Conventional (Otto cycle) natural gas engines are limited in power and thermal efficiency relative to a diesel engine due to detonation and the need to run a nearly stoichiometric air/fuel ratio. Technology is under development to burn natural gas in a direct-injected diesel cycle that is not prone to detonation or air/fuel ratio control limitations. Direct-injected gas (DIG) technology will allow natural gas engines to match the power and thermal efficiency of the equivalent diesel-fueled engine. Laboratory development now under way is targeted for field experimental evaluation of a DIG 3516 engine in a 1500 kW road switcher locomotive. This paper will describe DIG 3516 engine component design and single and multicylinder performance development.

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