Six 2001 International Class 6 trucks participated in a project to determine the impact of gas-to-liquid (GTL) fuel and catalyzed diesel particle filters (DPFs) on emissions and operations from December 2003 through August 2004. The vehicles operated in Southern California and were nominally identical. Three vehicles operated “as-is” on California Air Resources Board (CARB) specification diesel fuel and no emission control devices. Three vehicles were retrofit with Johnson Matthey CCRT® (Catalyzed Continuously Regenerating Technology) filters and fueled with Shell GTL Fuel.
Two rounds of emissions tests were conducted on a chassis dynamometer over the City Suburban Heavy Vehicle Route (CSHVR) and the New York City Bus (NYCB) cycle. The CARB-fueled vehicles served as the baseline, while the GTL-fueled vehicles were tested with and without the CCRT filters. Results from the first round of testing have been reported previously (see 2004-01-2959).
The second round results were compared to the CARB specification diesel fuel baseline. Over the CSHVR cycle, the GTL Fuel (no filter) reduced oxides of nitrogen (NOx), hydrocarbon (HC), and particulate matter (PM) emissions by 13%, 46%, and 21%, respectively, and increased carbon monoxide (CO) by 11%. The GTL Fuel and the CCRT filter virtually eliminated the HC, CO, and PM emissions and reduced NOx emissions by 22%, a statistically significant reduction.
Testing over the NYCB cycle also revealed emission reductions are possible with GTL Fuel. Compared to the CARB specification diesel fuel, the GTL Fuel provided statistically significant reductions in NOx, HC, and PM emissions by 11%, 58%, and 16%, respectively. A 10% increase in CO emissions was also noted, although not statistically significant. With the CCRT filter, the HC, CO, and PM emissions were reduced by over 95%. A statistically significant NOx reduction of 20% was observed.
Reductions from round 2 were notably larger than those in round 1. To determine if the changes observed between rounds were “real”, a statistical analysis was performed. The analysis found that CO emissions were higher without the filter in round 2, while no changes were observed for HC or PM emissions. The NOx emissions were significantly higher in round 1 for the NYCB cycle only.
The fleet was followed for operability for 6 months and accumulated ∼20,000 miles. Driver feedback for the vehicles operating on the GTL Fuel and CCRT filters was very positive. An analysis determined that the fuel economy with the combination of GTL Fuel and CCRT filters decreased by 8%. Evaluation of the maintenance records did not reveal any impact of the GTL fuel or CCRT filters on operability.