petrol Engines
The maintenance cost is less.
Diesel Engines
The maintenance cost is more.
11.
Petrol Engines
The thermal efficiency is upto about 26%.
Diesel Engines
The thermal efficiency is upto about 40%.
12.
Petrol Engines
Overheating trouble is more due to low thermal efficiency.
Diesel Engines
Overheating trouble is less due to high thermal efficiency.
13.
Petrol Engines
These are high speed engines.
Diesel Engines
These are relatively low speed engines.
14.
Petrol Engines
The petrol engines are generally employed in light duty vehicles such as scooters, motorcycles, cars. These are also used in aeroplanes.
Diesel Engines
The diesel engines are generally employed in heavy duty vehicles such as buses, trucks and earth moving machines etc.
Petrol vs Diesel engines: A comparison - Basic difference between a petrol engine and a diesel engine based on working, pressures, combustion, compression ratios, speed, efficiency, maintenance, and running costs. The following points are important for the comparison of petrol and diesel engines:
Petrol Engines:
Diesel Engines:
1.
Petrol Engines
A petrol engine draws a mixture of petrol and air during suction stroke.
Diesel Engines
A diesel engine draws only air during suction stroke.
2.
Petrol Engines
The carburetor is employed to mix air and petrol in the required proportion and to supply it to the engine during suction stroke.
Diesel Engines
The injector or atomiser is employed to inject the fuel at the end of compression stroke.
3.
Petrol Engines
The pressure at the end of compression is about 10 bar.
Diesel Engines
The pressure at the end of compression is about 35 bar.
4.
Petrol Engines
The charge (i.e. petrol and air mixture) is ignited with the help of a spark plug
Diesel Engines
The fuel is injected in the form of fine spray. The temperature of the compressed air (about 600° C at a pressure of about 35 bar) is sufficiently high to ignite the fuel.
5.
Petrol Engines
The combustion of fuel takes place approximately at constant volume. In other words, it works on Otto cycle.
Diesel Engines
The combustion of fuel takes place approximately at constant pressure. In other words, it works on Diesel cycle.
6.
Petrol Engines
A petrol engine has compression ratio approximately from 6 to 10.
Diesel Engines
A diesel engine has compression ratio approximately from 15 to 25.
7.
Petrol Engines
The starting is easy due to low compression ration.
Diesel Engines
The starting is little difficult due to high compression ratio.
8.
Petrol Engines
As the compression ratio is low, the petrol engines are lighter and cheaper.
Diesel Engines
As the compression ratio is high, the diesel engines are heavier and costlier.
9.
Petrol Engines
The running cost of petrol engines is high because of higher cost of petrol.
Diesel Engines
The running cost of diesel engines is low because of the lower cost of diesel.
10.
Petrol Engines
The maintenance cost is less.
Diesel Engines
The maintenance cost is more.
11.
Petrol Engines
The thermal efficiency is upto about 26%.
Diesel Engines
The thermal efficiency is upto about 40%.
12.
Petrol Engines
Overheating trouble is more due to low thermal efficiency.
Diesel Engines
Overheating trouble is less due to high thermal efficiency.
13.
Petrol Engines
These are high speed engines.
Diesel Engines
These are relatively low speed engines.
14.
Petrol Engines
The petrol engines are generally employed in light duty vehicles such as scooters, motorcycles, cars. These are also used in aeroplanes.
Diesel Engines
The diesel engines are generally employed in heavy duty vehicles such as buses, trucks and earth moving machines etc.
