Effect of Cold Weather on Motor Vehicle Emissions and Fuel Consumption - II

The effect of soaking temperature on exhaust emissions and fuel consumption was investigated using a variety of automobiles representing different emission control levels including diesel engine powered vehicles. Tests were performed at soaking and ambient temperatures of 20°C down to -20°C (68°F to -4°F).

It was found that emissions and fuel consumption are dependent on soaking temperature. Hydrocarbon and carbon monoxide emissions were higher at -20°C than at 20°C: hydrocarbon (HC), 1 to 4 times; carbon monoxide (CO), 1 over 3 times. The smallest increase of 1 to 1.04 time belonged to vehicles equipped with diesel engines. Nitrogen oxides (NO_x) emissions were higher or lower at -20°C than at 20°C depending on emission control technologies -0.75 to 1.11 times. Analysis of the data has indicated that HC and CO emissions from the cold start phase of the Federal test were the most sensitive to soaking temperature. With NO_x emissions the soaking temperature sensitivity was fairly constant throughout the three phases of the test.

It appears that temperature sensitivity of fuel consumption in vehicles equippped with diesel engines and lean burn gasoline engines is considerably lower in comparison to the vehicles equipped with other control technologies, and is higher at -20°C than at 20°C: for diesel engines and lean burn -1.15 times; for other vehicles -1.55 times. The data also indicate that the temperature sensitivity of fuel consumption is a function of inertia weight.