DEUTZ has developed a new TCD 3.9 and TCD 4.0 engine series for use in mobile machinery and other non-road applications. This engine replaces the established TCD 3.6 and TCD 4.1 engines. Care was taken to ensure that the TCD 3.9/4.0 is compatible with the TCD 3.6. Due to the increased displacement, increased peak pressure, high turbocharger efficiency and the elimination of exhaust gas recirculation, the output can be increased to 130 kW, thus exceeding the values of the predecessor TCD 4.1, which has a larger displacement. In the process, both engine dynamics and fuel consumption could be improved. Considering the cost targets, an OHV engine was designed with two valves per cylinder without sacrificing thermodynamic targets. This gives the potential for future variability of the valve train. Furthermore, the power take-off interfaces (PTO) commonly used for industrial engines are present. Initially, the engine will be developed for EU Stage V and US EPA/CARB Tier 4 emission standards. The high-performance SCR system allows the engine to be tuned to save fuel consumption without the use of exhaust gas recirculation. In terms of design, the engine has been prepared for the installation of additional components that are required to comply with future emission standards such as the announced CARB Tier 5.