Abstract: A method for improving a purge conversion efficiency of a Lean NOx Trap coupled downstream of a lean-burn internal combustion engine is presented. This method recognizes that during a purge of the LNT, its temperature increases due to the exothermic reactions in the LNT. Once the LNT temperature exceeds a certain threshold, further increases lead to a reduction in the NOx storage capacity, and therefore an increase in NOx emissions during the purge of the LNT. Therefore, it is proposed to cool the LNT temperature once the threshold is exceeded. This method improves emission control and fuel economy during purge.

Abstract: A method for improving a purge conversion efficiency of a Lean NOx Trap coupled downstream of a lean-burn internal combustion engine is presented. This method recognizes that during a purge of the LNT, its temperature increases due to the exothermic reactions in the LNT. Once the LNT temperature exceeds a certain threshold, further increases lead to a reduction in the NOx storage capacity, and therefore an increase in NOx emissions during the purge of the LNT. Therefore, it is proposed to cool the LNT temperature once the threshold is exceeded. This method improves emission control and fuel economy during purge.

Abstract: An exhaust control system for an automotive internal combustion engine having an exhaust system that includes a NOx adsorber to trap and reduce NOx emissions from the engine. The engine is operated using an air/fuel ratio that alternates between lean and rich, with the adsorber storing NOx during the lean periods of combustion and catalytically reducing the NOx during the rich periods of combustion. The system determines the amount of NOx stored in the adsorber using upstream and downstream O2 sensors. The release of stored NOx and O2 at the beginning of the rich regeneration causes a delay between switching of the sensors. The system determines how much of this delay is due to the release of stored O2 and subtracts that amount from the total delay. There is also a switching delay at the beginning of each lean period due to the storage of O2 in the adsorber.