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The present article shows the effect of the mass and friction reduction inside the engine over the carbonic gas emission reduction in the atmosphere. Authors have confirmed that the mass reduction and low friction in the internal components of the OTTO cycle engine, achieved by exhaust and admission valves re-dimensioning and sealer's substitution can help to reduce fuel consumption and, consequently, CO2, the main greenhouse effect gas. It is exposed and discussed different measurements of torque and power curves, friction power, and specific fuel consumption compared in the same engine without the proposed improving actions.

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.

The advent and high market share of the flex fuel were viable also due to the use of software to identify the type of fuel via the oxygen sensor signal manipulation. However, these routines are subjected to a non observable system, especially in conditions where the fuel enters the combustion chamber by ways other than the injectors, as the blow-by system, which leads the gases from oil pan. These gases can present high alcohol concentration, which evaporates from the contaminated oil, mainly after starts at low temperatures, causing the shifting of the oxygen sensor signal and consequently the misinterpretation of the fuel type flowing into the engine. This paper has the objective to propose an estimation method for the mass of fuel in the oil, using separate simplified physical models for the oil contamination and for the alcohol evaporation processes.