Abstract: A method for selecting one of first and second cylinder groups of an internal combustion engine is provided. The first and second cylinder groups are coupled with first and second catalytic converters, respectively. The method includes identifying one of the first and second catalytic converters by comparing first and second catalyst parameters, associated with the first and second catalytic converters, respectively, to one another. The first and second catalyst parameters indicate which one of the catalytic converters is more capable of maintaining reduced emissions while adjusting an engine operational parameter. The method further includes selecting one of the first and second cylinder groups coupled to the identified catalytic converter for changing an engine operational parameter in the selected cylinder group.

Abstract: A method for selecting one of first and second cylinder groups of an internal combustion engine is provided. The first and second cylinder groups are coupled with first and second catalytic converters, respectively. The method includes identifying one of the first and second catalytic converters by comparing first and second catalyst parameters, associated with the first and second catalytic converters, respectively, to one another. The first and second catalyst parameters indicate which one of the catalytic converters is more capable of maintaining reduced emissions while adjusting an engine operational parameter. The method further includes selecting one of the first and second cylinder groups coupled to the identified catalytic converter for changing an-engine operational parameter in the selected cylinder group.

Abstract: A method for selecting one of first and second cylinder groups of an internal combustion engine is provided. The first and second cylinder groups are coupled with first and second catalytic converters, respectively. The method includes identifying one of the first and second catalytic converters by comparing first and second catalyst parameters, associated with the first and second catalytic converters, respectively, to one another. The first and second catalyst parameters indicate which one of the catalytic converters is more capable of maintaining reduced emissions while adjusting an engine operational parameter. The method further includes selecting one of the first and second cylinder groups coupled to the identified catalytic converter for changing an engine operational parameter in the selected cylinder group.

Abstract: A method for controlling the phasing of first and second air/fuel ratio oscillations in first and second cylinder groups, respectively, of an internal combustion engine is provided. The method includes determining a phase difference between the first air/fuel ratio oscillations and the second air/fuel ratio oscillations. The method further includes adjusting a phase of the first air/fuel ratio oscillations so that both first and second air/fuel ratio oscillations are at a predetermined phase offset with respect to one another, while maintaining an average air/fuel bias in the first cylinder group.

Abstract: A method for controlling first and second air/fuel ratio oscillations in first and second cylinder groups, respectively, of an internal combustion engine is provided. The method includes determining a first frequency of the first air/fuel ratio oscillations in the first cylinder group. The method further includes determining a second frequency of the second air/fuel ratio oscillations in the second cylinder group. Finally, the method includes adjusting the first frequency towards the second frequency responsive to a frequency difference between the first and second frequencies.

Abstract: A control system and method is provided for selecting one of first and second cylinder groups of an internal combustion engine when a frequency of air/fuel ratio oscillations in the selected cylinder group is to be adjusted. The method includes determining which of first and second frequencies of air/fuel ratio oscillations in the first and second cylinder groups, respectively, has a greater frequency. Further, the method includes selecting one of the first and second cylinder groups having the greater frequency of air/fuel ratio oscillations. The selection is made to reduce engine torque fluctuations when changing a frequency of air/fuel ratio oscillations in the selected cylinder group.

Abstract: A method and system for diagnosing catalyst operation in an internal combustion engine having a two-bank, three EGO sensor structure includes monitoring when the EGO sensors switch states between rich and lean and determining the ratio between a switch count of the post-catalyst EGO sensor signal and a switch count of a pre-catalyst EGO sensor signal over a selected time period. If the exhaust bank is a one-sensor bank having only a post-catalyst EGO sensor and not a pre-catalyst EGO sensor, the system uses the switch count from the pre-catalyst EGO sensor in the two-sensor bank to calculate the switch ratio, thereby allowing calculation of two switch ratios without two matched pairs of EGO sensors. The switch ratio indicates the efficiency of the catalyst and may be compared with later-generated ratios to monitor converter efficiency over time.

