A system, method and apparatus for controlling a gas substitution characteristic in a dual fuel engine are provided. The gas substitution characteristic can be controlled based on measured characteristics directly or indirectly associated with operation of the dual fuel engine, including intake manifold air pressure (IMAP), load of the dual fuel engine, ambient air temperature, exhaust temperature, fan speed, and/or pressure of natural gas supplied to the dual fuel engine. Further, the gas substitution characteristic can be controlled by controlling intake manifold air temperature (IMAT) based on control of a cooling capacity of a cooling circuit.

Methods of operation of liquid and gaseous multi-fuel compression ignition engines that may be operated on a gaseous fuel or a liquid fuel, or a combination of both a gaseous fuel and a liquid fuel at the same time and in some embodiments, in the same combustion event. Various embodiments are disclosed.

The present invention provides a novel combination of devices to measure and transmit to an electronic controller data pertaining to differential pressures, temperatures, regeneration status, exhaust content, accumulated gas consumption and substitute fuel consumption. The electronic controller compares the data to thresholds; when the controller receives signals indicating these thresholds or limits are met, the controller causes the gas substitution rate to be diminished or set to zero until after-treatments elements are fully regenerated thereby facilitating integration of a mixed fuel system with an application internal combustion engine.