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Variable Valve Actuation system (VVA) is a technology developed for improving fuel economy, reducing emissions, and enhancing engine performance mainly by reducing pumping losses. Many automakers have used VVA in their engine projects with excellent results. Usually, VVA systems are built to control the valve events in four different ways: changing the amplitude of the valve lift, the valve opening angle, the valve closing angle or a combination of those modes. A special attention at the calibration activity is needed to reach the optimum performance of this system, beyond this, it was necessary to develop a different way to calibrate, much more focused on the development of the combustion and the gas exchange process requiring an intense use of a pressure indicating system. This work presents a comparison between different way of actuation in combustion analysis of a VVA system on a spark ignition engine.

A burning process in a combustion chamber of an internal combustion engine is very important to know the maximum temperature of the gases, the speed of combustion, the ignition delay time of fuel and air mixture exact moment at which ignition will occur. The automobilist industry has invested considerable amounts of resources in numerical modeling and simulations in order to obtain relevant information about the processes in the combustion chamber and then extract the maximum engine performance control the emission of pollutants and formulate new fuels. This study aimed to general construction and instrumentation of a shock tube for measuring shock wave. As specific objective was determined reaction rate and ignition delay time of diesel, biodiesel and ethanol doped with different levels of additive enhancer cetane number. The results are compared with the ignition delay times measured for other authors.

This work describes an updated cold start system for ethanol fuelled engines using an electronic gasoline injector. The new system is a substitute to the conventional cold start system that employs a calibrated hole for gasoline introduction in the intake pipe. The new system is constituted by a gasoline reservoir, electrical fuel pump, fuel injector, fuel filter, and solenoid valve frequency controller. Experiments have been carried out in a production 1.0-liter, four-cylinder, ethanol-fuelled engine, submitted to transient emissions tests after cold start. The results show that the updated system reduces the cold start period by 31% in comparison to the conventional system. Acceleration after cold start was also improved, with gasoline consumption reduction of 67%.