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. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity. The primary technology being addressed by these projects is the sulfur tolerance of the NAC/DPF system and the durability implications of varying fuel sulfur levels. The test bed for one project in this activity is a 2500 series Chevrolet Silverado equipped with a 6.6L Duramax diesel engine certified to 2002 model year (MY) Federal heavy-duty and 2002 MY California medium-duty emission standards.
While NAC systems have demonstrated extremely high levels of NOX reduction in steady-state laboratory evaluations, the application of a NAC system to an actual transient engine application requires the development of an integrated engine/emissions management system [1,2,3,4,5,6,7,8,9,10]. This paper discusses the integrated engine/emissions system management and regeneration control strategies that were developed. The final control strategies achieved over 98% reductions in tailpipe NOX mass emissions over the hot-start portion of the light-duty Federal Test Procedure (FTP-75). The discussion will cover NOX mass storage modeling and NAC regeneration management strategies for transient operation over the FTP-75, Highway Fuel Economy Test (HFET), and US06 test (an aggressive driving procedure from the supplemental FTP test) cycles.