Development of a Diesel Passenger Car Meeting Tier 2 Emissions Levels

Increasing fuel costs, the need to reduce dependence on foreign oil as well as the high efficiency and the desire for superior durability have caused the diesel engine to again become a prime target for light-duty vehicle applications in the United States. In support of this the U.S. Department of Energy (DOE) has engaged in a test project under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity to develop a passenger car with the capability to demonstrate compliance with Tier 2 Bin 5 emission targets with a fresh emission control catalyst system. In order to achieve this goal, a prototype engine was installed in a passenger car and optimized to provide the lowest practical level of engine-out emissions. While this optimized calibration proved capable of meeting Euro 4 emission regulations for nitrogen oxides (NO_x) on an engine-out basis, a further reduction of 85% in both NO_x and particulate matter (PM) emissions was necessary to meet the stringent Tier 2 Bin 5 emission levels.

The emission control system was subsequently optimized in the test cell under steady-state and transient conditions. A rapid warm-up strategy was developed to achieve the fastest possible catalyst light-off under cold start conditions. The catalyst performance was mapped and optimized under numerous load and speed conditions with different lean-rich modulation approaches. Finally, diesel particulate filter (DPF) regeneration as well as desulfurization strategies were developed under this project.

Vehicle tests with development emission control systems proved that the combination of low engine-out emissions, in conjunction with a sophisticated regeneration strategy, were able to meet Tier 2 Bin 5 emission levels.