CLASS 8 TRUCK EMISSIONS TESTING: EFFECTS OF TEST CYCLES AND DATA ON BIODIESEL OPERATION

Abstract

Design of cycles for chassis emissions testing of heavy duty trucks is in its infancy, and no cycle trulyrepresentative of in-use behavior of trucks with manual transmissions is currently available. Class 8 tractors were testedfor emissions using two Transportable Heavy Duty chassis dynamometer systems. The vehicles were tested on diesel andbiodiesel using the West Virginia University WVU 5 peak cycle, which has prescribed accelerations, cruise sections, anddecelerations and covers a 5 mile (8 km) distance. Also, a test cycle that was similar, but employed maximum accelerationrates under the control of the driver was used: this was termed the WVU 5 mile route. Emissions of carbon monoxide(CO) and particulate matter (PM) were substantially higher for the WVU 5 mile route than for the WVU 5 peak cycle,which can be explained in terms of air:fuel ratio. Emissions of hydrocarbons (HC) and oxides of nitrogen (NOx) were lessaffected. The WVU 5 mile route may be favored in the future in that it examines full load emissions. To compare emissionsbetween vehicles fueled with No. 2 diesel (D2) and a blend of 65% D2 with 35% soy biodiesel (BD35), eight class 8tractors were operated through the WVU 5 peak cycle. Emissions of CO, HC and PM were lower on average for theBD35 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 slightlyhigher on average for all three-engine types with the BD35. Differences in many cases were small, as were sample sizes,so that additional data is desirable before reaching definitive conclusions.