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After having tested basic transient maneuvers such as load-step changes on the 4.9L three-cylinder opposed-piston diesel engine [1], a similar test-engine was subjected to a more aggressive test-routine - a hot-start heavy-duty FTP (Federal Test Procedure) transient cycle for the on-road engines. The three main objectives of this exercise were: 1 To assess the ability of the engine to meet the transient cycle requirements while maintaining close to the cycle-average BSFC for the FTP cycle derived from steady-state torque-to-fuel map. 2 To attain engine-out brake-specific emission levels that are compatible with US2010 EPA requirements with a conventional after-treatment system consisting of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF) and a selective catalyst reduction (SCR) system. 3 To compare hot-start FTP transient cycle fuel economy with a publicly available benchmark.

In a recent paper, Opposed-Piston 2-Stroke Multi-Cylinder Engine Dynamometer Demonstration [1] published at the SAE SIAT in India in January 2015, Achates Power presented work related to the first ever opposed piston multi-cylinder engine fuel economy demonstration while meeting US 2010 emissions. The results showed that the research 4.9L three cylinder engine was able to achieve 43% brake thermal efficiency at the best point and almost 42% on average over the 12 modes of the SET cycle. The results from this test confirmed the modelling predictions and carved a very robust path to a 48% best BTE and 46.6% average over the cycle for a production design of this engine. With the steady state performance and emissions results achieved, it was time to explore other attributes.