Vehicle road load power (hp) 40 Problem 1. Solve problem 1.69 of the textbook. How steep a grade can be climbed by the automobile in Sample Problem 1.3 (with a 2.64 axle ratio) while maintaining a constant 55 mph: a) With transmission in direct drive? b) With a transmission reduction ratio of 1.6? 55 mph 2.64 axle ratio SAMPLE PROBLEM 1.3 Automotive Performance Analysis Figure 1.7 shows a representative engine power requirement curve for constant speed, level road operation of a 4000-lb automobile. Figure 1.8 shows the wide-open-throttle horsepower curve of its -- 350 in V-8 engine. Figure 1.9 gives specific fuel consumption curves for the engine for the vehicle shown in Figure 1.10. The extreme right-hand point of each curve represents wide-open-throttle operation. The rolling radius of the wheels varies a little with speed, but can be taken as 13 in. The transmission provides direct drive in high gear. 160 160 120 20 40 60 80 100 120 Vehicle speed (mph) FIGURE 1.7 Vehicle power requirement. Typical 4000-lb sedan (level road, constant speed, no wind). Engine output power (hp) 120 0 0 1000 2000 3000 4000 5000 Engine speed (rpm) FIGURE 1.8 Engine output power versus engine speed. Typical 350-in.3 V-8 engine.