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In August of 2011, the US Environmental Protection Agency issued new Green House Gas (GHG) emissions regulations for heavy duty vehicles. These regulations included new procedures for the evaluation of hybrid powertrains and vehicles. One of the hybrid options allows for the evaluation of an engine plus a hybrid transmission (a powertrain). For this type of testing, EPA has proposed simulating a vehicle following the hybrid vehicle test procedures, including the use of the vehicle cycles and the A to B comparison testing - as required for the full vehicle evaluation option. This paper proposes an alternative approach by defining a powertrain cycle. The powertrain cycle is based on the heavy duty engine emissions cycle - the transient FTP cycle. Simulation and test results are presented showing similar performance over the engine and vehicle cycles. This approach offers several advantages as compared to the procedure described in EPA's GHG rule.

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.