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

Emissions from seven late-model popular V-6 and V-8 motor vehicles were characterized at three test temperatures. The Urban Dynamometer Driving Schedule was used for vehicle tailpipe testing. Six vehicles fueled by port fuel injection (PFI) and one vehicle with a carbureted fuel system were tested at temperatures of 75, 90, and 105-degrees-F with unleaded regular summer grade gasoline. Tailpipe and evaporative emissions were determined at each test temperature. Measured emissions were the total hydrocarbons (THCS), speciated hydrocarbons, speciated aldehydes, carbon monoxide (CO), oxides of nitrogen (NOx), benzene, and 1,3-butadiene. In general, tailpipe emissions of THC, benzene, and 1,3-butadiene from the vehicles were not temperature sensitive, but the CO and NOx emissions showed some temperature sensitivity. Formaldehyde, acetaldehyde, and total aldehyde emissions from the PFI vehicles were also not temperature dependent, while formaldehyde emissions from the carbureted vehicle decreased slightly with increasing test temperature. Evaporative THC emissions generally increased with increasing test temperature. Hydrocarbon emissions saturated and broke through the evaporative carbon canister of one PFI vehicle during the 105-degrees-F hot soak while the other six vehicles showed no hydrocarbon breakthrough.