The use of alternative fuels is important to address the issues of reducing dependence on unstable petroleum supplies, and reducing harmful emissions that can lead to global warming. This paper focuses on a comparative energy balance on a four cylinder turbocharged diesel engine operating on diesel and biodiesel fuels. The diesel fuel tested was a standard No. 2 diesel fuel and the biodiesel used was 100 percent soy methyl ester (B100) supplied by Peter Cremer North America. Steady-state tests were run to experimentally determine how input energy in the form of fuel was appropriated throughout the engine. The transfer of energy was measured for losses to the engine coolant and exhaust, usable power output, as well as minor and unaccounted losses. Temperature measurements were taken using type-K thermocouples, the power and torque outputs were measured with an AE 250 eddy current dynamometer, and the fuel consumption rate was measured using a scale and digital stop watch. The coolant and air flow rates were also monitored with respective flow meters. The laboratory environment was monitored to insure operator safety as well as consistent operating and atmospheric conditions. An energy balance algorithm was constructed to analyze logged data from the experiments and insure that the proper amount of readings was taken to insure accurate results. The results showed that biodiesel and diesel fuel have almost the same energetic performance. The nominal values of the energy distribution showed that input energy from biodiesel was distributed 37.4%, 31.1%, and 29.6% to the major areas of coolant, exhaust, and power output, respectively. Similarly the input energy from diesel was distributed 37.5%, 31.4%, and 29.2% to the major areas of coolant, exhaust, and power output, respectively. The respective differences in those nominal values between the biodiesel and diesel fuel are −0.1%, −0.3%, and 0.4%. The uncertainty analysis showed that there was not a statistically significant difference in the energy distribution. The results also showed a strong correlation between the ambient air entering the engine and many of the other measured temperatures. Conclusions about the laboratory environment and testing procedures have been made from analysis of the collected data. The energy balance study outlined in this paper helped validate the overall engine diagnostic testing system. It also helped establish guidelines and procedures for future testing because this testing platform will be used for future work in performance and emissions testing of algal-based biodiesel which is the program’s overall goal.

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