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Increasing fuel costs and the desire for reduced dependence on foreign oil have brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. One of the obstacles to the increased use of diesel engines in this platform is the Tier 2 emission standards. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies-such as common rail fuel injection systems, low-sulfur diesel fuel, oxides of nitrogen (NOX) adsorber catalysts or NACs, and diesel particle filters (DPFs)-allows for the development of powertrain systems that have the potential to comply with these future requirements. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity [1, 2, 3, 4, 5].

Increasing fuel costs and the desire for reduced dependence on foreign oil has brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. The main obstacle to the increased use of diesel engines in this platform is the upcoming extremely stringent, Tier 2 emission standard. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies such as common rail fuel injection systems, low sulfur diesel fuel, NOX adsorber catalysts (NAC), and diesel particle filters (DPFs) allow the development of powertrain systems that have the potential to comply with these future requirements. In meeting the Tier 2 emissions standards, the heavy light-duty trucks (HLDTs) and medium-duty passenger vehicles (MDPVs) will face the greatest technological challenges. In support of this, the U.S.

Typically, an engine/dynamometer thermal aging cycle contains combinations of elevated catalyst inlet temperatures, chemical reaction-induced thermal excursions (simulating misfire events), and average air/fuel ratio's (AFR's) to create a condition that accelerates the aging of the test part. In theory, thermal aging is predominantly a function of the time at an exposure temperature. Therefore, if a burner system can be used to simulate the exhaust AFR and catalyst inlet and bed temperature profile generated by an engine running an accelerated aging cycle, then a catalyst should thermally age the same when exposed to either exhaust stream. This paper describes the results of a study that examined the aging difference between six like catalysts aged using the Rapid Aging Test (RAT) cycle (an accelerated thermal aging cycle). Three catalysts were aged using a gasoline-fueled engine aging stand; the other three were aged using a computer controlled burner system.