Exhaust emissions from motor vehicles in low ambient temperature conditions

This paper presents cold–start emissions results for cars representing typical present–day emission control technology for the former European ERA countries (i.e. Sweden, Finland, Norway, Austria and Switzerland). For most of the cars, this means a three–way catalytic converter with closed–loop air–fuel ratio control and multi–point fuel injection system. The ambient temperature during the test was 0°C, and the first phase (505 seconds) of the FTP75 driving cycle was used to assess the performance. Our test results indicate, that, even if any TWC vehicle with state–of–the–art technology has quite low emissions levels, when its performance is evaluated using the standardized certification and type approval procedures, it produces substantially higher emissions levels, especially carbon monoxide and unburned hydrocarbons when the ambient temperature falls below the temperature range determined in the emission regulations. The technology available to lower the adverse effects of cold–starts to emissions is also discussed.