THE COMPOSITION OF MOTOR-VEHICLE ORGANIC EMISSIONS UNDER ELEVATED-TEMPERATURE SUMMER DRIVING CONDITIONS (75 TO 105-DEGREES-F) .2.

Emissions from nine popular late-model motor vehicles with four-cylinder engines were characterized at three test temperatures to simulate summer driving. Six vehicles were fueled by throttle body injection (TB) and three by port fuel injection (PFI). The vehicles were tested at temperatures of 75, 90 and 105-degrees-F with unleaded regular summer grade fuel. Tailpipe and evaporative emissions were determined at each test temperature. The emissions measured were total hydrocarbons (THCs), speciated hydrocarbons (200+ compounds and isomers), speciated aldehydes, carbon monoxide (CO), oxides of nitrogen (NOx), benzene and 1,3-butadiene. Tailpipe emissions of THC from the TBI were relatively stable, but THC emissions from the PFI vehicles decreased slightly as test temperature increased. CO emissions from the TBI vehicles increased and those from the PFI vehicles decreased as test temperature increased. NOx emissions from both TBI and PFI vehicles increased with increased test temperature. Benzene and 1,3-butadiene emissions from the TBI vehicles showed no temperature sensitivity, but emissions from the PFI vehicles decreased with test temperature increases. Formaldehyde, acetaldehyde and total aldehydes in general showed no temperature sensitivity. Evaporative (diurnal and hot soak) emissions from both TBI and PFI vehicles generally increased with test temperature increase. Evaporative emissions from the TBI vehicles were greater than those from the PFI vehicles. The first paper of this two-part series was published in the February 1992 issue of the Journal of the Air & Waste Management Association.