Distribution of Warm-Up and Underfloor Catalyst Volumes

In an effort to reduce hydrocarbon emissions for the upcoming vehicle emission regulations, FTP emissions were measured after the warm-up and underfloor converters using a four cylinder 2.3L 1991 engine on an auto-driver dynamometer stand. The warm-up and underfloor converter were located approximately 13 and 69 cm. respectively from the exhaust manifold. The warm-up and underfloor converter volumes varied from 0 - 2.67 liters. A total catalyst volume of 2.67 liters was distributed in 0.67 liter increments between the warm-up and underfloor converters. All of the converters were dynamometer aged appropriately with respect to their intended position in the exhaust system. Platinum/rhodium catalysts were evaluated in the underfloor location with platinum/rhodium or palladium containing catalysts in the warm-up location. The results indicated that: 1) The warm-up converters were effective at reducing Phase 1 and 3 hydrocarbon emissions. 2) The palladium containing warm-up converters performed better than the platinum/rhodium warm-up converters. 3) The underfloor converters were not active during Cycle 1. 4) The catalyst volume of the palladium warm-up converters should be near 0.67 liters or greater.