The effects of neat biodiesel usage on performance and exhaust emissions from a small displacement passenger car diesel engine

The effects of using neat FAME (Fatty Acid Methyl Ester) in a modern small displacement passenger car diesel engine have been evaluated in this paper. In particular the effects on engine performance at full load with standard (i.e. without any special tuning) ECU calibration were analyzed, highlighting some issues in the low end torque due to the lower exhaust gas temperatures at the turbine inlet, which caused a remarkable decrease of the available boost, with a substantial decrease of the engine torque output, far beyond the expected engine derating due to the lower LHV of the fuel. However, further tests carried out after ECU recalibration, showed that the same torque levels measured under Diesel operation can be obtained with neat biodiesel too, thus highlighting the potential for maintaining the same level of performance. Moreover, the effects of FAME on brake specific fuel consumption and on engine out exhaust emissions (CO2, CO, HC, NOx and PM) were also evaluated at 7 different part load operating conditions, representative of the New European Driving Cycle. Both standard and specifically adjusted engine calibrations were evaluated for part load operating conditions, highlighting a 13% average rise of fuel consumption, on a mass basis, at same fuel conversion efficiency and CO2 emissions. A remarkable increase of CO and HC emissions at low load could be noticed, along with an almost negligible increase in NOx emissions when using a specifically adjusted engine calibration, and a considerable smoke emission reduction.