Recently, the demand for comfort with environmental protection has been increasing considerably. This is not only the concern of industry, but also of the entire society. Therefore, it's required as an indispensable element for engines as power sources of machineries to have characteristics such as low noise and pollution output, as well as high performance and reliability.There have been various studies on this theme and steady achievements have been made so far. However, the conventional technologies have their limitations, having reached the highest level that they can possibly achieve, so now new technologies and new thinking are needed to meet the environmental theme.This report discusses a new approach to the 92.4mm Stroke Series next generation engines, which have reduced noise by using noise quality analysis and other techniques. This report also presents the optimization of the combustion system by utilizing numerical simulation techniques such as fluid flow analysis.