A FWD vehicle has the following data: Front axle weight: 1750 lbs Center of gravity height: 17 inch Air drag coefficient: 0.32 Tire radius: 11.70 in. Powertrain efficiency: 0.94 Max. Power @6000RPM: 138 HP Torque(ft.b) 140 The manual transmission used for the vehicle has six forward speeds and the gear ratios are: first gear (3.72), 2nd gear (2.31), 3d gear( 1.51), 4th gear (1.07), 5 gear (0.81), 6 gear (0.63). The engine WOT output plot is given below: 130 120 110 100 90 Torque 1000 Homework 1 2000 3000 4000 Rear axle weight: 1550 lbs Wheel base: 104 in. Frontal projected area: 22.90 square feet Roll resistance coefficient: 0.018 Speed (RPM) Traction coefficient: 1.0 Max. Torque @4500RPM: 132 Power 5000 6000 150 125 100 75 25 7000 Power (HP) a) The engine RPM drops 662 (RPM) when a 4-5 upshift is made at a vehicle speed of 45 mph. Determine the final drive ratio of the vehicle. b) Determine the engine torque and the engine power when the vehicle is cruising at a constant speed of 65 mph on level ground in the 6th and 5th gear respectively. e) Determine the maximum acceleration the vehicle can achieve in the 4th gear at a speed of 65 mph on a 2% slope. d) What is the highest speed the vehicle can achieve in the 6 gear on level ground? e) Redesign the 6th gear ratio for the highest vehicle speed possible based on maximum engine power. f) Redesign the gear ratio for the lowest gear for the maximum gradability using a reservation factor B=1.35.

Fig: 1