Among the challenges in the internal combustion - spark ignition Gasoline Direct Injection (GDI) engines stayed under spotlight for its ability to be developed in terms of fuel conversion efficiency and emission contaminants. Spray analysis is of great importance for the combustion operation and it is a prerequisite for improving the mixing capabilities of the air/fuel mixture. Momentum flux measurement technique is one of the most interesting approaches that aims to study the spray structure which can be a complement for high-speed imaging and Phase Doppler Anemometry (PDA) analysis. In the present study, two GDI single-hole research injectors, Magneti Marelli with Length to Diameter parameter (L/D)=1; 3 are investigated by means of momentum flux, global and local, under both low and high temperatures. The flash-boiling phenomenon is triggered when static pressure is below fuel saturation pressure at the same temperature which drastically affects the spray structure in terms of decrement in the penetration rate accompanied with an enlargement in the cone angle. N-heptane is used as a fuel under a temperature range 30..