1. Petrol engine and diesel engine 1. Cycle ( Otto and diesel) 2. comparison

2. Otto cycle ( theoretical) Suction stroke Compression stroke Working stroke Exhaust stroke

3. Suction stroke Stroke is represented by the line horizontal line AB.

4. Compression stroke Reversible adiabatic Represented by curve BC. Constant volume combustion process represented by vertical line CD.

5. Working stroke Process is represented by the line DE. (reversible adiabatic process) Exhaust opens and drop in pressure is represented by EB.

6. Exhaust stroke Process is represented by a horizontal line BA.

7. Diesel cycle

8. Suction stroke This process is represented by the horizontal line AB.

9. Compression stroke Adiabatic process represented by the line BC.

10. Power stroke Constant pressure expansion due to combustion of fuel is represented by CD. Expansion of burnt gases represented by the curve DE.

11. Exhaust stroke Exhaust port opens at end of previous stroke represented by curve EB. Exhaust gases expelled out represented by the curve BA.