Abstract: A method for determining the efficiency of a three-way catalyst is presented. It is shown that more accurate results are achieved if the efficiency estimates are performed when the engine is at idle or during low load operating conditions. The efficiency is inferred from the amount of fuel required to purge the device after it has been fully saturated with oxidants due to lean operation. Due to improved accuracy and reduced reductant waste, this method allows for improved emission control and fuel efficiency.

Abstract: A method for monitoring efficiency of an exhaust gas aftertreatment device is presented. The efficiency is inferred from the amount of fuel required to perform purge of the device after it has been saturated with exhaust gas components such as NOx and oxygen to a predetermined level. The level of saturation is determined from the amount of tailpipe emissions as indicated by the tailpipe exhaust gas sensor. This method improves precision in determining device efficiency and therefore eliminates unnecessary sulfur purges and improves fuel economy. Also, better emission control is achieved since the tailpipe exhaust gas sensor allows closed loop monitoring of NOx emissions and prevents the device from overfilling.

Abstract: A method for determining the efficiency of a three-way catalyst is presented. It is shown that more accurate results are achieved if the efficiency estimates are performed when the engine is at idle or during low load operating conditions. The efficiency is inferred from the amount of fuel required to purge the device after it has been fully saturated with oxidants due to lean operation. Due to improved accuracy and reduced reductant waste, this method allows for improved emission control and fuel efficiency.

Abstract: An improved method for monitoring an efficiency of a three-way catalyst coupled in an exhaust passage of an internal combustion engine is presented. First, a reference efficiency estimate (shortly after a SOx purge) is generated based on several data points obtained during normal vehicle driving conditions over varying device temperatures. Next, a current efficiency estimate is obtained from several data points. The two estimates are compared to obtain a measure of reduction in the catalyst efficiency due to device sulfation.

Abstract: A more precise method for determining the oxygen storage capacity of an exhaust gas aftertreatment device is presented. The most accurate capacity estimate is obtained while the engine is idling or during low load operation. The capacity is determined by integrating the output of an oxygen sensor located downstream of the device during a period of time that it takes to store more than a predetermined amount of oxygen in the device. The overall LNT efficiency can then be inferred from its oxygen storage capacity. This method allows for improved emission control and fuel economy.

Abstract: A method for estimating the amount of NOx stored in a lean NOx trap. The method includes determining a change in the oxygen concentration between an exhaust air/fuel ratio entering the lean NOx trap and exiting the lean NOx trap to determine the amount of NOx absorbed in the trap and correcting such determination for water gas shift reaction effects in such change in oxygen concentration determination.

Abstract: A method and apparatus for determining the capacity of a trap to store NOx based on the change in oxygen storage in the trap occurring as a result of sulfation of the trap.