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Exhaust gas recirculation is an effective means to reduce NOx-emissions of Diesel engines. Unfortunately too high EGR rates increase the emissions of hydrocarbons, carbon monoxide and soot. So EGR has to be controlled precisely. The paper describes an EGR-system for Diesel engines which senses the air-flow and the fuel-flow of the engine and limits the EGR-rate so, that the air-fuel-ratio is lean enough for a clean combustion. Furthermore the paper shows the emission results which have been obtained with the described EGR-system on different Diesel passenger cars.

Passenger car DI Diesel engines need a flexible fuel injection system. Bosch develops a common rail system for this purpose. Besides variation of fuel quantity and start of injection, it permits to choosing freely injection pressure inthe rangeof 150 to 1400 barand injecting fuel in several portions. These new means will contribute to further improvements of DI engines concerning noise, exhaust emissions and engine torque.

The particulate emissions can be reduced by increasing injection pressure. The NOx-emission can be lowered to the required amount with a retarded injection-begin. These measures raise fuel consumption by approximately 8-10 %. To avoid blue smoke from the cold engine, it is advantageous that the fuel injection is advanced during the warm-up period. These statements apply for injection systems with unit injectors as well as for pump-line-nozzle-systems. In this paper, the pump-line-nozzle-system will be described. With this system, injection pressures of 1200 to 1400 bar at the injection nozzle are reached. The injection-begin can be changed with a control-sleeve in-line pump. The injection-begin and fuel quantity can be flexibly and accurately adjusted by means of an electronic governor.