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In order to improve the cold flow properties of coconut oil biodiesel and to reduce the lifecycle CO2 emission by using bio-alcohol at biodiesel manufacturing, varying the types of alcohol used at transesterification was examined. The pour point of coconut oil ester decreases as the carbon number of alcohol increases. Among 5 ester fuels, the pour point of coconut oil isobutyl ester (CiBE) made from isobutanol is lowest, −12.5 °C, compared to that of coconut oil methyl ester (CME), highest, −5 °C. The pour point of coconut oil 1-butyl ester (CBE) is −10 °C, second lowest. Furthermore, CBE, CiBE, CME and JIS No.2 diesel fuel (gas oil) were tested using a DI diesel engine. CBE and CiBE have shorter ignition delay compared to the gas oil although slightly longer than CME. CBE and CiBE have the same thermal efficiency and NOx emissions compared to the gas oil. HC, CO and Smoke emissions of coconut oil ester fuels slightly increase when the ester molecule carbon number increases.

The present study investigated the effect of boost pressure on the operation of a small single cylinder DI diesel engine equipped with a jerk type injection system fueled by different biodiesel fuels. The study employed a Roots blower type supercharger driven by a motor, and the boost pressures were varied from 100 kPa (naturally aspirated condition) to 140 kPa. The experiments used three kinds of biodiesel: rapeseed oil methyl ester (RME), soybean oil methyl ester (SME), and coconut oil methyl ester (CME). Further, a blended fuel with 60% (mass) CME and 40% 1-butanol (represented as CMEB) was also used. The influence of the boost pressure on the engine performance, combustion characteristics, and exhaust emissions with the abovementioned four biofuels were examined and compared with standard JIS No. 2 diesel fuel.