The combustion characteristics and emissions in IC engines are influenced by the fuel injection rate. The study of fuel injection rate profile thus becomes essential to improve engine performance. In the present study, the injection rate of GDI injectors was measured in terms of the instantaneous mass flow rate of fuel. A setup was fabricated to obtain the injection rate based on Bosch tube method. Multi-hole GDI injectors of two different manufacturers were used in this study and their performances were measured up to 175 bar of injection pressure. The injector energizing current, wave pressure and rail pressure data were acquired at the rate of 500 kHz on a common time scale. The injected mass value per pulse, obtained by integrating the discharge rate profile was compared with the average values of mass injected measured using a mass balance for both the injectors and their performance were compared. The hydraulic delay measured during injector closing was found to be more than that during injector opening for both the injectors. Injection rate values for any given energizing time was found to be higher for one of the injectors by both the rate profile method and the mass balance averaging method. © 2015 International Conference on Liquid Atomization and Spray Systems. All rights reserved.