-In this study, an experimental study of the effects of injection timing on nitrogen oxide (NO x ) emissions of a low heat rejection (LHR) Turbo charged direct injection diesel engine was conducted. The injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NO x emissions analysis. For the original injection timing of the 20 • before top dead centre, the brake Specific fuel consumption value of the LHR engine was approximately 6% lower than the original engine. NO x emissions were also higher (about 9%) than the original engine. To reduce NO x emissions released by diesel engines, the method of injection timing retard was utilized. Thus, the LHR engine was tested for two different injection timings; 18 • and 16 • crank angle before top dead centre (BTDC), at the same engine speeds and load conditions. The results showed that the BSFC and NO x emissions were reduced 2% and 11%, respectively by retarding the injection timing. Optimum injection timing for the LHR engine was obtained through decreasing by 2 • BTDC.