Emission Systems Optimization to Meet Future European Legislation 2004-01-0138
Euro IV emissions limits have become a major milestone for the car industry in Europe. To comply with reduced emissions targets, a significant effort was required to minimize light-off time and to improve steady state performance for the pollutants HC and NOx.
The main challenges and the technical solutions are discussed in this present work. Among them are substantial catalyst improvements needed to accommodate the progressively more severe agings related to high-speed driving conditions in Europe, and the close-coupled location of the catalyst, with the introduction of the converter welded directly to the exhaust manifold.
Vehicles equipped with Euro IV emissions systems have been running in the field for more than 2 years and have shown that only a systems approach, including optimized exhaust manifold and canning designs, robust engine calibration strategies and specifically developed washcoats, can lead to a cost effective emissions solution. To meet future European emissions targets, our paper discusses the major steps that need to be taken not only to meet these targets but also to minimize cost or optimize packaging. Thus, newly developed washcoats, named Flex-Metal Catalysts, are compared to those previously used to meet Euro IV and their advantages in terms of performance and cost effectiveness are presented. The particularly severe rapid aging procedures developed to mimic the European driving style are also discussed, as well as the trade-off between converter volume and PGM content when using ultra-thin wall substrates. This trade-off has become more important in the car industry today especially for applications where only limited underhood space is available.