In a turbocharged internal combustion engine system including an eCompressor as a secondary air pump (SAP) for injecting air into an exhaust system of the ICE, controllable valves enable the turbocharger compressor and the SAP to provide two-stage compressed air to the intake of the ICE in certain operating conditions, or to feed the air via a secondary air injection line (SAI line) into the exhaust system in other conditions. A conduit is tapped off the discharge of the SAP and connects with discharge ducting from the turbocharger compressor, and an on/off valve configured for defined leakage in the “off” position controls flow through the conduit. When the air from the SAP is needed only for injection air, the leakage through the leaky valve into the intake system suppresses surge of the SAP.

Methods and systems are provided for determining changes in a flow area of an exhaust gas recirculation (EGR) valve for EGR flow estimates due to soot accumulation on the EGR valve. In one example, a method includes indicating soot accumulation on the EGR valve based on a difference in EGR flow estimated with an intake oxygen sensor and with a pressure sensor coupled across the EGR valve. The determination of the difference of the EGR flow estimates may occur when the engine is not boosted.

Methods and systems are provided for determining changes in a flow area of an exhaust gas recirculation (EGR) valve for EGR flow estimates due to soot accumulation on the EGR valve. In one example, a method includes indicating soot accumulation on the EGR valve based on a difference in EGR flow estimated with an intake oxygen sensor and with a pressure sensor coupled across the EGR valve. The determination of the difference of the EGR flow estimates may occur when the engine is not boosted.

The present disclosure relates to dual compression engine boosting systems utilizing both a turbocharger and a supercharger and control systems relating to relative activation and deactivation of the boosting devices. Various Exhaust Gas Recirculation (EGR) configurations are also disclosed for the dual compression engine boosting systems.

The present disclosure relates to dual compression engine boosting systems utilizing both a turbocharger and a supercharger and control systems relating to relative activation and deactivation of the boosting devices. Various Exhaust Gas Recirculation (EGR) configurations are also disclosed for the dual compression engine boosting systems.

Methods and systems are provided for an engine including a humidity sensor. Degradation of the humidity sensor may be determined based on a change in intake air relative humidity as compared to a change in intake air temperature or pressure, under selected conditions. An amount of exhaust gas recirculated to an engine intake is adjusted differently based on whether the humidity sensor is degraded or functional.

Methods and systems are provided for an engine including a humidity sensor. Degradation of the humidity sensor may be determined based on a change in intake air relative humidity as compared to a change in intake air temperature or pressure, under selected conditions. An amount of exhaust gas recirculated to an engine intake is adjusted differently based on whether the humidity sensor is degraded or functional.

Methods are provided for identifying degradation in components of a compressor recirculation valve (CRV). One method may include inferring degradation of the CRV based on adaptation of a compressor surge line outside an expected range.

Methods are provided for identifying degradation in components of a compressor recirculation valve (CRV). One method may include inferring degradation of the CRV based on adaptation of a compressor surge line outside an expected range.

Embodiments for diagnosing a humidity sensor are provided. One example method comprises, responsive to a humidity sensor test cycle, pumping air conditioning and windshield washer gas flows past a humidity sensor, and indicating humidity sensor degradation based on a response of the humidity sensor to the air conditioning and windshield washer gas flows. In this way, degradation of the humidity sensor may be indicated if the humidity sensed by the humidity sensor does not change responsive to the humidity sensor test cycle being initiated.