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

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vehicle was carrying a heavy load on one leg of the trip, and was empty on the return leg. The<br />

in<strong>for</strong>mation is shown in Fig. 44 in which it is possible to see that the operation boundaries are not<br />

between 1,300 and 1800 rpm, but rather between 900-1,100 rpm and 2,000 rpm.<br />

Fig. 44. Observed Operation Points (<strong>Truck</strong> 4, Loaded and Unloaded)<br />

These limits were used to generate a series of test points which served as the basis to create several<br />

synthetic duty cycles. These test points are shown in Fig. 45 and summarized in Table 10. In that<br />

table, the time dimension has been added to create a synthetic duty cycle that assesses the<br />

characteristics of the vehicle at these points. Each entry in the table corresponds to a given speed (in<br />

mph) and it is defined by the gear (header), the engine speed level (first column of the table), and the<br />

length of time during which that vehicle and engine speed should be maintained (last column on the<br />

table). Allocating 140 seconds per measurement point – consisting of 120 seconds <strong>for</strong> the target<br />

speed plus 20 seconds <strong>for</strong> the transition from one target speed to the next– the test can be run in about<br />

100 minutes (6,160 seconds as shown in Table 10).<br />

52

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