Reduction of Pumping Losses By the Use of a Variable Valve Timing System

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Abstract
In this paper, the advantages of using variable valve timing systems in order to decrease pumping losses are outlined. In the first part of the paper, the reduction of pumping losses through regulation of the engine load rate, by varying the time that the intake valve remains open, is justified by reasoning on ideal diagrams. In the second part, a proposed system to vary the valve timing diagram is described. This system consists mainly of a four-bar mechanism. Finally, the advantages and disadvantages of the proposed system are considered in the real engine by means of a calculation model. The conclusion is that with this system it is possible to obtain important improvements in the effective efficiency of the engine running at partial load.

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