Driving resistance analysis of long haulage trucks at Volvo

Abstract: To further improve fuel consumption of future trucks and to be able to measure the gains obtained from new inventions, accurate test methods have to be defined. The three main tests currently used at Volvo are: road testing, chassis dynamometer and computer simulations. In this project the three fuel consumption test methods are evaluated with the Volvo FH and its main rivals to get an indication of the results reliability. If the test gives different fuel consumptions but has similar percentage differences between the trucks a fixed relation between test methods is obtained.The chassis dynamometer’s road load is based on the measured force at the vehicle for every vehicle speed. To find this relation a coast down test for each truck is performed; the test is based on continuous logging of vehicle speed and time while driving the equipage at neutral gear from 85-16 km/h. The tests were done in February and consequently weather influenced the results, with wet tracks, winds and low temperatures.The road tests were carried out in April with less restrictive environment, but also using bedded tires and different trailers. The resulting fuel consumption at the Lv-Bo-Lv (Landvetter-Borås-Landvetter) duty cycle for each truck were without exception lower for the road tests compared to the chassis dynamometer results. The percentage difference between the tests were not constant for the different trucks but rather close to the difference in-between trucks attained from the coast downs at full speed, which reflects the Lv-Bo-Lv duty cycle well, (except for the road inclinations). This proves that the coast downs’ were influenced by non-truck specific matters.Great care must be taken during preparation of vehicles prior to fuel consumption and driving resistance tests. Weather influences the results the most and has to be measurably stable between the different tests. The vehicles have to be accurately prepared with similar tires, correctly adjusted deflectors, same trailer and engines with the similar specifications and wear. At the conducted tests several of previously mentioned issues were omitted, the results were therefore heavily affected, finally suggestions for future testing has been established.