Figure 15.3(a) shows the normally aspirated cycle on p-V diagram for the idealized constant volume four-stroke cycle with line 1-5 representing both the induction and exhaust strokes at about the ambient air pressure pa. An ideal p-V diagram for a supercharged constant volume cycle in which the blower or compressor is driven mechanically from the engine is shown in Figure l5.3(b). The physical arrangement is shown in Figure l5.2(a). The inlet pressure to the engine is pi and the exhaust from the engine is at atmospheric pressure pa,. The effects are to increase the pressures reached during the cycle and to give a positive pumping loop l-5-6-7-1 for addition to the main working loop 1-2-3-4-l.