Combustion and Emissions of Ethanol Fuel (E100) in a Small SI Engine

An air-cooled, four-stroke, 125 cc electronic gasoline fuel injection SI engine for motorcycles is altered to burn ethanol fuel. The effects of nozzle orifice size, fuel injection duration, spark timing and the excess air/ fuel ratio on engine power output, fuel and energy consumptions and engine exhaust emission levels are studied on an engine test bed. The results show that the maximum engine power output is increased by 5.4% and the maximum torque output is increased by 1.9% with the ethanol fuel in comparison with the baseline. At full load and 7000 r/min, HC emission is decreased by 38% and CO emission is decreased 46% on average over the whole engine speed range. However, NOx levels are increased to meet the maximum power output. The experiments of the spark timing show that the levels of HC and NOx emission are decreased markedly by the delay of spark timing. When the ignition timing is postponed from 37 °CA to 31 °CA BTDC, HC and NOx emission levels are decreased by 14.7% and 30.4%. At the same time, the power output is only decreased by 3.8%. Under the idle condition, CO emission is decreased by 20.7% and NOx emission is decreased by 84.3% by using ethanol fuel. HC emission remains unchanged.