<p>This study delves into the theoretical exploration of the effects of injector and orifice arrangement, spray angle, and orifice size on combustion and emission characteristics of horizontal opposed two-stroke engines. By employing numerical simulations, the research systematically investigates how variations in these parameters influence engine performance and emissions. The findings underscore the significance of injector and orifice configuration in optimizing fuel spatial mixing and atomization, resulting in improved indicated thermal efficiency and indicated mean effective pressure. However, it is noted that while emissions of HC, Soot, and CO can be maintained at low levels by injector and orifice configuration, NO_<i>x</i> emissions tend to be relatively higher. Moreover, the study highlights the impact of spray angle on combustion dynamics, where an optimum spray angle is identified for achieving peak thermal efficiency and effective pressure due to the improvement between spray distribution and impingement. Additionally, the study reveals the critical role of nozzle diameter in combustion and emissions control, with an optimal diameter leading to enhanced thermal efficiency and reduced emissions of Soot, HC, CO, and CO₂ to some extent. Overall, these findings offer valuable insights into optimizing engine performance and emissions control strategies in horizontal opposed two-stroke engines, guiding future research and development efforts in the field.</p>