Off-highway transient driving cycle

Southwest Research Institute and the EPA teamed to determine the necessary emissions tests and certification cycles for off-highway engines.

The U.S. Environmental Protection Agency (EPA) and Southwest Research Institute have begun the initial phase of a new regulatory program to control exhaust emissions of off-highway diesel engines of more than 37 kW (50 hp). Central to any emissions regulation is the test procedure, which must include an appropriate test cycle. A preliminary examination of engine operation in heavy-duty off-highway equipment was undertaken to determine whether emissions from such equipment could be adequately assessed by testing over selected steady-state operating modes, or whether transient test operations were more appropriate.

Speed and torque data describing how engines operate in off-highway equipment was almost nonexistent. Three pieces of diesel-powered, off-highway equipment - a crawler tractor, a backhoe-loader, and an agricultural tractor - were used to generate a limited database.