To fulfill the demands for a future diesel engine in terms of Emission compliance, CO2 emissions, performance and cost effectiveness also sets new requirements for the development process. This paper focuses on the development of the diesel combustion system to comply with Euro 6d including real driving conditions (RDE) with emphasis on the novel methods applied throughout the process. The foundation of a high performing system is formed by first determining the requirements for the system, after which the key factors that affect system performance are selected. Based on the requirements a robust charge motion with desired flow characteristics is defined. Then, a new effective automated direct driven Combustion CFD optimization for combustion chamber and spray is developed. From the simulation pareto fronts, the best hardware solutions are selected. These candidates are selected with different attributes. An increase in knowledge is gained by looking into the details in the simulation result for these candidates. These are then verified by creating rapid prototypes for evaluation. The development of a highly automated test scheme makes it possibly to model the results based on the physical testing. Using the modeled data creates the possibility for high modularity. Hence, it is possible to reduce the number of development loops when creating combustion system variants for different requirements. The result is a robust modular combustion system that has significant improvement in efficiency in combination with an all-new injection strategy.