In this study, large-bore diesel engine combustion was modeled using development combustion model Extended Coherent Flame Models 3 Zones (ECFM-3Z). During this work, the study was made about an engine configuration with compression, spray injection, combustion and emission of the diesel engine. Prediction of in cylinder combustion phenomenon, effects of turbulence levels, flow structures and emission modeling have an importance in designing efficient engines. Effects of in-cylinder flow structures, fuel injection and design parameters were investigated for the engine performance and emission results. The results agree broadly with experimental and computational studies. As a result, it is aimed to find out the flow structure, spray, combustion and emission characteristics of the large-bore diesel engine. In a precombustion chamber structure, it is seen that controlled combustion starts and then high-pressure gas mixture uniformly spreads into the main combustion chamber.