Modern internal combustion engines are being developed to provide the requested performance, to be efficient and to comply with strict exhaust emission standards. One of the main engine components, which has a direct impact on all, performance, efficiency and emissions is the fuel injector. Understanding the fluid flow behavior inside a fuel injector, and its nozzle, is therefore of high importance. Experimental investigations are expensive and difficult to performed due to the small nozzle size and short duration of fuel injection events. A numerical simulation on the other hand offers a fast and inexpensive way to analyze the behavior of the nozzle interior flow for a variety of prototype geometries and operating conditions.