A Work-Based Window Method for Calculating In-Use Brake-Specific NOx Emissions of Heavy-Duty Diesel Engines 2008-01-1301

A work-based window method has been developed to calculate in-use brake-specific oxides of nitrogen (NOx) emissions for all engine speeds and engine loads. During an in-use test, engine speed and engine torque are read from the engine's electronic control unit, and along with time, are used to determine instantaneous engine power. Instantaneous work is calculated using this power and the time differential in the data collection. Work is then summed until the target amount of work is accumulated. The emissions levels are then calculated for that window of work. It was determined that a work window equal to the theoretical Federal Test Procedure (FTP) cycle work best provides a means of comparison to the FTP certification standard. Also, a failure criterion has been established based on the average amount of power generated in the work window and the amount of time required to achieve the target work window to determine if a particular work window is valid.

Data collected during Phase IV of West Virginia University's in-use testing program were used to show that the work window method produces in-use brake-specific NOx values similar to the 30 second Not-To-Exceed (NTE) window method, which was applicable at the time of testing, and the continuous NTE window method over different highway and urban test routes for a variety of engine configurations.