Nonroad Engine Activity Analysis and Transient Cycle Generation

The United States Environmental Protection Agency (EPA) has initiated Phase I of a regulatory program to control exhaust emissions of nonroad diesel engines over 37 kW. Central to any emissions regulation is the test procedure, which must include an appropriate test cycle. Based on actual in-use speed and estimated torque data collected from an agricultural tractor, a backhoe-loader, and a crawler tractor, three duty cycles were developed. Using an iterative process, comparison of chi-square statistical data was used to identify representative microtrips, segments of engine operation gathered during performance of selected activities. Representative microtrips for specific activities for a particular nonroad application were “strung” together to make up a test cycle. Before accepting the test cycle, data for the cycle was compared to statistical data used to characterize the raw data in an effort to validate that the cycle was representative of the raw data. After validating the transient cycle, it was transformed into a schedule of torque and speed points at one-second intervals, to facilitate engine testing. Using a reference speed, referred to as Governor Central Speed, the cycle speed points were normalized. The torque points were normalized using the transient federal test procedure (FTP). A representative transient test cycle for each of the agricultural tractor, the backhoe-loader, and crawler tractor developed from this work have been used to conduct emissions tests on diesel engines, and these cycles are referenced here to provide a means to perform a laboratory assessment of nonroad engine emissions.