Based on this research, trend in fuel – air mixing with injection timing of 77.5 degrees BBDC, the injector with two holes was better for fuel-air mixing. The improved spray flow was spread more evenly in the combustion chamber and the CNG fuel could flow into the combustion chamber as a rich mixture with intake air. In the fuel flow velocity profile of the new two, tree, four and five-holed nozzle injectors, the fuel flow velocity of 4 holes is better for injection timing at 77.5, 63.6, 43.7 and 26.9 degrees BBDC compare to the others new multi holes injector nozzle.