The 1298 cc four-cylinder, four-stroke spark ignition engine was modified for CNG direct injection through adjustments to the cylinder head. A key challenge in this conversion was the placement of the CNG injector relative to the spark plug, as the original head design was optimized for petrol operation and lacked the necessary compartments. To cater to both aspects of the setup adjustments were made to the cylinder head which resulted in a compression ratio. The research adopted a technique by introducing CNG into the combustion chamber while the compression stroke was ongoing, similar, to how diesel engines function. This process entailed creating openings on the cylinder head near the exhaust valve side, for CNG infusion. Brass connectors were affixed in these apertures linking them to high-pressure CNG injectors located outside the cylinder head through steel tubing coated with rubber. The high-pressure CNG was delivered to the injector rail through a two-stage pressure reducer system, in place. The gas operation was overseen by a customized CNG engine control module and specialized software. The conversion process involved installing components like a CNG tank, injector emulator timing advance processor (TAP) and sensors. The performance of the engine was tested using both CNG-SI and CNG-DI systems across speeds ranging from 1000 to 3100 rpm. The results showed that the CNG-DI system managed to reduce fuel consumption by 3–10% and improve brake efficiency by 1–2%. Moreover it demonstrated a 4–6% increase, in volumetric efficiency and a leaner air fuel ratio when compared to the CNG-SI system.