1. A spark-ignition engine is throttled when operating at part load (the inlet pressure is reduced) while the fuel/air ratio is held essentially constant. Part-load operation of the engine is modeled by the cycle shown in Fig. 5-2d (Lecture #9); the inlet air is at pressure p, the exhaust pressure is atmospheric pa, and the ambient temperature is Ta. Derive an expression for the decrease in net indicated fuel conversion efficiency due to throttling from the ideal constant-volume cycle efficiency and show that Anfin = RT ma m+QHV Assume mass fuel < < mass air.