Due to the changes in the environment surrounding the industrial engine market, such as strengthening of exhaust emissions regulations of diesel engines and production increase of shale gas, the needs of the gasoline, LPG or natural gas fueled engines are growing.In the North American market, exhaust emissions regulations of industrial SI engines are getting strict. On the other hand, European market and developing countrys' market have no exhaust emissions regulations for SI engines. Therefore it is necessary to develop the engines which meet the needs of each region. Based on the existing diesel engine, we developed the two types of SI engine WG2503 (displacement 2.491L) simultaneously. In this paper, approaches and technologies used for the development of these models are explained.To secure the high torque characteristics, its combustion chamber configuration was optimized. Ignition timing was optimized according to the fuel types. By these approaches, the frequency of knocking was reduced and high torque characteristics at medium and low speed range was realized. Because industrial engines are installed on the various applications, engines must be compact and installed easily. To meet these requirements, we have developed the compact inlet manifold and the compact exhaust manifold. This also secured installation compatibility with the original diesel engine model.Long maintenance intervals are also required for industrial engines. Prolongation of oil change intervals is one of the most important items of the maintenance intervals. We have challenged to reduce oil carry-over by changing the structure of the head cover.