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The internal combustion engines, and the heavy duty truck diesel engines in particular, are facing a severe challenge to cope with the upcoming stringent emission legislation world-wide. To comply with these low limits, engine internal measures must be complemented with exhaust gas aftertreatment systems with sophisticated electronic control. A reduction of NOx and particulate emission of more than 90% is required. Various strategies to comply with Euro 4, 5 and US 2007 are discussed, also in view of engine performance, fuel economy and cooling system load. Recommendations are given for the most suitable approach to comply also in future with emission legislation in Europe and the United States.

Despite the increasingly stringent emissions legislation, users and owners of commercial diesel vehicles are continually demanding that each new engine generation is more economical than the previous one. This is especially important for commercial vehicles where the majority of engines are in the 1-2ltr./cyl. class. The demands are being reflected in new engine designs with lower friction and improved structural stiffness, together with fuel systems having increased pressure capability, higher spill rates, injection rate shaping and advanced control features. These fuel system requirements have led to a variety of new fuel injection systems and in the search for increased injection pressure these fuel systems have placed greater demands on the engine, especially in areas such as the cylinder head and fuel system drive, sometimes with adverse effects on the combustion and fuel injection system induced mechanical noise.

The paper reports on achievements obtained in an ongoing development program which is part of a european EUREKA joint research project named EFFLED (EFFicient Low Emission Diesel) being performed at AVL in cooperation with the companies DAF Trucks, Serck Heat Transfer, Robert Bosch and the Community of the City of Rotterdam. The main objective of this project is the development and refinement of a venturi supported exhaust gas recirculation (EGR) system for a turbocharged and intercooled heavy-duty (HD) diesel engine enabling map controlled cooled EGR rates which are high enough to achieve future low NOx emission standards at acceptable fuel consumption level. In addition to EGR, further technologies have been investigated, which may be required to meet future exhaust emission standards.