NGVs are for the most part the same as gasoline cars. There are a few differences though. CNG - Compressed Natural Gas has a similar energy content to gasoline, so with some modification it can be a substitute.

Here is a step by step picture guide through how a natural gas vehicle works.

http://aftermarketcng.com/how-ngvs-work

Step 1. Compressed NG is put into the vehicle. Either from a high pressure system (like a petrol station) or a slow fill system (like in your garage). Valves are usually located in the trunk or under the hood for aftermarket work, or right in the regular gas hole for production vehicles.

Step 2: NG flows into the storage cylinders where it remains until used. Tanks are usually located in the front of the boot.

Step 3: CNG leaves the storage tanks and goes through a manual shutoff valve. The shutoff is required in all converted vehicles.

Step 4: CNG flows from the shutoff valve into the engine compartment. The CNG flows into the regulator which lowers the pressure of the natural gas.

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