OBD-II Performance of Three-Way Catalysts

The current method for on-board monitoring of catalyst performance involves detecting the degradation in the oxygen storage capacity as the catalyst ages. Inherent in this method is the need to correlate the deactivation in HC perform-ance with oxygen storage capacity. However, as HC standards become more stringent, light off becomes the key factor impacting HC emission levels, and it is increasingly difficult to detect failures in HC performance based on OSC deactivation. A possible approach to address this challenge is to include catalyst formulation as a variable in performing OBD-II calibrations. This study explores the potential for tailoring the OBD-II performance of a catalyst by customizing the PGM/OSC component to give the desired degree of thermal stability. The effects of sulfur and aging conditions are also investigated. The potential for independent adjustment of OSC and HC performance is discussed.