A Comprehensive Analysis of the Torque Behavior of a Flex Fuel Spark Ignition Engine

Since the debut of the spark ignition engines about 150 years ago, the understanding of an engine torque production has been widely investigated in many engine combustion research laboratories around the world. The effects of an engine geometric and operation parameters like, for instance, throttle angle, spark advance, fuel octane rating and compression ratio have been one of the main goals of these studies. A modern torque model based engine control software, which is able to predict and control engine torque for a given operating condition, makes use of these engine researches’ findings. A new variable which has been added recently into the torque generation study is the ethanol content fuel, in order to suit flex fuel engines application. This paper presents the results of an analysis conducted with a flex fuel engine running on Brazilian gasohol (E25) and hydrous ethanol (E100) fuels. The effects of engine load, spark advance and fuel ethanol content in torque production are discussed. A model to predict the engine torque based on these control parameters is proposed and the results are compared to the actual engine figures.