In - Use Emissions Testing of Light - Duty Diesel Vehicles in the United States

Executive Summary ii EXECUTIVE SUMMARY The Center for Alternative Fuels, Engines and Emissions (CAFEE) at West Virginia University (WVU) was contracted by the International Council on Clean Transportation (ICCT) to conduct in-use testing of three light-duty diesel vehicles, using a portable emissions measurement system (PEMS), over a variety of pre-defined test routes exhibiting diverse driving conditions pertinent to major United States population centers located in the state of California. Additionally, one vehicle was operated over an extended distance of nearly 4000km predominantly composed of highway driving conditions between California and Washington State. Also, two out of the three test vehicles were selected for chassis dynamometer testing at California Air Resources Board's (CARB) El Monte, CA vehicle certification test facility; however, a detailed discussion of these results is not part of this report. The test vehicles were certified to US-EPA Tier2-Bin5 and California LEV-II ULEV emissions limits and were equipped with NO x after-treatment technologies, including one lean-NO x trap (LNT) (Vehicle A) and two urea-based selective catalytic reduction (SCR) systems (Vehicles B and C). Furthermore, all three test vehicles were thoroughly checked for possible engine or after-treatment malfunction codes using an ECU scanning tool prior to selecting a vehicle for this on-road measurement campaign, with none of them showing any fault code or other anomalies. The after-treatment system was assumed to be 'de-greened' as all three vehicles have accumulated more than 3,000 to 4,000 miles, and no reduction in catalytic activity due to aging was expected as the total mileage was relatively low (< 15,000 miles) for all test vehicles. Gaseous emissions of NO x , CO, THC and CO 2 were measured using the OBS-2200 PEMS from Horiba Ltd., while particulate number and mass concentrations were inferred from real-time particle charge measurements employing a Pegasor particle sensor, model PPS-M, from Pegasor. Real-world NO x emissions were found to exceed the US-EPA Tier2-Bin5 (at full useful life) standard by a factor of 15 to 35 for the LNT-equipped vehicle, by a factor of 5 to 20 for one and at or below the standard for the second urea-SCR fitted vehicle over five pre-defined routes categorized based on their predominant driving conditions, namely, i) highway, ii) urban/suburban, and iii) rural-up/downhill driving. The second urea-SCR equipped vehicle exceeded the standard only during rural-up/downhill operating conditions by a factor of ~10. Most importantly, distance-specific NO x emissions for the two high-emitting vehicles were …