After having tested basic transient maneuvers such as load-step changes on the 4.9L three-cylinder opposed-piston diesel engine , 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:1To 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.2To 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.3To compare hot-start FTP transient cycle fuel economy with a publicly available benchmark.The initial results from the test are encouraging - the BSFC value is within 1.2% of the value derived from running FTP cycle on a steady-state torque-to-fuel map. The engine-out emissions (BSNOx and BSSoot) levels generated during the test are compatible with US2010 EPA tail-pipe emissions requirements and can be controlled with contemporary after-treatment systems. Furthermore, compared to the MY2011 Cummins ISB 6.7L engine, Achates Power’s OP engine presents a cycle-average BSFC advantage of 18% during hot-start FTP cycle. These results highlight the capabilities of the Achates Power OP engine to successfully run aggressive transient maneuvers without compromising the required performance attributes.