How to Convert a Petrol Car to CNG: Explained CNG Kit Retrofitment

Converting a petrol vehicle to run on CNG remains one of the most preferred choices among existing buyers to reduce monthly running costs by nearly 40% to 50%. However, converting modern engines requires precise technical execution, legal compliance and the right selection of components.

Retrofitment Process

To convert a petrol car to CNG involves adding a parallel fuel injection system alongside the factory-fitted petrol setup.

Engine Diagnostics

Technicians first verify engine health before modification. The person checks compression levels, spark plugs, ignition coils, and ECU health. Customers should avoid converting cars with engines having damaged piston rings or head gasket issues, as CNG burns hotter than petrol.

Cylinder Bracket & Boot Installation

Technicians will add a heavy duty steel frame directly to the chassis in the luggage compartment to mount the 12 kg CNG cylinder.

Engine Bay Hardware Fitment

The high-pressure reducer or vaporizer is placed near the engine bay firewall to drop tank gas pressure from ~200 bar to usable engine levels. The steel gas line is routed securely under the floorpan.

Manifold Tapping & Injector Rail Mounting

Sequential Systems - Intake manifold runners are fitted with brass nozzles
CNG injector rail is placed nearby to inject gas.

Wiring Harness & ECU Integration

A CNG Electronic Control Unit or ECU is wired into the car's primary harness to read signal inputs from the crank sensor, throttle position and Map sensor to control gas delivery.

Calibration & Software Tuning

A laptop is connected to the CNG ECU to calibrate injection timing maps across dynamic load bands, preventing lean-outs, misfires or check engine lights.

Sequential Vs Conventional Kits

 
Mandatory RTO Legal Process

Driving an unregistered CNG car is illegal and invalidates your vehicle insurance policy. Steps to update your vehicle's RC:

Authorised Retrofitter: the workshop will provide AIS-024/ARAI compliant kit documents
Collect installation certificate and cylinder hydro-test certificate
Submit RTO Application
Present the car at the RTO track for a physical inspection
Update RC & Insurance