1996-02-01

Impact of Revised FTP on Emissions and New Modifications Required for Catalysts 960793

New requirements for catalyst resulting from changes in FTP modes are discussed in this study.
Air conditioner(AC) operation results in dramatic changes in both engine-out and tailpipe emissions, especially NOx emission. Even though NOx emission limits will be loosened by 15% in the proposed regulations, the effect of AC operation is much greater than that. Prolonging the intermediate soak time would result in lower catalyst bed temperatures for both the close-coupled and underfloor positions. This results in a delay in light-off by 15 to 35 seconds. Tightening the A/F control under aggressive driving results in an increase in catalyst bed temperature of approximately 150°C. Also, CO and NOx emission breakthroughs are found in high space velocity(SV) operation.
Addressing this situation requires improvements in catalyst performance: 1)increase in activity, 2)lower light-off, 3)higher thermal stability and 4)increase in reactivity under extreme A/F and flow rate conditions.
Among catalysts with advanced washcoat technologies, Pd-based catalyst systems such as Pd-only and trimetal formulations help to meet these requirements.

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