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Compressed natural gas (CNG) has been widely used as alternatives to gasoline and diesel in automotive engines. It is a very promising alternative fuel due to many reasons including adaptability to those engines, low in cost, and low emission levels. Unfortunately, when converting to CNG, engines usually suffer from reduced power and limited engine speed. These are due to volumetric loss and slower flame speed. Direct injection (DI) can mitigate these problems by injecting CNG after the intake valve closes, thus increasing volumetric efficiency. In addition, the high pressure gas jet can enhance the turbulence in the cylinder which is beneficial to the mixing and burning. However, conversion to direct fuel injection (DFI) requires a costly modification to the cylinder head to accommodate the direct injector and also can involve piston crown adjustment. This paper discusses a new alternative to converting to DFI using a device called Spark Plug Fuel Injector (SPFI).