Examination of a Heavy Heavy-Duty Diesel Truck Chassis Dynamometer Schedule

Repeatable measurement of real-world heavy-duty diesel truck emissions requires the use of a chassis dynamometer with a test schedule that reasonably represents actual truck use. A new Heavy Heavy-Duty Diesel Truck (HHDDT) schedule has been created that consists of four modes, termed Idle, Creep, Transient and Cruise. The effect of driving style on emissions from the Transient Mode was studied by driving a 400 hp Mack tractor at 56,000 lbs. test weight in fashions termed “Medium”, “Good”, “Bad”, “Casual” and “Aggressive”. Although there were noticeable differences in the actual speed vs. time trace for these five styles, emissions of the important species oxides of nitrogen (NO_x) and particulate matter (PM), varied little with a coefficient of variation (COV) of 5.13% on NOX and 10.68% on PM. Typical NO_x values for the HHDDT Transient mode ranged from 19.9 g/mile to 22.75 g/mile. The Transient mode which was the most difficult mode to drive, proved to be repeatable. Measurements using the Idle mode showed that engine auxiliary loads can affect run-to-run repeatability. Air conditioning and alternator loads, which the driver can control, affect emissions. There is also variability of distance specific emissions from run-to-run in the Creep mode, due to auxiliary loads and due to the small distance that is traveled during the mode.