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The vibrations related to powertrain stiffness contributes strongly to the vehicle acoustic comfort. The connection between the engine and transmission influences the vibrational powertrain behavior. The subject of this work is the numerical and experimental behavior evaluation of an powertrain vibration behavior under influence of the connection between an internal combustion engine and the transmission. Were evaluated three powertrain configurations with different levels of stiffness. The results (based on natural frequencies modes) matched the experimental evaluations at vehicle

Along the last thirty years one of the challenges is to develop an engine working with ethanol with the same performance and characteristics of gasoline engines functioning at low temperatures. In Brazil the production expansion of flex fuel engines is the main motivation for technology development and research to improve the engine cold start and functioning, when using ethanol. The use of gasoline as an auxiliary in the cold start system is now the main characteristic of this system. In this work the performance of a new cold start system is analyzed. Tests were performed in a vehicle and the results show the potential of the new technology.

The increasing number of flex fuel vehicles using pure or mainly ethanol when mixed with gasoline led to a necessity of an auxiliary cold start system. These systems are based on introducing gasoline during the engine's cold phase. The researches lead to find an alternative to avoid using gasoline at cold start systems. This works presents a numerical analysis of the flow and heat transfer in a cold start system, using computational fluid dynamics. A prototypal vehicle was used to validate the simulations. The tests were done at controlled ambient temperatures: 0°C for cold start measurements and 25°C at chassis dynamometer to run the FTP75 emission cycle. The numerical data were validated and the results showed the possibility to get a temperature high enough to assure fuel combustion with emissions benefits.

The use of pure ethanol or the prevailing of it in the mixture with gasoline in flex fuel engines, led to a necessity of an auxiliary system to the cold start and engine functioning. Ethanol chemical properties can be used to explain this necessity. Ethanol is been used in Brazil for more than 30 years and many researches give support to the cold start technologic evolution. The cold start system enables the gasoline introduction into the intake manifold of flex fuel engines, when vehicles are using pure ethanol or a mixture with more ethanol than gasoline. The researches challenge is to find a way to start an engine using ethanol without the use of the cold start system using gasoline. This works presents a numerical analysis of the flow and heat transfer in a cold start system, using computational fluid dynamics. An experimental test bench developed to study a start cold system heating air and ethanol.

The objective of this work is to do an experimental analysis of mass and stiffness (rigidity) parameters alteration and its influence in the valve train behavior. The valve train vibration contributes considerably to noise level and is related to acoustic comfort, performance and durability of the cylinder head. Three valve train configurations were used to a comparative analysis. The first configuration was the reference (base line). In the second configuration the mass of the group was increased. In the third configuration a different valve spring was used to alter the rigidity of the group. Acceleration sensors were installed in strategic positions (inside and outside) of the cylinder head to measure vibration levels in vertical and horizontal plans that permitted a comparison between the configurations results.

Cold start systems provide the introduction of gasoline inside the engine intake system during cold start and warm-up acceleration, as ethanol fuel shows engine operation difficulties at low temperatures. Despite the technological evolution, traditional cold start systems may present problems mainly related to flow control and gasoline distribution to the engine cylinders hindering cold start and warm-up operation with the increasing of emissions levels and fuel consumption. The cold start system used allows for simultaneous gasoline introduction through calibrated orifices in the four conduits of the intake system. Adjustment of gasoline flow is made by an electronic fuel injector. The objective of this work is to analyze numerically and experimentally the gasoline flow in an auxiliary cold start system for vehicles with engines using ethanol or ethanol-gasoline blends (flex fuel).

The gasoline injection system used as an auxiliary during cold start of ethanol-fuelled engines has been improved to reduce exhaust emissions levels. In substitution to the conventional system, which introduces gasoline in the throttle body through a calibrated pipe in a hole, an electronic fuel injector and other peripheral components have been used to inject gasoline. Experiments were carried out in an ethanol-fuelled vehicle powered by a 1.0 liter engine to measure regulated exhaust pollutant gases concentrations, to compare the modified system to the conventional one. The tests were according to FTP-75 test cycle, which simulates a typical urban travel including cold start and acceleration during warm-up. The results showed that the concentrations of aldehyde, hydrocarbon, carbon monoxide and oxides of nitrogen emissions were simultaneously reduced when the modified system was used.