A governing strategy for dual fuel engines retrofitted from diesel engines was developed based on fuel equivalent. The strategy adopted two closed loops to control the switching of two fuels

and it was tested on a dual fuel engine retrofitted from an X6170 marine diesel engine. The test results show that without changing the main structure of the base engine

the developed strategy enables the retrofitted diesel-gas dual fuel engine to replace the original one with lower fuel consumption and lower emissions

and with a smooth switching of two fuels. But HC emission and the exhaust temperature are much impacted when the gas content is too high.