Road Load Measurement and Dynamometer Simulation Using Coastdown Techniques

Reduction of vehicle road load is important in the overall effort to improve fuel economy in motor vehicles. The ability to accurately simulate vehicle road load on a chassis dynamometer is similarly critical in the process of measuring fuel economy on such a dynamometer. This paper discusses coastdown techniques of road load measurement and dynamometer simulation from the standpoint of SAE Recommended Practice J1263 developed by an SAE Task Force between 1976 and 1979. These techniques are compared to other methods and the equations used to determine the absorber setting which duplicates vehicle road load for a single parameter chassis dynamometer are developed.