A Warm-up and Underfloor Converter Parametric Study

Parametric studies were performed to determine the effects and interactions between aged warm-up and underfloor converters with respect to 1) catalyst volume, 2) precious metal loading and 3) catalyst technology. All the converters were dynamometer aged appropriately with respect to their intended position in the exhaust system prior to emission testing. FTP emissions were measured using a 2.3L engine on an auto-driver dynamometer stand. Catalyst volumes of the warm-up and underfloor converters varied from 0.00 to 1.03 and 1.34 to 2.67 liters, respectively. Precious metal loading of the warm-up converters varied from 50 to 300 g/ft3 of palladium (Pd). The underfloor converters used both platinum/rhodium (Pt/Rh) and Pd precious metal combinations. Pt/Rh loadings varied from 25 to 50 g/ft3 at a 14/1 ratio. Pd loadings varied from 50 to 100 g/ft3. The underfloor catalyst technologies varied in base metal content and/or high temperature stabilizers. The Pd warm-up catalyst technology is a high temperature stabilized ceria containing washcoat. The FTP results indicate significant reduction in HC emissions can be achieved with a Pd containing warm-up converter. However, CO tailpipe emissions increased when a more active warm-up converter was used with the large underfloor converters.