Class 8 truck emissions testing: Effects of test cycles and data on biodiesel operation

Design of cycles for chassis emissions testing of heavy duty trucks is in i ts infancy, and no cycle truly representative of in-use behavior of trucks with manual transmissions is currently available. Class 8 tractors were tes ted for emissions using two Transportable Heavy Duty chassis dynamometer sy stems. The vehicles were tested on diesel and biodiesel using the West Virg inia University WVU 5 peak cycle, which has prescribed accelerations, cruis e sections, and decelerations and covers a 5 mile (8 km) distance. Also, a test cycle that was similar but employed maximum acceleration rates under t he control of the driver was used: this was termed the "WVU 5 mile route". Emissions of carbon monoxide (CO) and particulate matter (PM) were substant ially higher for the WVU 5 mile route than for the WVU 5 peak cycle, which cart be explained in terms of air:fuel ratio. Emissions of hydrocarbons (HC ) and oxides of nitrogen (NOx) were less affected The WVU 5 mile route may be favored in the future in that it examines full load emissions. To compar e emissions between vehicles fueled with No. 2 diesel (D2) and a blend of 6 5% D2 with 35% soy biodiesel (BD35), eight class 8 tractors were operated t hrough the WW 5 peak cycle. Emissions of CO, HC and PM were lower on averag e for the BD35 when used in newer Detroit Diesel Series 60 350 hp (261 kW) engines and 1989 Cummins 855 in.(3) (14 L) 315 hp (235 kW) engines, but for 1989 Mack E-6 350 hp (261 kW) engines, only CO was lower Emissions of NOx were slightly higher on average for all three-engine types with the BD35. D ifferences in many cases were small, as were sample sizes, so that addition al data is desirable before reaching definitive conclusions.