Powertrains with internal combustion engines are essential for the implementation of the mobility transition and the global reduction of CO2 emissions. In this work, development focus within the powertrain system is on enhancing the combustion process of the engine as it provides a significant proportion of the work required to propel the vehicle and is by far the weakest link in the efficiency chain of the powertrain and thus bears high potential to improve overall efficiency. In this respect, the paper discusses in detail the development of an internal combustion engine concept that is designed to achieve high efficiencies, aiming at a brake thermal efficiency (BTE) of significantly more than 40% in a considerable map range and high peak efficiency with acceptable Noise, Vibration and Harshness (NVH) performance. The study describes an advanced Turbulent Jet Ignition (TJI) system that comprises active control of the air-fuel mixture within the Pre-chamber depending on the operating conditions and thus enables high dilution rates of up to 42% by externally cooled and recirculated residual gas. The latter allows for a distinct increase of the compression ratio to 14.8 which – along with a combustion system optimization – ultimately results in BTE gains in mid high-load by up to 2%pts compared to passive TJI baseline engine. In parallel, the system enables to keep very good engine stability at high Exhaust Gas Recirculation (EGR) dilution rates and enables to match the reference engine power density of 73 kW/l at rated power operating point, with the latter attributed to improved knock mitigation potential. Furthermore, the active TJI system allows to stabilize the engine operation around the EGR dilution limits compared to passive TJI, suggesting that operation and final engine calibration closer to optimum BTE point is possible. Preliminary tests also demonstrate an improved late combustion tolerance compared to passive TJI system, an important indicator for good emissions performance in cold conditions.