In a recent paper, Opposed-Piston 2-Stroke Multi-Cylinder Engine Dynamometer Demonstration  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.In this second paper, the OP engine transient capabilities were assessed by testing the engine performance and emissions response under a typical transient maneuver: 25% to 100% load step at low and constant engine speed. It can be seen that during such transition, it is possible to control both NOx and Soot with a minimal torque lag.Additionally, this paper will present the ability of the OP engine to manage exhaust temperatures. It is shown that the air system control flexibility and robust combustion system that Achates Power developed for the OP engine can be used to achieve high exhaust gas temperatures for a diesel engine at idle-like speeds and loads. In this initial exercise, it is shown that close to 500°C engine out temperature can be achieved at 1100RPM with no torque output.