Abstract: In this study, experimental tests were carried out to explore the performance, combustion and emissions by modifying the different nozzles hole size injectors such as (3 holes×Ø = 0.20 mm (modified)), (3 holes×Ø = 0.28 mm (Base)) and (3 holes×Ø = 0.20 mm (modified)). The experiments are performed on Kirloskar 4-stroke computerized solitary cylinder diesel engine fueled with diesel at 1500 rpm, water-cooled direct injection diesel engine with eddy current dynamometer with the standard injection timing of 23° bTDC with an injection pressure of 210 bar was maintained constant throughout the experiment. From the results, it was observed that among all the three different nozzles (3 holes×Ø = 0.20 mm (modified)) improves the vaporization, atomization and air-fuel mixing which leads to shorter combustion duration and appreciable results were seen in performance, combustion and in emissions. But the only weakness was NO increasing with x smaller orifice Nozzle Hole Diameter (NHD).