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Catalytic performance can be improved by reducing heat capacity and increasing geometric surface area (GSA). The effects of the catalyst layout and the substrate cell structure were investigated on the catalytic performance. The catalyst layout covers an under-floor catalyst only, a close-coupled catalyst with an under-floor catalyst and a close-coupled catalyst only, and a dual-bed close-coupled catalyst only. The substrate cell structure covers from conventional 6 mil/ 400 cpsi substrate to the ultra thin-wall and high cell-density substrate of 2 mil/ 900 cpsi. Significant reduction of emissions can be achieved by moving the catalyst location upstream of the exhaust gas and combined with using the ultra thin-wall and high cell-density substrates. Furthermore, dual-bed design demonstrated further improvement of catalytic performance at close-coupled location.

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.

Catalytic performance can be improved by increasing geometric surface area (GSA) and reducing bulk density (BD), namely heat capacity, using high cell-density / thinwall advanced ceramic substrates. The advanced substrates, such as 3 mil/600 cpsi and 2 mil/900 cpsi have improved the catalytic performance over the conventional substrates, and are expected to help in complying with future emission regulations, as well as catalyst downsizing. This paper describes the effects of GSA and BD using Pd-based catalysts. The reduction of hydrocarbons emissions was demonstrated significantly 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 a high temperature manifold converter with a thin wall ceramic substrate, such as; 4mil/400cpsi and 4mil/600cpsi. Double-wall cone insulation design was proposed for close-coupled converters to protect the conventional intumescent mat from high temperature. However, the double wall cone insulation is not applicable when the converter is directly mounted to the exhaust manifold without an inlet cone. The prototype manifold converter was tested under hot vibration test with a non-intumescent ceramic fiber mat and retainer rings as a supplemental support. The converter demonstrated durability for 10 hours under 80G acceleration and 100 hours under 60G acceleration with 1,050 °C catalyst bed temperature. The skin temperature of the heat shield was kept below 400 °C.