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Class-8 Heavy Truck Duty Cycle Project Final Report - Center for ...

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tractors) as well as the maximum torque. Fig. 41 shows a per<strong>for</strong>mance chart based on 1,800 RPM<br />

with an engine operating at 1,550 RPM/62 mph.<br />

Table 9. Gear Ratio and Maximum Torque <strong>for</strong> Transmission Model FRO-16210C*<br />

Gear #<br />

Max TQ<br />

1 2 3 4 5 6 7 8 9 10 lb-ft [Nm]<br />

Gear Ratio 12.69 9.29 6.75 4.90 3.62 2.59 1.90 1.38 1.00 0.74 1650 [2237]<br />

* This transmission can be rated at 100 additional lb-ft torque above the stated limit in the top two gears only.<br />

Fig. 41. Per<strong>for</strong>mance Chart (Based on 1,800 RPM Engine Operating at 1,550 RPM/62 mph)<br />

In addition to this in<strong>for</strong>mation, data related to the optimal operation of the transmission was obtained<br />

from the manufacturer. Fig. 42 shows the engine torque and vehicle speed as a function of engine<br />

revolutions. The highlighted rectangle that goes from 1,450 to 1,550 RPM shows the “sweet-spot” or<br />

ideal area of operation, with the engine speed highlighted values (i.e., 1,300 and 1,800 rpm) showing<br />

the optimum shifting points. For example, a vehicle traveling at 85 mph (upper right corner of the<br />

graph) would be in 10th gear, with the engine operating at about 2,000 rpm and producing a torque of<br />

1,650 Nm. When the speed is reduced to 59 mph (1,332 rpm) then the driver should down shift to 9th<br />

gear (top horizontal arrow pointing to the right); the engine will then operate at 1,800 rpm with a<br />

torque of about 2,000Nm. In 9th gear the speed can be reduced up to 42.8 mph (1,304 rpm) at which<br />

point (to operate under optimal conditions) it would be required to be downshifted to 8th gear, and so<br />

on. The same procedure, but in reverse, would apply to increasing the speed of the vehicle.<br />

50

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