Fuel injection system influences the spray characteristics to achieve faster combustion and better control over emissions. The combination of orifice number, diameter, injection duration, and rotation is suggested for better emission control and efficiency. In the present work, a novel self-rotating injector is designed and fabricated. Simulation is performed in three-dimensional closed-cycle geometry of a 661 cc diesel engine for static as well as rotating fuel injection having three, five, and nine holes by varying the rotational speed of 1500 and 2500 rpm, orifice diameter, and injection duration to ensure the same injection velocity. The three-hole rotating cases were studied and compared with static numerical simulation. The results found that due to the rotational effect, the engine’s thermal efficiency improved by 3.82% and 5.11% while the NOx emissions decreased by 2.34% and 5.57% for 1500 and 2500 rpm, respectively, at the cost of carbon monoxide and soot emissions. Increasing the rotational speed was found to improve temperature uniformity at higher speeds, thus increases the efficiency and lower NOx. By increasing the number of orifice holes, it was observed that both thermal efficiency and NOx increased. Controlling the primary and diffusion combustion, it is possible to improve the efficiency without increasing NOx emissions. This was possible with a combination of rotating injectors and varying the start of injection. The fabricated self-rotating nozzle based on the above simulations was found to perform better than the static injector under no-load conditions.