A Comprehensive Comparison of Petrol and Diesel Engine







  • Suction Strokes

A mixture of air and fuel is drawn inside the combustion chamber of petrol engine while in the case of diesel engine only air is drawn in during suction stroke



  • Fuel Supply

In petrol engine carburetor is used to prepare the mixture of air and fuel and inject it into engine while fuel in used in diesel engine which inject only a fine spray of fuel in engine at the end of compression stroke



  • Pressure

At the end of compression stroke there is pressure on 10 bar in petrol engine and 35 bar in diesel engine



  • Fuel Ignition System

 Petrol engine have a spark plug to ignite the air fuel mixture while in diesel engine highly compressed air have temperature about 600 degree C which is enough to ignite the fuel.



  • Working Cycle

Combustion of fuel in petrol engine happens at constant volume that is it work on otto cycle while in diesel engine combustion happens at constant pressure that means it work on diesel cycle



  • Compression ratio

Petrol engine small compression ratio of about 6 to 10 but diesel engine have high compression ratio of about 15 to 25



  • Starting

Petrol engines are easy to start than diesel engine because less compression ratio



  • Weight

For higher compression heavy head is needed that’s why diesel engine are heavier than petrol engines



  • Cost

Due to light weight and cheap fuel petro engines are cost effective than diesel engine and maintenance cost of petrol engine is also less than the diesel engine



  • Thermal efficiency

Thermal efficiency of petrol engine is about 26 % whereas diesel engine have thermal efficiency of about 40 %



  • Speed

Petrol engines are high speed engines and diesel  engines are low speed engines



  • Applications

Light duty vehicles like motor bike, car etc have petrol engines whereas heavy duty vehicles have diesel engine




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