Regulated and Unregulated Emissions from Catalyst Vehicles at Low Ambient Temperatures

Cold operating environment has many kinds of negative effects on the use of automobiles. Low ambient temperature degrades start-up performance and increases fuel consumption. Hence, the amounts of exhaust emissions are also elevated. In particular, high concentrations of CO and HC are present in the exhaust. Cold-start derates especially the performance of a TWC type of emission reduction. Therefore, an increasing emphasis has been set to the testing of exhaust emissions even at sub-ambient temperatures, For this reason, US-EPA has recently revised US emission regulations by comprising an additional low ambient temperature (20°F = -7°C) test for CO emissions.

Apart from the regulated components, other poisonous compounds have been detected from the exhausts, although usually in very small quantities, A cold-start may have an increasingly strong effect even to the emission of these substances. Therefore, as many as possible of these compounds should be included into the low temeperature emissions analysis. Current methods for detecting these components are primarily based on ‘wet chemistry’. Therefore, they are very laborous and allow no real-time analysis of transient phenomena. However, recent R&D efforts have made fast FTIR-technology available also to the engine exhaust analysis applications. The paper lists some preliminary results for this type of work.