In 1993 STEYR Nutzfahrzeuge AG concluded the EURO 2 development of engines of the WD 615 series. Medium-duty engines are still in the process of development. The task set specified that only conventional, well-proven mechanical components should be used. To reduce NOx swirl intensity was lessened. For fuel injection the S 3000 was changed to the S 7100 and the number of nozzle-holes was raised from 5 to 7. By the use of return-flow throttling valves the pressure immediately before the injector nozzles could be significantly increased without any additional mechanical loading on the injection pump or its drive. The interdependent geometry of the combustion chamber and nozzles was calculated by was calculated by computer programs developed in the company. The injection timing was delayed; the pump element was given an advanced injection edge largely to avoid problems when starting cold. In spite of more gentle combustion the airborne sound level rises as a result of the increased mechanical loading. In this point measures were also taken so that the new engines and vehicles could receive the low-noise homologation category. To further reduce exhaust emission in line with EURO 2 the use of electronics will be indispensable and the agents oil and fuel will also have to be further optimised. It is even possible that technologies which today sound exotic, such as water injection, will be used. (A)
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