Emissions Correlation of Heavy-Duty Transient Test Facilities

A correlation program was established between heavy-duty engine transient test facilities in order to determine emission variabilities within and among laboratories. Significant differences between the laboratories observed for all emission components were smaller compared to data reported previously. For gaseous emissions among-lab standard deviation was significantly, for particulates only slightly higher than within-lab standard deviation. Two groups of laboratories were found that correlate rather well within the respective group.

Normalizing the standard deviations to 1991 emission regulations showed that oxides of nitrogen and hydrocarbon variabilities were about 16 %, particulate variability about 45 % of the regulated emission values. Therefore, particulate measurement has to be improved considerably.

Cycle work was found to influence among-lab variability of all components. Besides, sample zone temperature affected the absolute particulate, and dilution ratio the absolute hydrocarbon emissions. Amendments to the test procedure are recommended to improve measurement accuracy.