Abstract
The paper discusses the challenges that diesel engines are facing in view of the newly proposed Tier 2 Emission Standards for light-duty vehicular applications. These Standards will be enacted in 2004 and they represent the most sweeping emission legislation so far. They are fuel neutral, which implies that the same limits have to be met by both gasoline and diesel powered engines. For diesel powered vehicles the development required to meet the new standards requires an optimization approach, where engine, fuel and aftertreatment devices are developped as a system to obtain the lowest tailpipe emission levels. The development of catalytic aftertreatment shows promise but the technologies are sulfur sensitive. In order to maximize the potential of aftertreatment technology, sulfur in diesel fuel must be reduced to ultra-low levels.