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Further stringent emission legislation requires advanced technologies, such as sophisticated engine management and advanced catalyst and substrate to achieve high catalytic performance, especially during the light-off phase. This paper presents the results of calculations and measurements of hydrocarbon and carbon monoxide light-off performance for substrates of different wall thickness, cell density and cell shapes. The experimental data from catalyst light-off testing on an engine dynamometer are compared with theoretical results of computer modeling under different temperature ramps and flow rates. The reaction kinetics in the computer modeling are derived from the best fit for the performance of conventional ceramic substrate (6mil/400cpsi), by comparing the theoretical and experimental results on both HC and CO emissions. The calibrated computer model predicts the effects of different wall thickness, cell density and cell shape.

New ultra-low vehicle emission legislation requires advanced catalyst systems to achieve high conversion requirements. Manufacturers have to improve both the washcoat formulations and the catalyst substrate technology to meet these new regulations. This paper will present the results of a computer modeling study on the effects of ultra-thinwall catalysts on hydrocarbon and carbon monoxide light-off performance improvement. The experimental data from catalyst light-off testing on an engine dynamometer are compared with theoretical results of advanced substrate modeling for ultra-thin wall ceramic substrates. Results show that thermal mass has the greatest effect on light-off performance. Decreases in wall thickness offer the greatest benefit to light-off performance by lowering the thermal mass of the substrate, thus allowing it to reach light-off temperature faster.