Abstract: Methods and systems are provided for identifying imbalanced cylinder and mitigating the imbalanced cylinder. In one example, a method may include identifying an imbalanced cylinder based on readings from two exhaust gas oxygen sensors positioned upstream and downstream of a catalyst in an exhaust passage, and mitigating the imbalance based on the magnitude of a fault determined from the readings.

Abstract: Methods and systems are provided for identifying and rejecting asymmetric faults that cause engine emissions to be biased rich or lean. In one example, a method for an engine system comprises generating a UEGO sensor feedback set-point adjustment based on slower and faster time components within an outer loop of a catalyst control system; generating an inner-loop bias-offset correction from the slower time component; and indicating degradation of the engine system based on a comparison of the bias-offset correction to a degradation threshold. In this way, the total outer-loop control authority is increased while maintaining drivability and noise, vibration, and harshness (NVH) constraints and meeting emission standards in the presence of an air-to-fuel ratio biasing fault.

Abstract: Methods and systems are provided for detecting an air-fuel imbalance based on output from multiple degradation monitors. In one example, a method comprises, during feedback engine air-fuel ratio control responsive to output of an exhaust gas sensor positioned downstream of a catalyst, indicating a cylinder imbalance responsive to a catalyst transfer function determined only within a specified frequency range based on the exhaust gas sensor output after determining that the catalyst is nominal, and adjusting an actuator in response to the indicated cylinder imbalance. In this way, air-fuel ratio imbalances may be accurately identified and mitigated, thereby reducing emissions.

Abstract: Methods and systems are provided for improving surge detection and mitigation. In one example, a surge detection method may selectively filter an aggregate of temperature-adjusted manifold pressure and boost pressure in a frequency range indicative of surge to reduce the effect of non-minimum phase behavior of throttle inlet pressure on surge detection. In addition, the noise contribution of particular engine actuators on throttle inlet pressure in the selected frequency range may be accounted for, reducing the occurrence of false surge indications.

Abstract: Systems and methods for identifying and mitigating air-fuel imbalance faults specific to an engine cylinder are provided. In one embodiment, a method comprises indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst. In this way, an air-fuel imbalance fault may be accurately detected in a non-uniform exhaust flow so that mitigating actions can be taken, resulting in reduced tailpipe emissions.

Abstract: Methods and systems are provided for detecting an air-fuel imbalance based on output from multiple degradation monitors. In one example, a method comprises, during feedback engine air-fuel ratio control responsive to output of an exhaust gas sensor positioned downstream of a catalyst, indicating a cylinder imbalance responsive to a catalyst transfer function determined only within a specified frequency range based on the exhaust gas sensor output after determining that the catalyst is nominal, and adjusting an actuator in response to the indicated cylinder imbalance. In this way, air-fuel ratio imbalances may be accurately identified and mitigated, thereby reducing emissions.

Abstract: Methods and systems are provided for improving surge detection and mitigation. In one example, a surge detection method may selectively filter an aggregate of temperature-adjusted manifold pressure and boost pressure in a frequency range indicative of surge to reduce the effect of non-minimum phase behavior of throttle inlet pressure on surge detection. In addition, the noise contribution of particular engine actuators on throttle inlet pressure in the selected frequency range may be accounted for, reducing the occurrence of false surge indications.

Abstract: Methods and systems are provided for identifying imbalanced cylinder and mitigating the imbalanced cylinder. In one example, a method may include identifying an imbalanced cylinder based on readings from two exhaust gas oxygen sensors positioned upstream and downstream of a catalyst in an exhaust passage, and mitigating the imbalance based on the magnitude of a fault determined from the readings.

Abstract: Methods and systems are provided for turbine temperature control in an engine system having multiple staged charge boosting devices. In one example, compressed air is provided by a turbocharger compressor until an outlet temperature of the compressor reaches a limit.

Abstract: Methods and systems are provided for turbocharger speed control in an engine system having multiple staged charge boosting devices. In one example, compressed air is provided by a turbocharger compressor until a turbocharger speed reaches a limit.

Abstract: Systems and methods for estimating catalyst transfer function gain are disclosed. In one example, an air-fuel ratio forcing function is applied to a catalyst. Air-fuel ratios upstream and downstream of the catalyst are manipulated to determine a transfer function gain of the catalyst. The transfer function gain may be a basis for indicating the presence or absence of catalyst degradation.

Abstract: Systems and methods for estimating catalyst transfer function gain are disclosed. In one example, an air-fuel ratio forcing function is applied to a catalyst. Air-fuel ratios upstream and downstream of the catalyst are manipulated to determine a transfer function gain of the catalyst. The transfer function gain may be a basis for indicating the presence or absence of catalyst degradation.

Abstract: Systems and methods for identifying and mitigating air-fuel imbalance faults specific to an engine cylinder are provided. In one embodiment, a method comprises indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst. In this way, an air-fuel imbalance fault may be accurately detected in a non-uniform exhaust flow so that mitigating actions can be taken, resulting in reduced tailpipe emissions.

Abstract: Methods and systems are provided for identifying and rejecting asymmetric faults that cause engine emissions to be biased rich or lean. In one example, a method for an engine system comprises generating a UEGO sensor feedback set-point adjustment based on slower and faster time components within an outer loop of a catalyst control system; generating an inner-loop bias-offset correction from the slower time component; and indicating degradation of the engine system based on a comparison of the bias-offset correction to a degradation threshold. In this way, the total outer-loop control authority is increased while maintaining drivability and noise, vibration, and harshness (NVH) constraints and meeting emission standards in the presence of an air-to-fuel ratio biasing fault.