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Transient exhaust emissions data were collected with a 4.9-L, V6 prototype diesel engine operated on an engine dynamometer using repetitive Highway Fuel Economy Tests (Hwy-FET). This procedure provided sufficient exhaust temperatures during transient operation to characterize the performance of an exhaust treatment system consisting of a diesel oxidation catalyst (DOC) followed by a hydrocarbon selective catalytic reduction (HC-SCR) system for NOx control under conditions typical of “real world”. The goal was to provide data needed for modeling the problem of hydrocarbon deactivation. Repetitive Hwy-FETs highlighted the effects of hydrocarbon deactivation over time. Stochastic Process Modeling showed that the observed catalyst deactivation was due mainly to a change in the reactivity of the catalyst and not to a change in the catalyst inlet conditions.

In the twenty-first century, exhaust emission control will remain a major technical challenge especially as additional pressures for fuel and energy conservation mount. To address these needs, a wide variety of engine and powertrain options must be considered. For many reasons, the piston engine will remain the predominant engine choice in the twenty-first century, especially for conventional and/or parallel hybrid drive trains. Emissions constraints favor the conventional port fuel-injected gasoline engine with 3-way exhaust catalyst, while energy conservation favors direct-injection gasoline and diesel engines. As a result of recent technological progress from a competitive European market, diesels, and most recently, direct-injection (DI) diesels now offer driveability and performance characteristics competitive with those of gasoline engines. In addition, DI diesels offer the highest fuel efficiency.