Together with renewed legislations, the automotive industry and research centers continue their efforts to develop internal combustion engine (ICE) technologies that consume less fuel and more environmentally. The basic step in developing efficient and environmentally ICEs is to ensure that the parameters affecting the in-cylinder combustion and the exact combustion. Although there are many parameters that affect each other, such as fuel consumption, emissions and noise, the main source of these results is the in-cylinder combustion event. Control of combustion initiation, ignition delay, and combustion must be well understood as all output will affect it. Although many parameters in today's ICE technology such as fuel temperature are controlled by sensors and instantly evaluated with Electronic Control Unit (ECU), optimization of feedback is provided by analyzing the factors affecting ignition delay. The factorial design method is used in this optimization study which examines the parameters of engine speed, load and fuel temperature. In this optimization study, it has been found that the engine speed, load and fuel temperature significantly influence ignition delay in different sizes.