Method for operating a combustion engine system

A combustion engine system, comprising:

• a combustion engine that produces exhaust gas when in operation,
• a fresh air system for feeding fresh air to the combustion engine and an exhaust gas system for dissipating exhaust gas,
• an exhaust gas turbocharger including a compressor wheel incorporated in the fresh air system for compressing the fresh air and a turbine wheel incorporated in the exhaust gas system for driving the compressor wheel,
• an adjustable waste gate valve of the exhaust gas turbocharger, the waste gate valve adjustable between a closed position and a bypass position and when in the bypass position guides exhaust gas via a bypass channel past the turbine wheel,
• a pollutant conversion system incorporated in the exhaust gas system for reducing pollutants in the exhaust gas,
• a variable turbine geometry of the exhaust gas turbocharger, the variable turbine geometry including a plurality of adjustable guide elements surrounding the turbine wheel in a circumferential direction, the plurality of guide elements structured and arranged to follow one another in the circumferential direction and define an overall cross-section in their respective position for the exhaust gas to flow through,
• a control system, the control system being communicatively connected to the exhaust gas turbocharger,
• wherein the control system is configured to, in a control mode where the pollutant conversion system comprises a temperature above a threshold temperature, adjust the plurality of guide elements such that the overall cross-section is between a control minimum value and a control maximum value, and
• wherein the control system is further configured to, in a heat-up mode at temperatures of the pollutant conversion system below the threshold temperature, move the plurality of guide elements into a heat-up position where the overall cross-section is smaller than the control minimum value, wherein during a change-over from the heat up mode to the control mode, adjusting the variable turbine geometry into an idling position where the guide elements expose a gap to reduce exhaust gas counter-pressure.