Assessment of Heavy-Duty Diesel Vehicle NOx and CO₂ Emissions Based on OBD Data

Controlling NOx and CO₂ emissions from heavy-duty diesel vehicles (HDDVs) is receiving increasing attention. Accurate measurement of HDDV NOx and CO₂ emissions is the prerequisite for HDDV emission control. Vehicle emission regulations srecommend the measurement of NOx and CO₂ emissions from vehicles using an emission analyzer, which is expensive and unsuitable to measure a large number of vehicles in a short time. The on-board diagnostics (OBD) data stream of HDDVs provides great convenience for calculating vehicle NOx and CO₂ emissions by providing the engine fuel flow rate, NOx sensor output, and air mass flow. The calculated vehicle NOx and CO₂ emissions based on the OBD data were validated by testing a heavy-duty truck’s emissions on the chassis dynamometer over the CHTC-HT driving cycle, showing that the calculated NOx and CO₂ emissions based on the OBD data are consistent with the measured results by the emission analyzer. The calculated vehicle fuel consumptions based on the OBD data were close to the calculated results based on the carbon balance method and the measured results by the fuel flowmeter. The experimental results show that accessing vehicle NOx and CO₂ emissions based on the OBD data is a convenient and applicable method.