A test program was conducted to study the effect of ambient conditions on exhaust emissions from a wide variety of automobiles. Twenty-six cars ranging from pre-control production cars to catalyst-equipped prototypes, including rotary, Diesel, and stratified charge cars, were tested at 20°, 50°, 75°, and 110° F.
Ambient temperatures above and below 75° F were found to have significant effects on exhaust emissions. The Diesel and stratified charge cars were affected less than production and catalyst-equipped cars by changes in ambient temperature.
The use of air conditioners at the 110° F test temperature led to increased emissions and fuel consumption. Hydrocarbon reactivity and aldehyde emissions were not affected by temperature and were lower from the catalyst cars at all temperatures.