Simulation using basic acoustic 2-port elements is a time effective method for prediction of the attenuation of single components as well as of complete exhaust aftertreatment and silencer systems. However, with the complexity of current systems, the transformation from design geometries to networks of basic elements is not straightforward. In this paper a practical example of the modelling of a modern exhaust aftertreatment system is presented.A silencer aimed at the Euro 6 heavy duty emissions legislation containing complex flow turnings, parallel branches, DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter) and SCR (Selective Catalytic Reduction) catalysts was modelled. Evaluation against measurements in order to understand the influence of the different acoustic elements upon overall attenuation and to improve the model with respect to near field and higher order mode effects was done. With the resulting accuracy, the 2-port model still, despite the geometrical complexity, offers a tractable tool for analysis and design of complete exhaust system in order to gain insertion loss either by modifying existing elements or by adding new.