Abstract: A method and system for diagnosing catalyst operation in an internal combustion engine having a two-bank, three EGO sensor structure includes determining the ratio of the arc length between the post-catalyst EGO sensor signal and the arc length of a pre-catalyst EGO sensor signal over a selected time period. If the exhaust bank is a one-sensor bank having only a post-catalyst EGO sensor and no pre-catalyst EGO sensor, the system uses the arc length from the pre-catalyst EGO sensor in the two-sensor bank to calculate the arc length ratio, thereby allowing calculation of two arc length ratios without two matched pairs of EGO sensors. The ratio indicates the efficiency of the catalyst and may be compared with calibratable or experimentally-determined thresholds to monitor converter efficiency over time.

Abstract: A method and system for adjusting a fuel injection amount in one of two groups of cylinders in an internal combustion engine using feedback signals generated by oxygen sensors coupled to both groups of cylinders. The claimed invention includes first and second groups of engine cylinders coupled to first and second exhaust banks respectively. The first exhaust bank includes a catalyst and at least a pre-catalyst EGO sensor for generating a first feedback signal. The second exhaust bank includes a catalyst and a post-catalyst EGO sensor for generating a second feedback signal. A controller calculates desired air/fuel ratio values for the first group of cylinders based on the first feedback signal. The controller also calculates desired air/fuel ratio values for the second group of cylinders based on the first feedback signal and the second feedback signal. The controller adjusts the level of liquid fuel injected into the groups of cylinders based on the calculated air/fuel ratio values.

Abstract: A method and system for diagnosing catalyst operation in an internal combustion engine having a two-bank, three EGO sensor structure includes determining the ratio of the arc length between the post-catalyst EGO sensor signal and the arc length of a pre-catalyst EGO sensor signal over a selected time period. If the exhaust bank is a one-sensor bank having only a post-catalyst EGO sensor and no pre-catalyst EGO sensor, the system uses the arc length from the pre-catalyst EGO sensor in the two-sensor bank to calculate the arc length ratio, thereby allowing calculation of two arc length ratios without two matched pairs of EGO sensors. The ratio indicates the efficiency of the catalyst and may be compared with calibratable or experimentally-determined thresholds to monitor converter efficiency over time.

Abstract: A method and system for controlling the air/fuel ratio in an internal combustion engine having first and second groups of cylinders coupled to first and second exhaust banks, respectively. The first exhaust bank includes a catalyst and at least a pre-catalyst oxygen sensor. The second exhaust bank includes a catalyst and no more than one post-catalyst oxygen sensor. The oxygen sensors monitor the oxygen content of the exhaust gases in their corresponding exhaust banks and provide feedback signals to a controller. The controller uses the feedback signal from the pre-catalyst oxygen sensor (in the first bank) to calculate desired A/F values in the first group of cylinders. The controller uses both the feedback signal from the pre-catalyst oxygen sensor (in the first bank) and the feedback signal from the post-catalyst oxygen sensor (in the second bank) to calculate desired A/F values for the second group of cylinders.

Abstract: A method and system for controlling the air/fuel ratio in an internal combustion engine having first and second groups of cylinders coupled to first and second exhaust banks, respectively. Each exhaust bank has a catalyst, a pre-catalyst oxygen sensor and a post-catalyst oxygen sensor, wherein the oxygen sensors monitor the air/fuel ratio in their respective exhaust banks and provide corresponding feedback signals to a controller. The controller uses the feedback signals to control the air/fuel ratio in the engine cylinders. When it is detected that one or the other of the pre-catalyst oxygen sensors has degraded, the controller calculates A/F values for the group of cylinders corresponding to the exhaust bank having a degraded EGO sensor based on feedback signals from the three still-functional oxygen sensors.

Abstract: A method and system for controlling the air/fuel ratio in an internal combustion engine having a first group of cylinders and a second group of cylinders. The first group of cylinders is coupled to a catalyst and at least one oxygen sensor, which provides a first feedback signal. The second group of cylinders is coupled to a catalyst and a post-catalyst oxygen sensor, which provides a second feedback signal. A controller uses the first and second feedback signals to calculate a short-term air/fuel bias value for the second group of cylinders. The controller also calculates a new long-term air/fuel bias value corresponding to the current engine speed and engine. The new long-term air/fuel bias value is based on a previously-calculated long-term air/fuel bias value calculated for the same engine load and speed. A total air/fuel bias value is calculated based on the short-term air/fuel bias value and the long-term air/fuel bias value. The new long-term air/fuel bias value is stored for future calculations.