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Beside the fuel consumption reduction the emission reduction is one of the main development objectives. The oncoming increasingly stringent emission limits demand improvements to the emission level especially in the cold start and engine warm-up phase when the catalyst is still inactivate. In this phase it is necessary to produce raw emissions on a very low level and to reach the catalyst light-off temperature as fast as possible using a suitable injection strategy. In this paper the potentials and risks of injection strategies for efficient catalyst heating (lean warm-up without secondary-air pump) with piezo and solenoid GDI combustion systems, in side and central mounting position, are introduced. The main emphasis is to obtain low HC emissions and high exhaust heat flow with acceptable engine smoothness by deriving suitable tuning parameters. During the investigations the various degrees of freedom of the applied GDI Engine were used in the best possible way.

In modern passenger car diesel engines, multiple injection, MI, and rate shaping are measures, which in conjunction with others help to achieve the emissions legislation EU6 and US Tier2 Bin5. However, where hitherto mainly pollutant emissions where considered, CO2 output - i.e. fuel consumption - becomes increasingly important. Also, off cycle emissions may have to be regarded in the future. Additionally engine noise and drivability need consideration. The complexity and effect of an applied injection strategy is defined by the overall engine concept including the after treatment system, and also by the vehicle inertia. Additionally a modern fuel injection system not only has to allow for the necessary injection strategies but at the same time needs to offer robust performance over life time.