Effects of MTBE usage at high compration ratio on otto engine performance

In this study, effects of Methyl Tertiary Butyl Ether (MTBE) addition (10, 20 and 30 %in volume) to unleaded gasoline fuel on engine torque, specific fuel consumption, andthermal efficiency have been experimentally investigated. A Hydra single cylinder,spark ignition, fuel injection engine was used in different compression ratio (10/1 and12/1) at full load and different engine speed. Ignition timing was set at maximum enginetorque for each engine speed. The effects of MTBE addition were also tested at differentvariable throttle positions, engine speed, advanced timing (5-36º CA), over wide relativeair/fuel ratio (λ=0,8-1,2) in order to evaluate effects of engine operating parameterschanges. However, variable engine speed tests were made for comparison with fourcylinder Ford engine which has 8,8/1 compression ratio at different engine speed andfull throttle. Experiments show that, maximum increment for 10/1 and 8,8/1compression ratio on engine torque was obtained at whole engine speeds when theengine fueled with %10 MTBE blends. In 12/1 compression ratio, improvementsobserved on engine torque with MTBE addition running at low and high speeds.Improvement on thermal efficiency was provided in all engine speed by MTBE addition.The best value of the thermal efficiency obtained with 20% MTBE addition at 10/1 and12/1 compression ratios. In experiments which depend on different throttle positions,maximum engine torque and minimum specific fuel consumption achieved with 10%MTBE blends. In different ignition timings, all MTBE blends gave better thermalefficiency and low specific fuel consumption values than unleaded gasoline when bothcompression ratios. While maximum thermal efficiency and minimum specificconsumption values were observing with 10% MTBE blends in 10/1 compression ratio,it also achieved with 20% MTBE blends in 12/1 compression ratio. The torque valuewith unleaded gasoline in 12/1 compression ratio appeared higher than other, whileMTBE blends were giving high torque values for 10/1 compression ratio in differentignition timings. The highest thermal efficiency and lowest specific fuel consumptionvalues for 10/1 compression ratio achieved with 10% MTBE blends, and with MTBE20for 12/1 compression ratio.Key Words : Oxygenated gasoline fuels, MTBE-Gasoline blends, Spark ignitionengine, Engine performance