In the coming years non-road and locomotive diesel engine exhaust gas emissions will become regulated by EPA Tier4 legislation. The stringent emission limits of Tier 4 will require the use of aftertreatment technology currently being used in on-road applications. Based on the potentially large displacements of these engines, the aftertreatment systems will be large and expensive. The flow restriction that is added by the aftertreatment system will result in additional engine pumping work and lower fuel efficiency. The high durability requirements that are demanded of the aftertreatment systems is another factor that needs to be considered. Technologies that reduce complexity, size and cost of the aftertreatment system and minimize incremental fuel consumption are needed. Metal substrate technology offers a number of solutions for the challenges in meeting Tier 4 legislation. The substrates can be used for oxidation catalysts, selective catalytic reduction and slip catalysts depending on what kind of coating is applied to them. The thin wall technology that metal substrates can offer, even at coarse cell densities and lack of required retention mat for system integration provides more open frontal area, leading to lower flow restriction and lower fuel consumption. When designing a modular exhaust system, the shape flexibility will allow for denser packaging of the catalysts. This maximizes the amount of available cross-sectional area, leading to a most compact exhaust system and again better fuel efficiency. Large diameter catalysts can be manufactured in one piece, rather than being joined together from several pieces. A more robust substrate is the outcome.

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