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For compression ignition (CI) engines, two of the fuel injection parameters affecting the engine's performance and emissions formation, are fuel injection timing (FIT) and injector opening pressure (IOP). Other such parameters include the number of injections, rate of injection and injection pattern, etc. In the present study, a multi-cylinder, turbocharged, four-stroke, direct injection (DI) diesel engine was used to investigate the combined influence of FIT and IOP on performance and emissions characteristics. The experimentation was conducted for two IOPs (250 and 300 bar) with four FITs such as 20°, 23°, 26°, and 29° before top dead center (BTDC) at different engine speed and load conditions. To obtain the emissions characteristics, the engine was tested in accordance with the 8-mode steady-state cycle. Moreover, 250 bar and 23° BTDC were the original IOP and FIT, respectively. For all IOP conditions, in comparison to the results with the original FIT, the advancement or retardation in FIT provided the negative results in terms of brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC). Increasing the IOP from 250 to 300 bar, improved the performance parameters for retarded and original FITs (20° and 23° BTDC) and caused the deterioration in performance for advanced FITs. In terms of emissions characteristics, filter smoke number (FSN) and emissions of carbon monoxide (CO) and unburned hydrocarbon (UHC) decreased on advancing the FIT and increasing the IOP. On the other hand, oxides of nitrogen (NOx) and carbon dioxide (CO2) increased on advancing the FIT and increasing the IOP for all experimental conditions. The maximum improvement in the performance of the engine was observed at increased IOP with the original FIT. The original IOP with retarded FIT resulted in the minimum NOx and CO2 with a significant reduction in performance. Furthermore, improvement in performance and reduction in emissions were observed when the engine was operated at higher IOP and retarded FIT. [ABSTRACT FROM AUTHOR]