Emissions Certification Vehicle Cycles Based on Heavy Duty Engine Test Cycles

This paper describes the development vehicle cycles based on heavy duty engine test cycles for emissions certification. In the commercial vehicle and industrial equipment markets, emissions are evaluated using engine test cycles. For the on-highway market in the United States, these cycles include the transient heavy duty engine FTP test, and the steady state heavy duty engine SET test. Evaluation of engine only emissions is a practical approach given the diversity of applications, small volumes, and lack of vertical integration in the commercial vehicle market. However certain vehicle and powertrain characteristics can contribute significantly to fuel consumption and emissions. A number of approaches have been proposed to evaluate vehicle performance, and all of these vehicle evaluation methodologies require the selection of a vehicle cycle. If the engine test cycles and vehicle test cycles are not aligned, a technology evaluation will give different results depending on whether an engine test or vehicle test is used. With future regulations potentially allowing engine or vehicle test options, the alignment of the vehicle and engine test cycles is especially important.

In this work, a vehicle FTP cycle and a vehicle SET cycle were created based on the transient engine FTP and engine SET tests. The vehicle cycles are the same duration and have similar power requirements to the engine cycles. Simulation and test results are presented showing similar performance over the engine and vehicle cycles. Alignment of vehicle test cycles with the engine FTP and engine SET cycles will maintain consistency of vehicle and engine emissions evaluations, and will provide a link between future vehicle evaluations and existing experience with engine emissions testing.