Flex Fuel Engine - Influence of Fuel Composition on the CA50 at Maximum Brake Torque Condition

The automotive industry usually adopts the crankshaft angle between 8° and 10° after piston top dead center for the CA50 (crank angle of 50% of mass fraction burned) in order to set the maximum break torque spark timing calibration in Otto cycle engines. There are few studies of the influence of fuel composition, such as the ethanol content, on the CA50 at the maximum torque operating condition. The subject is relevant to the extent that the fuels used in the Brazilian domestic market are different from those usually adopted abroad. The Brazilian gasoline must contain, by law, a volumetric percentage between 18% and 27% of anhydrous ethanol in its composition and, currently, this level is set at 27%. The introduction of flex fuel vehicles in the domestic market in 2003, which now represent most of the new vehicles production in the Country, allowed the use of any blend of national gasoline and hydrous ethanol. This significantly expanded the range of fuel properties variation. This fuel flexibility influences the design, calibration and efficiency of internal combustion engines. The present work is a study to assess more information on the influence of different fuels on the CA50 at maximum break torque spark timing calibration. This knowledge may help in researches related to the development of fuels, internal combustion engines and in the search for greater engine efficiencies, using different fuels.