VARIABLE VALVE TIMING AS A MEANS TO CONTROL ENGINE LOAD

This work is the continuation of theoretical research which proposed a method to control the engine load by means of variable valve timing. As can be predicted, the early closing of the inlet valve allows lowering of 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 capacitor in the timing system, so the free closing stroke of the valve is determined by its spring. A special 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. (Author/TRRL)