RESUMO
Real world vehicle emission tests were conducted on two heavy-duty diesel trucks on un-loaded and loaded condition by using a portable emission measurement system. By analysis, the results indicate high fuel consumption and emission rates are concentrated on the high speed and acceleration areas of the speed-acceleration emission maps and the areas are much wider on loaded condition. The impact of load on fuel use and emissions will be highest while the vehicle is cruising or accelerating on (30 +/- 2.5) km x h(-1), which are 1.6 - 3.2 times of those on un-loaded condition. Synthetically, the comprehensive fuel consumption and CO, HC, NO(x) emission factors of truck I and truck II on loaded condition are respectively 1.6, 3.5, 1.1, 1.5 times and 1.2, 1.0, 0.9, 1.5 times of those without load. Load has greatest impact on fuel consumption and NO(x) emission and less effect on HC emission. As for the CO emission, it depends on the maintenance of the truck. It can be figured out from the results on two trucks that the impact of same load will be lower on a vehicle with lager type and more powerful engine, which means if one vehicle is loaded on its acceptable range of GVWR, fuel use and emissions caused by heavy loads could be decreased correspondingly.