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Growing world vehicle populations and persistent air quality problems require further reductions in the emissions from engines. Future tailpipe emission limits mandate 98%+ reductions in hydrocarbons, 95%+ reductions in Carbon Monoxide and 95%+ reductions in Nitrogen Oxides. Further complexities are introduced by new, demanding driving norms according to which these standards are applied, as well as the on-board diagnostics to ensure in-use compliance. Customized and optimized emission control system designs will be needed for each specific engine family. The new emission control systems will incorporate integrated heat management, advanced catalyst formulations, optimized substrates and substrate packaging as well as the use of pollutant storage materials and supplemental heating devices.

The reduction of emission levels for low (LEV) and ultra low (ULEV) emissions vehicles requires catalyst with rapid thermal response for quick light-off while providing stable high temperature performance under highway driving conditions. The design of substrates which carry the three-way catalyst formulations are key to meeting the complex dual performance requirements. Enhanced mass transfer and reduced thermal mass can be accomplished while maintaining acceptable back pressure. The design principles and selection of substrate properties are described as is their effect on the emissions from the Federal Test Procedure. Transient driving performance simulations allow for selection of optimum advanced substrate designs.