Multidimensional Correlation Study Using Linear Regression of PM and NOX for Heavy Duty Diesel Vehicles

When heavy-duty truck emissions rates are expressed in distance-specific units (such as g/mile), average speed and the degree of transient behavior of the vehicle activity can affect the emissions rate. Previous one-dimensional studies have shown some correlation of distance-specific emissions rates between cycles. This paper reviews emissions data sets from the 5-mode CARB Heavy Heavy-Duty Diesel Truck (HHDDT) Schedule, the Heavy Duty Urban Dynamometer Driving Schedule (UDDS) and an inspection and maintenance cycle, known as the AC5080. A heavy-duty chassis dynamometer was used for emissions characterization along with a full-scale dilution tunnel. The vehicle test weights were simulated at 56,000 lbs. Two-dimensional correlations were used to predict the emissions rate on one mode or cycle from the rates of two other modes or cycles. Oxides of Nitrogen (NO_x) and Particulate Matter (PM) emissions were the two components of emissions which were of interest, and they were reviewed in units of g/mile. The multidimensional analysis using two cycles yielded better predictive correlations for the emissions than single cycle correlations published previously. The UDDS schedule yielded the highest distance-specific emissions and it showed similar emissions as the combination of the Cruise mode and Transient mode of the HHDDT.