Difference between the first three strokes of Diesel Engine with those of Petrol Engine

Diesel Engine

1. In the first stroke the intake stroke, air is sucked in the cylinder.

2. During the second stroke the compression stroke, air is compressed to about 1/16th of the initial column whereby its temperature rises to about 1000oC.

3. In the third stroke, the power stroke, diesel is injected into the cylinder in the form of a fine spray. The combustion takes place due to the high temperature of the compressed air. The gaseous products produced push the piston outward.

Petrol Engine

1. In the petrol engine, petrol air-mixture is sucked in the cylinder during intake stroke.


2. In the petrol engine, the fuel-air Mixture is compressed to about 1/8th of its original volume during compression stroke.

3. In the petrol engine, during power stroke, the combustion of fuel-air mixture is started by a spark plug. The gaseous products formed push the piston outward.