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Engine Performance and Exhaust Emissions  from Small and Large Diesel Engines Using Soy Bean Oil Biodiesel and Blends

Bjorn S. Santos2 and Sergio C. Capareda3


The objective of this study  was to evaluate performances and exhaust emissions of two engine sizes and injection systems (3-cylinder YANMAR engine with indirect injection and 4-cylinder John Deere engine with direct injection) using biodiesel fuel derived from soybean oil. Engine power tests were conducted in accordance with SAE Standard Engine Power Test Code for diesel engines (SAE J-1349). Test fuels included standard no. 2 diesel and four biodiesel fuels comprising of 5%, 20%, 50% and 100% soybean oil biodiesel. Results of the experiments showed that the peak power produced for both engines using different blends of soybean oil biodiesel has no significant difference compared to that of the standard no. 2 diesel. However, the brake-specific fuel consumption increases as the percentage of biodiesel in a blend           increases. Such an increase can be best described by the B50 SME and B100 SME test fuels. Biodiesel blending also increases the thermal efficiency of a small engine but this effect becomes minimal as the     engine size is increased and injection system is changed. Furthermore, there was a significant reduction in the emissions of pollutant concentrations (i.e.CO2, CO, and SO2), with the exception of NOx emissions, as the percentage of biodiesel in a blend increased. Generally, NOx emissions are higher for biodiesel and blends at low  engine speed conditions for both engines.

Keywords: biodiesel, biodiesel blends, diesel engine, engine performance, engine exhaust emissions,       soybean methyl ester

 1Paper presented at the 2008 Annual National Convention of the American Society of Agricultural and Biological Engineers ASABE), June 29 to July 2, 2008, Rhode Island, USA. 2Graduate Research Assistant and 3Assistant Professor, Biological and Agricultural Engineering Department, Texas A&M University, College Station, Texas, USA.