The gas tank is kept somewhere around the boot and connected with gas hose that runs parallel with the fuel line down to the injector. From here the hose will be fed into the adapter that is already designed to accomodate both the petrol and CNG injectors at same time. New CNG ECU will be installed and powered with the new wiring harness.
Reason for installing another ECU is because CNG uses a different Air : Fuel mixture unlike petrol that use 16.5 : 1, so the two ECU will now be working hand in hand but the driver decides which one to use just by pressing a switch that will be mounted on the dashboard to select running on gas or petrol.
NOTE: The CNG gas tank comes with a control box that have fuel guage, pressure release valve, solenoid valve, regulator etc so you always monitor your gas level.
FOR THE CONSUMPTION
* 1kg of CNG covers about 32.5 km on highway.
* 1 liter of petrol covers about 21.8 km on highway.
If you're asking if this works, one Oil & Gas company in lagos that deal mainly on Aviation fuel have been powering their fleet of Honda Civic they use as official cars with CNG for decades now but your not aware of this.
During my research, I found out that in Kenya i discovered that's what most of their taxi use and its serving them well but it's unfortunate i don't have interest on it then, maybe the federal government of Nigeria need to go back to Kenya to do more study on the construction and installation.