Light-Duty Diesel Emission Correction Factors for Ambient Conditions

To determine the effects of ambient conditions on emissions from light-duty diesels, 174 emission tests were conducted on four vehicles. The major program objective was estimation of a factor to correct NO_x emissions to a standard humidity. Other emissions and ambient conditions were also examined for relationships by regression analysis.

Humidity effects on NO_x emissions were found to be substantial and quite predictable. Relationships observed between other emissions and ambient conditions were relatively weak and unpredictable. Several types of NO_x-humidity correction factors were estimated and compared to those already used for other vehicle and engine classes.