Whats the use of running dual fuels at the same time in an otto engine? both fuels have different combustion charecteristics, in your system you are probably feeding CNG to the engine with the vapor venturi - you might as well completely cut the injectors cycle and increase the gas load.
In a diesel engine - there is no air control, it only has fuel control - when you add fuel the engine accelerates, when you reduce fuel the engine decelerates. Hence when you cut down fuel you lose engine rpm or at minimum lose usable engine torque.
lets start on the very basics of IDI turbo diesel here.
when your engine is off - the injection pump goes to MAX fuel - aka start position
when you start the engine - you are greeted with a ciggie puff of black out the exhaust - but the injection pump is working off the idle settings on the metering sleeve.
when you accelerate and have no usable boost pressure (1 atm constant manifold pressure) your pump aneroid unit is keeping the metering sleeve and spring capsule at NA level to keep the engine safe and prevent overfuel smoke.
when you hit boost the aneroid moves the metering sleeve further to delay spill back and hence force more fuel volume in the injectors which when burnt with excess air from the turbo - makes more pressure in the cylinder and hence more power - carry over to more heat => more boost - the system is then cut off by either the speed governor in the pump or the wastegate on or before the turbo. - usually it happens as first the boost is cut then the speed governor kicks in.
lets remove the aneroid sense line - now what happens is that the turbo is spinning away but making neglible boost as you dont have the fuel to create heat to shove the turbine to speed - the pump does not GAS (give a chit) to add fuel because the aneroid is not pushing down the lever for the metering sleeve.
the new fangled DI engines with turbos and fuel pressures of 20~30,000 psi on the rail are no different in basic operation.
you may have a revolving engine with low fuel - but that engine will be useless if I want to make it pull a load.
