A Comparison of Carbon Dioxide Exhaust Emissions and Fuel Consumption for Vehicles Tested over the NEDC, FTP-75 and WLTC Chassis Dynamometer Test Cycles

Due to concern over emissions of greenhouse gases (GHG; particularly carbon dioxide - CO₂), energy consumption and sustainability, many jurisdictions now regulate fuel consumption, fuel economy or exhaust emissions of CO₂. Testing is carried out under laboratory conditions according to local or regional procedures. However, a harmonized global test procedure with its own test cycle has been created: the World Harmonized Light Vehicles Test Cycle - WLTC. In this paper, the WLTC is compared to the New European Driving Cycle (NEDC) and the FTP-75 cycle used in the USA. A series of emissions tests were conducted at BOSMAL on a chassis dynamometer in a Euro 6-complaint test facility to determine the impact of the test cycle on CO₂ emissions and fuel consumption. While there are multiple differences in the test cycles in terms of dynamicity, duration, distance covered, mean/maximum speed, etc, differences in results obtained over the three test cycles were reasonably limited. However, in most cases the NEDC produced the highest results, despite its relatively undemanding speed trace. This result concurs with other published studies. Where the same road load simulation settings are used, inter-cycle differences rarely exceed 5%. The results were subjected to various analyses and considerations; it appears that the additional distance covered by the FTP-75 and WLTC ensure that results are lower than might be expected based on the transient nature of the cycle. The usage of the gearbox, the speed trace during initial portions of the cycle and engine warmup behavior were also briefly considered.