In an exhaust gas turbocharger system for charging an engine including a compressor arrangement at a charging fluid side LL and a turbine arrangement at an exhaust gas side AG, a further compressor which is driven by a separate controllable drive and whose primary side is connected to the charging fluid side LL while its secondary side is connected to the exhaust gas side is provided for compressing charge air taken from the charging fluid side and supply it to the exhaust gas side for assisting driving the exhaust gas turbines so as to maintain them at relatively high speeds in transition periods including engine idling.