Indian Journal of Engineering & Materials Sciences Vol. 18, June 2011, pp. 204-210 Comparative study of engine performance and exhaust emission characteristics of a single cylinder 4-stroke CI engine operated on the esters of hemp oil and neem oil S S Ragit a *, S K Mohapatra a & K Kundu b a Department of Mechanical Engineering, Thapar University, Patiala 147 004, India b Mechanical Engineering Research and Development organization, Ludhiana 141 006, India Received 6 October 2010; accepted 10 June 2011 In this study, the biodiesel produced from selected non-edible oils are prepared by a method of alkaline catalyzed transesterification. Esters of non-edible vegetable oils such as hemp oil and neem oil are potentially effective diesel substitute. The study is carried out to investigate the performance and emission characteristics of selected fuel in a stationary single cylinder, four stroke, naturally aspirated direct injection diesel engine and compare it with mineral diesel. The engine performances (thermal efficiency, brake specific fuel consumption, brake specific energy consumption, and exhaust gas temperature) whereas exhaust emissions (oxides of nitrogen, unburned hydrocarbon and smoke opacity) are evaluated. The experimental results in each case are compared with baseline data of mineral diesel. Significant improvements have been observed in the performance parameters of the engine as well as exhaust emissions. The results show a 45.07% reduction in NOx, 84.42% reduction in HC, 28.35% in smoke but brake thermal efficiency increased slightly (0.19%) at full load for hemp biodiesel, 6.06% reduction in NOx, 2.59% reduction in HC, 18.39% reduction in smoke at full load for neem biodiesel, respectively. The experimental study indicates that selected fuel can be used as a fuel in compression ignition engine without any engine modification. Keywords: Biodiesel, Fuel properties, Performance characteristics, Emission characteristics, Diesel engine, Comparative analysis Vegetable oil is one of the alternatives which can be used as fuel in automotive engines either in the form of straight vegetable oil, or in the form of ethyl or methyl ester. The energy needs of the world are increasing rapidly. The decrease in fossil fuels, emission pollution caused by them and increasing fuel prices make biomass energy sources more attractive. The increase in energy demand and decrease in oil reserves have been focused on biofuels. Biodiesel is a fuel that is manufactured from vegetable oils with the help of catalysts, and may be directly used in diesel vehicles with little or no modification. The biodiesel is reported to be sulfur-free, nontoxic, biodegradable oxygenated and renewable. And the characteristics of biodiesel are very close to diesel fuel 1,2 . And some are better than diesel such as higher cetane number, no aromatics, almost no sulfur, and more than 10% oxygen by weight, which reduce the emission of carbon monoxide, unburned hydrocarbon, and volatile organic compounds 3,4 . An experimental study is carried out to evaluate and compare the use of cottonseed oil, soybean oil, sunflower oil and their corresponding methyl esters. It shows that all tested biodiesel or vegetable oil blends, can be used safely 5,6 . An experimental study is also carried out to examine fuel properties, performance and emissions of different blends of methyl ester of pongamia, jatropha and neem in comparison to diesel fuel. The results indicated that diesel blends showed reasonable efficiencies, lower smoke, CO and HC 7 . The vegetable oil esters from edible oils may not be the right option for their substitution in diesel engine due to the lack of self-sufficiency of edible oil production in India. Hence, attention has been diverted to test the suitability of non-edible vegetable oils for diesel engine. With the abundance of forest and tree-borne non-edible oils available in India, limited attempts have been made to use the ester of selected non-edible as the alternative fuels for diesel engine 8 . In this experimental study, the biodiesel from different non-edible oils was produced by a method of alkaline-catalyzed transesterification. The objectives —————— *Corresponding author (Email:satish_ragit@yahoo.com)