Due to its high efficiency and superior durability, the diesel engine is again becoming a prime candidate for future light-duty vehicle applications within the United States. While in Europe the overall diesel share exceeds 40%, the current diesel share in the United States is 1%. Despite the current situation and the very stringent Tier 2 emission standards, efforts are being made to introduce the diesel engine back into the U.S. market. In order to succeed, these vehicles have to comply with emissions standards over a 120,000 miles distance while maintaining their excellent fuel economy. The availability of technologies-such as high-pressure, common-rail fuel systems; low-sulfur diesel fuel; oxides of nitrogen (NOx) adsorber catalysts or NACs; and diesel particle filters (DPFs)-allow the development of powertrain systems that have the potential to comply with the light-duty Tier 2 emission requirements. In support of this, the U.S. Department of Energy (DOE) teamed with industry to engage in several testing projects under the Advanced Petroleum Based Fuels - Diesel Emission Controls (APBF-DEC) activity [1; 2; 5; 6; 7; 8]. Three of the APBF-DEC projects evaluated the sulfur tolerance and durability of NAC/DPF systems on various platforms, and one evaluated the performance and durability of a selective catalytic reduction (SCR) system in heavy-duty engines. A fifth project investigated the effects of oil properties on the performance and durability of a NAC.
This project investigated the performance of the emission control system and system desulfurization effects on regulated and unregulated emissions in a light-duty diesel engine. Emissions measurements were conducted over the Federal Test Procedure (FTP), the US06 [an aggressive chassis dynamometer emissions test procedure, part of the Supplemental Federal Test Procedure (SFTP)], and the Highway Fuel Economy Test (HFET). Testing was conducted after the accumulation of 150 hours of engine operation calculated to be the equivalent of approximately 8,200 miles. For these evaluations, three out of six of the FTP test cycles were within the 50,000-mile Tier 2 bin 5 emission standards [0.05 g/mi NOx and 0.01 g/mi particulate matter (PM)]. Emissions over the SC03 (airconditioning test) portion of the SFTP were within limits of the 4,000-mile SFTP standards. Emissions of NOx+NMHC (non-methane hydrocarbons) exceeded the 4,000-mile SFTP standards over the US06 portion of the SFTP. Testing was also conducted after the accumulation of 1,000 hours of engine operation calculated to be the equivalent of approximately 50,000 miles. The results were reported in [7] 2005-01-1755. Recalibrated drivability maps resulted in more repeatable NOx emissions from cycle to cycle. The NOx level was below the Tier 2 emission limits for 50,000 and 120,000 miles. NMHC emissions were found at a level outside the limit for 120,000 miles.