The paper presents a study on the influence of increased rail pressure on the flow field of an injector nozzle at pressures of up to 3200 bar. Additionally the influence of nozzle conicity, HE-Rounding and nozzle-hole-diameter on the injector flow was investigated with CFD calculations. In these calculations the real behaviour of the nozzle movement was considered. The nozzles were tested on a special single cylinder research engine. The results showed high potential to fulfill EURO VI emission standards by raising the injection pressure and by optimizing the nozzle geometry, without exhaust aftertreatment measures.