Thermodynamic powertrains are imperative for the implementation of the mobility transition and the global reduction of CO2 emissions. Specifically, hybrid powertrains with high efficiency internal combustion engines are an important contributor in the race to reduced CO2 emissions in the transport sector and help the OEM to undercut future CO2 fleet targets when pure BEV´s do not find sufficient market penetration. In this work, development focus within the powertrain system is on enhancing the combustion process of the engine as it 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 achieving very high efficiencies in a wide area of the operating conditions and outstanding peak efficiency. The special feature of this concept is an enhanced 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 extreme dilution rates with externally cooled and recirculated residual gas. The latter allows for a distinct increase of the compression ratio which – along with a dedicated combustion chamber layout – ultimately results in significant efficiency gains. The paper will discuss in detail the development of the engine and combustion system around the TJI concept and finally present testing and validation results of the 4-cylinder prototype engine.