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A 5.9 liter medium-heavy-duty diesel engine, meeting the emissions performance of a MY 2000 US heavy-duty on-highway engine, was tested with and without a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and adsorber catalysts NOx arranged in a four-flow path configuration. This four-flow path system represents a significant reduction in catalyst volume when compared to previous systems tested by EPA. The goal of this project was to achieve high NOx reduction over the Heavy-Duty Diesel Engine Federal Test Procedure (HDDE-FTP) and Supplemental Emission Test (SET), consistent with the 2007 U.S. heavy-duty engine emissions standards, using this reduced volume system. Supply of hydrocarbon reductant for NOx adsorber regeneration was accomplished via a secondary exhaust fuel injection system.

A 5.9 liter medium-heavy-duty diesel engine, equipped with a diesel exhaust emission control system consisting of catalyzed diesel particulate filters (CDPF) and NOx adsorber catalysts arranged in a dual-path configuration, was evaluated with the goal of developing desulfation strategies for in-use NOx adsorber desulfation. NOx adsorber desulfation was accomplished by providing reductant via a secondary exhaust fuel injection system and exhaust flow via an exhaust bypass valve. An alternating restriction of the exhaust flow between the two flow paths allowed reductant injection and adsorber desulfation to occur under very low space velocity conditions. An exhaust bypass valve connecting the dual path configuration upstream of the catalyzed diesel particulate filters allowed controlled addition of exhaust into the desulfating pathway for desulfation method development.