Fig 4.2 and 4.3 show the theoretical Otto cycle and Diesel cycle for naturally aspirated engine and supercharged engine.

In drawing both the cycles, it is assumed that the supercharging ( increase in pressure from pa to p1) is provided by using a separate supercharger. It is obvious from the cycles, that the total power developed in naturally aspirated and supercharged engine per cycle is given by

$An1= (A1-A2) for \ naturally \ aspirated \ air$

$An2= (A1+A2) for \ supercharged \ engine$

But some power is required to increase the pressure of supercharged engine from pa to p1 and that power must be deducted from An2 for getting the net power available from the engine.