Journal of the Korean Society of Marine Engineering, Vol. 34, No. 3, pp. 351～359, 2010(ISSN 1226-9549) Journal of the Korean Society of Marine Engineering, Vol 34, No. 3, 2010. 5 / 351 Performance Anal y sis and Emission Characteristics of a Bi-fuel Using Spark Ignition Engine Md. Iqbal Mahmud 1 ․Haeng-Muk Cho† (Received January 5, 2010; Revised March 8, 2010; Accepted May 4, 2010) Abstract：Bi-fuel system in a spark ignition engine (SIE) is a rising phenomena in today’s automobile technology. In a gasoline driven vehicle, alternatively adoption of compressed natural gas (CNG) could be used as a potential substitute to meet the energy requirement and this is possible by some minor changes in the hardware of the existing engine. Gasoline engine is widely used in the passenger cars, light, medium and heavy duty vehicles but the consumption status of the petroleum is decreasing worldwide and at the same time environmental pollution from automobiles is seriously establishes as a threat for every nation in respect to global warming and climate changes. Now-a-days most vehicles operate using CNG for its popularity stems, clean burning properties and cost effective solution compared to other alternative fuels. It refers as a good gaseous fuel because of its high octane number and self ignition temperature. Though the power output is slightly lesser than the gasoline fuel; its thermal efficiency is better than the gasoline for the same SIE. The research paper highlights the reduction of CO, reasonable outcomes of HC emissions with minor increase in NOx emissions compared with the gasoline fuel to bi-fuel mode in the SIE that meets the emission challenges. Key words：Spark Ignition Engine (SIE), Compressed Natural Gas (CNG), Gasoline, Bi-fuel, Emissions * Corresponding author (Department of Mechanical Engineering, Kongju National University, Email : Phone: +82-41-521-9287; Fax: +82-41-551-0376) 1 Department of Mechanical Engineering Kongju National University 1. Introduction Emissions from automobiles are a serious issue in today’s world. Considering the issue, auto manufacturers are developing the technologies for minimizing the vehicular exhaust. International and governmental regulations of specifying exhaust limit led to researchers and scientists to invent advanced technology to reduce such emissions. Environmental protection and energy conservation have become a major issue at present. In this regard, Kyotoprotocolwas initially adopted on 11 December 1997 in Kyoto,Japantothe United Nations Framework Convention on Climate Change (UNFCCCorFCCC). In 2012 the Kyoto Protocol to prevent climate