The ever increasing complexity of engine control systems demands upon the application of new tools and methodologies. For the online optimisation of diesel engines on test beds a number of aspects have to be considered and optimised in parallel to achieve the best compromise for emissions, performance, NVH, etc. For this complex development process Design of Experiments (DoE) is only a first step to be performed. By its implementation into the test bed software the complex process can be effectively handled online. Additional software tools are combined in this development process to exploit the entire potential of HSDI engine control systems with the additional benefit of reducing in parallel the engine development time. Examples of a successful application of these methodologies in series development projects and the results hence achieved are presented.