Even though Extrusion is often regarded as a semi stationary process, the defor- mations of the die at the beginning of the process can have great influence on the process later on. During filling of the die, the deformation of the die depends on the location of the flow front up to a point where parts of the profile will be opened or closed, especially in porthole dies. In this paper we present an accurate 2D method to simulate the filling of extrusion dies. The method is based on the pseudo concentration technique. We compare different options to model the pseudo material and choose the best.