Variable valve timing as a means to control Otto engine load

This work is the prosecution of a theoretical research which proposed a method to control the Otto engine load by means of a variable valve timing. As can be predicted, the early closing of the inlet valve allows to lower the engine load with reduced air-throttling, so that a fuel economy can be obtained. A hydraulic system was designed to perform the variable valve timing as follows. A rotating distributor, controlled by the camshaft, empties a capacity in the timing system, so the free closing stroke of the valve is determined by its spring. A particular device virtually eliminates the valve impact against its seat. The hydraulic system was applied to a single cylinder engine and bench tests were carried out so as to allow a comparison between the engine performances obtained by air-throttling and those obtained by variable valve timing. Preliminary experimental results are reported and discussed.