Use of the West Virginia University Truck Test Cycle to Evaluate Emissions from Class 8 Trucks

Emissions from light duty vehicles have traditionally been measured using a chassis dynamometer, while heavy duty testing has been based on engine dynamometers. However, the need for in-use vehicle emissions data has led to the development of two transportable heavy duty chassis dynamometers capable of testing buses and heavy trucks. A test cycle has been developed for Class 8 trucks, which typically have unsyncronized transmissions. This test cycle has five peaks, each consisting of an acceleration, cruise period, and deceleration, with speeds and acceleration requirements that can be met by virtually all vehicles in common service. Termed the “WVU 5 peak truck test”, this 8 km (5 mile) cycle has been used to evaluate the emissions from diesel and ethanol powered over-the-road tractors and from diesel and ethanol powered snow plows, all with Detroit Diesel 6V92 engines. In addition, emissions data from a Cummins powered diesel tractor were obtained for operation with and without an engine brake. The new WVU 5 peak truck test cycle was readily followed by all trucks tested, with small speed deviations and close to the desired total distance traveled. Tests show that these trucks could not follow the Central Business District cycle, usually used for buses. Data in g/km (g/mile) were obtained for emissions of carbon monoxide, oxides of nitrogen, hydrocarbons and particulate matter. As an example of the data acquired, it was found that particulate matter emissions were lower for an ethanol powered tractor in comparison to an otherwise identical diesel tractor. For the same vehicles, carbon monoxide emissions were lower for diesel fueled vehicles, while oxides of nitrogen were lower for ethanol fueled vehicles.