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Catalytic performance can be improved by reducing bulk density (BD) and increasing geometric surface area (GSA) of ceramic substrate. Ultra thin-wall / high cell-density ceramic substrates, such as 3 mil/ 600 cpsi and 2 mil/ 900 cpsi have improved the catalytic performance over the conventional 6 mil/ 400 cpsi substrates. and are expected to help in complying with future emission regulations, as well as catalyst down-sizing. This paper describes the effects of BD and GSA using Pd-based catalysts. The significant reduction of hydrocarbons emissions was demonstrated at close-coupled location, and dual bed design was proven effective. The effectiveness at under-floor location was not as significant as the close-coupled location. This paper proposes the converter layout of dual bed close-coupled converter consisting of small volume 2 mill 900 cpsi front catalyst and large volume 3 mil/ 600 cpsi rear catalyst.

New ultra-low vehicle emission legislation requires advanced catalyst systems to achieve high conversion requirements. Manufacturers have to improve both the washcoat formulations and the catalyst substrate technology to meet these new regulations. This paper will present the results of a computer modeling study on the effects of ultra-thinwall catalysts on hydrocarbon and carbon monoxide light-off performance improvement. The experimental data from catalyst light-off testing on an engine dynamometer are compared with theoretical results of advanced substrate modeling for ultra-thin wall ceramic substrates. Results show that thermal mass has the greatest effect on light-off performance. Decreases in wall thickness offer the greatest benefit to light-off performance by lowering the thermal mass of the substrate, thus allowing it to reach light-off temperature faster.