Dual Fuel Engine as the name suggests runs on two fuels i.e. diesel and CNG. The air and CNG is mixed in a pre-mixer and injected into the inlet manifold during the suction stroke. Before the piston reaches from BDC to TDC, pilot fuel (diesel) is injected in the cylinder which auto-ignites due to high pressure and temperature inside the cylinder and burns the mixture of air-CNG and combustion occurs. The dual fuel operation does not involve any major engine modification, only a pre-mixer is attached on the inlet manifold. In dual fuel engines, at low loads when the gaseous fuel concentration is low, ignition delay period of the pilot fuel increases and some of the homogeneously dispersed gaseous fuel remains unburned and results in poor performance. A concentrated ignition source is needed for the combustion of the induced fuel at low loads. Further the injection timing of the pilot fuel, injector opening pressure, pilot fuel quantity and intake temperature are some of the important variables controlling the performance of dual fuel engines at high loads. This process has the advantage of instant switchover to diesel-only operation, in case natural gas is unavailable. The degree of diesel replacement by natural gas depends on - the engine operating conditions and the engine design to some extent, typically varying from 60% to 70%. The dual fuel technology has been much more successfully used in engines with less variation of load, where the engine speed varies in a small range. The use of diesel fuel allows the retention of the diesel compression ratio and its efficiency while the natural gas contributes to economy and is responsible for lower and eco-friendly emissions.

Advantages of dual fuel engine:
1. Lower emissions and less harmful pollutants in the exhaust gas which helps to reduce the percentage of green house gases and prevents global warming to some extent.
2. Power produced by the engine remains same during dual fuel mode.
3. Switchover from dual fuel mode to diesel mode is very simple and can be operated by a switch.
4. The kit can be attached to the diesel engine currently fitted in the three wheelers,pumps,generators etc. without any modification in the engine.
5. There are no sensors in the kit and it is fully manual so the cost of kit is also less approx. ? 15000.