Nowadays, due to the environmental problems caused by pollution and high fossil fuels prices, the study on the internal combustion engines have attracted many researchers. Investigations show that low-temperature combustion engines play a very effective role in increasing efficiency and reducing emissions. In this research, the effects of diesel fuel injection timing on the performance characteristics of the engine and reducing its emissions were experimentally studied. To do so, a single-cylinder engine equipped with a common rail injection system for controlling the pressure was used. Gasoline fuel was injected through the injector installed in the inlet manifold. The gasoline entered the cylinder as a low-reactivity fuel with inlet air, while the diesel fuel was injected into the cylinder as a high-reactivity fuel by a common rail system and high-pressure injector. Diesel fuel was injected into the cylinder at − 50°, − 40°, − 20°, and − 10° before top dead center (bTDC). The results show that the engine minimum and maximum brake power and efficiency output were observed in the fuel injection timings of − 10 and − 40 bTDC, respectively. Also, it was found that advancing the injection timing increases the ignition delay and plays a very important role in the combustion phasing quality. Besides, findings show that advancing fuel injection timing has a significant effect on NOx and particulate matter (PM) emissions. The lowest and maximum amount NOx emissions occur at the injection timings of − 50° and − 10°, respectively, while for PM emission these values are − 40 and − 50, respectively. According to the results, the injection timing could be one of the most important parameters for controlling the engine that will increase efficiency and reduce emissions.