Influence of the Cooling Liquid Temperature on the Fuel Consumption and Performance of an Otto Cycle Flex Fuel Engine

Due to the increasing importance of vehicle energy efficiency, design changes on flex fuel engines aiming fuel consumption and CO₂ emissions reduction becomes priority. It is known that, due to chemical difference between hydrated ethanol (E100) and commercial gasoline (E22), parameters as combustion pressure, burn speed and knock tendency vary according to the fuel and are decisive for the engine thermal efficiency. This study has the objective to show and quantify the influence of the cooling liquid temperature in these parameters and on the thermal, mechanical and global efficiencies of an Otto flexible fuel engine, aiming to observe opportunities of fuel consumption reduction and performance improvement, as a way to compensate the fixed compression rate of flex engines. The results show that it is possible to have better efficiency in partial and full loads, adjusting the cooling liquid temperature according to the used fuel.