Diesel engines continue to offer outstanding benefits in fuel consumption and durability over other engine types. Recently however, the environmental impact of diesel engines has become an increasingly critical factor and has a significant influence on diesel engine development trends. The fuel injection system is one of the most important keys to fulfill the stringent exhaust emissions standards while still maintaining the fuel economy and related CO2 emission benefits of the diesel engine.Research has shown that, to a significant extent, by using the technique of fuel preinjection, DI diesel engines can simultaneously reduce NOx levels and particulate emissions while also improving the level of combustion noise. In addition, the technique has demonstrated the possibility to address these environmentally-focused goals while maintaining low fuel consumption, a characteristic strength of diesel engines, which is directly related to the reductions in CO2 emissions. Since all of these important environmental factors are significantly influenced by the fuel injection system characteristics, it will undoubtedly play a dominant role in successful future diesel engine development.This paper outlines and describes potential improvements in combustion and exhaust emission characteristics through the application of injection rate shaping and pilot fuel injection. These improvements will be analyzed for many applications using a prototype injection system with advanced hydraulic performance. Furthermore, it will show how pilot injection should be performed in order to get both a reduction of exhaust emissions and combustion noise. Finally, the potential for optimizing engine behavior, through variation of these injection system characteristics, will be discussed.