Optimization of an emissions-certified dual fuel delivery truck

Urban air quality concerns are producing strong pressure to reduce diesel engine emissions. One option is to convert to a dual fuel diesel/natural gas system, taking advantage of the clean burning nature of gas. With the dual fuel conversion, natural gas metered into the intake air by a multi-point fuel injection provides most of the fuel while only small pilot injection of diesel is needed to ignite the gas. Both fuels are electronically controlled and the fully mapped system can be programed to use over 85% natural gas. To minimize tailpipe emissions, electronically-controlled exhaust gas recirculation (EGR) and an oxidation catalyst can be used. Such a dual fuel system has been developed for the Japanese Isuzu ELF 250 2-ton truck. A converted truck has been operating in Japan and tested periodically to demonstrate practicality, durability and continued emission reductions. The truck operates normally but runs quieter and with substantially reduced emissions. This paper presents development results and the techniques and tradeoffs used to achieve results.