Exhaust emissions in cold ambient conditions: considerations for a European test procedure

Motor vehicles are seldom used in ambient conditions like those defined in current emission regulations. For example, most of the year average temperatures across Europe fall much below the range of legislative testing. Furthermore, it has been widely demonstrated that cold-starts at low ambient temperature increase the emissions. Therefore, there is a growing need to broaden the range of legislative emissions tests and set a separate low-ambient test with respective emission standards.
This paper gives emissions test results form a joint research programme between Sweden and Finland. Altogether 11 late model gasoline-fueled TWC vehicles were tested at ambient temperatures of +22 and -7 °C using a variety of different driving cycles. Apart from the driving schedule, other test parameters like vehicle preconditioning, manual vs. automatic transmission and the effect of external cooling were studied and discussed.