POWER TRAIN SYSTEM

To provide a novel power train system capable of improving fuel efficiency, reducing harmful components of an exhaust gas, and improving an output by adjusting a composition of a gas component of the exhaust gas in accordance with an operation condition. Therefore, provided is a power train system including a gas component separation unit (2) which extracts a plurality of gas components having different specific heat ratios from an exhaust gas of a spark ignition type internal combustion engine (1), a recirculation unit which recirculates the plurality of gas components to a combustion chamber of the internal combustion engine, and a ratio adjustment unit (3) which adjusts a ratio of the plurality of gas components recirculated to the combustion chamber in response to an operation state of the internal combustion engine. A composition of a gas recirculated to the internal combustion engine can be adjusted depending on various operation conditions. Accordingly, it is possible to improve fuel efficiency, reduce harmful components of an exhaust gas, and improve an output in a wide range of operation conditions of the internal combustion engine.