A Warm-Up - Underfloor Converter Parametric Study: Effects of Catalyst Technology on Emission Performance

A parametric study was performed to investigate the interactions between Pd warm-up and underfloor converters on FTP emissions. Three different Pd warm-up converters were evaluated with six different underfloor converters on two different engines. The Pd warm-up converters primarily differed in the amount of ceria in the catalyst washcoat. These warm-up converters had a catalyst of 0.52 liters and a Pd loading of 100 g/ft3. The underfloor converters had a catalyst volume of 2.67 liters. Two Pt/Rh and one Pd catalyst technology were used in the underfloor converters. Each underfloor catalyst technology was investigated at two different loadings. The Pt/Rh underfloor converters were evaluated at 25 and 50 g/ft3 at a Pt/Rh ratio of 14/1. The Pd containing underfloor converters were evaluated at 50 and 100 g/ft³. All of the converters used in this study were dynamometer aged appropriately with respect to their intended position in the exhaust system. FTP emissions were measured using a four cylinder 2.3L and six cylinder 3.8L engine on an auto-driver FTP dynamometer stand. The FTP results indicate that improvements in HC emissions can be achieved using Pd containing catalysts and that the activity of a warm-up converter can impact tailpipe emissions depending on engine calibration and/or exhaust system configuration.