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Within the next decade, all light-duty vehicles in the United States will be required to meet Tier 2 or LEV 2 tailpipe emission standards. As emission standards have tightened over time catalyst systems have increased in cost. The factors that have contributed to the growth in cost include increases in both precious metal content and catalyst volumes. Calibration strategy, catalyst, and substrate technology improvements have also enabled previous emission standards to be met. The recent dramatic fluctuations in precious metal price, coupled with the increasing desire to reduce system cost, have led catalyst companies to develop converter technologies containing decreasing amounts of precious metal, and still meet Tier2/LEV2 standards. In this paper the development of a novel, near base metal, catalyst technology is described. The effects of precious metal support type and catalyst preparation method are reported using model engine bench and vehicle tests.

A computer model is successfully used to predict emissions from a vehicle, fitted with a catalyst, over a standard driving cycle (the U.S. FTP cycle). Kinetic expressions to describe the catalyst's activity are derived from laboratory measurements. A study showing the effect of changing the precious metal loading of the catalyst on the activity of the catalyst is presented. The impact on model parameters is derived and the model is successfully used to predict the effect of changing precious metal loading on vehicle performance over the FTP cycle. The results indicate the model can be a useful tool in exhaust system design.