Design of an On-Road PHEV Fuel Economy Testing Methodology with Built-In Utility Factor Distance Weighting

As vehicle technology progresses to new levels of sophistication, so too, vehicle test methods must evolve. This is true for analytical testing in a laboratory and for on-road vehicle testing. Every year since 1993, the U.S. Department of Energy (DOE) and original equipment manufacturer (OEM) sponsors have organized a series of competitions featuring advanced hybrid electric vehicle (HEV) technology to develop and promote DOE goals in fuel savings and alternative fuel usage. The competition has evolved over many years and has included many alternative fuels feeding the prime mover (including hydrogen fuel cells). EcoCAR turned its focus to plug-in hybrid electric vehicles (PHEVs) and it was quickly realized that to keep using on-road testing methods to evaluate fuel and electricity consumption, a new method needed to be developed that would properly weight depleting operation with the sustaining operation, using the established Utility Factor (UF) method. A new approach using three separate trips was devised for the on-road emissions and energy consumption event that matches the Fleet UF found in SAE J2841. This paper explains the method and shows the remarkable fit from the three-trip approach compared to the actual UF curve which was constructed using a data set of over 30,000 vehicle-days of travel.