Service Manual

ISB, ISBe and QSB (Common Rail [...] Fuel Consumption
Section 5 - Fuel System - Group 05 Page 5-11
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All the test results are based on comparing the fuel used
by the test truck to the fuel used by the control truck.
Drive the truck on a warm-up test run. Drive enough tests
to achieve the following:
• The difference in elapsed time between each test run
can only be ±0.5 percent. This will be ±15 seconds
over 80 km [50 mi] at 97 km/h [60 mph].
The fuel usage of the test truck between test drives must
fall within a 2-percent range (e.g., 2.55 versus 2.60 km/
liters [6.00 versus 6.12 mpg]).
The same range also applies between test drives of the
control truck.
NOTE: The differences in traffic and driving practices can
make the test drive fall out of the 2-percent range.
A minimum of three test drives that meet these conditions
make a valid test. A single test drive is unreliable.
Use the same experienced drivers for all of the tests.
NOTE: The vehicle speeds must be representative of a
typical operation.