An experimental investigation has been carried out to examine the diesel engine combustion noise and engine roughness when palm oil methyl esters biofuel is used in a diesel engine. A reference case has been tested when diesel fuel is used and another case when crude palm oil is used. A variable compression research diesel engine Ricardo E6 has been used throughout the current work. The effects of engine speed, engine load, injection timing and compression ratio have been experimentally scrutinized. The results presented included the he maximum combustion pressure rise rate, the maximum sound pressure level at the different engine conditions. The diesel engine exhibited less combustion noise, less engine roughness when palm oil methyl esters biofuel is used. The engine exhibited even less noise when crude palm oil is used, though the viscosity is not practically acceptable.
