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 ft.lb.

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.