New EU and US emissions regulations require the development of advanced after- treatment systems for non-road diesel engine exhausts. To help develop these at Liebherr Machines Bulle, the use of CFD has been adopted. The pro ject used two main models: one for the dosing of fuel for the regeneration of the Diesel Particulate Filter (HC Doser model) and one for the Selective Cataylitic Reduction system (SCR model). The HC Doser model was validated against published data and in-house experimental results. Good agreement was found in all cases. The SCR model was validated against published data only, showing good qualitative agreement -spatial distribution and spray formation- but the quantitative measures - N H3 and H N N C O concentrations- still need further adjustment. Validation against in-house experimental results was not possible as the necessary experiments have not yet been carried out. After validation, the DPF model was used to evaluate and improve specfic exhaust geometry configurations at LMB. Selected case studies are presented to show the appli- cability of the models to the design process, and the derived advantages. Using the DPF model, basic research was undertaken to investigate the ifluence of the static mixer's geometry on the performance of the system during regeneration. A new mixer geometry was designed which reduced the pressure drop and increased the uniformity of the HC distribution