A fully loaded diesel engine operating at sea level runs at 2000 rpm and develops 1000 bhp

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A fully loaded diesel engine operating at sea level runs at 2000 rpm and develops 1000 bhp (750 kW). The initial operating temperature of the engine is 518.7R (288.15K). Metered fuel injection is used, and the specific fuel consumption of the brake is 0.45 lbm/bhp-hr (76 kg/GJ). The engine then operates at an altitude of 5000 ft (1500 m) with a pressure of 12.225 psia (0.8456 bar) and an operating temperature of 500.9R (278.4K). The mechanical efficiency of the engine is 80%, independent of altitude. The brake horsepower at the higher altitude is most nearly Answers 810 hp (630 kW) 860 hp (650 kW) 890 hp (690 kW) 950 hp (740 kW) Why can I not use the "Temperature and Altitude Corrections for Air" chart in chapter 7 - psychometrics when determining the density of air at 5000 ft elevation for use in calculating frictionless horse power equation? I assume the air being drawn into the engine is from outside and doesn't really have sufficient time to heat up to the engine operating temperature. Is this an incorrect assumption to make