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The constant demand regarding vehicle efficiency and emissions improvement is a consequence of the expected very restrict emission regulations in the whole world. Despite the vehicle market being changing due to several new powertrain configurations options, such as hybrid and electric, internal combustion engines will still play an important role in future global vehicle market, due to its applicability in powertrain systems. Among other engine parameters, the geometric compression ratio has an important impact on the engine thermal efficiency and vehicle performance, however such parameter requires deep investigations in order to avoid operation with pre ignition and combustion knocking events. Vehicle simulation is widely used to select powertrain adequately, with respect to fuel consumption and performance.

The current quest for clean and renewable fuels has prompted the appearance of several bio-mass fuel alternatives. Ethanol is a renewable biofuel obtained from different agricultural crops. The main production process to obtain anhydrous ethanol consists of crop production, mashing and cooking, fermentation, distillation and chemical dehydration. Some attractive characteristics of ethanol as a clean energy source is the CO2 absorption through photosynthesis during the crop plantation phase and positive ethanol life cycle energy balance. Even though, ethanol production cost is still relatively high when compared to fossil fuels. Knowing that a large energy amount is spent in the distillation phase, the use of hydrous ethanol as fuel, with high water content, can be economically attractive. This paper compares the use of high water-in-ethanol volumetric content fuel, varying from 5% to 40%, in a naturally aspirated 0.668-L single-cylinder port-fuel injected spark-ignited engine.