Abstract
The most important event and result of the last ten years might have been the engine management systems at the development of the vehicle engines. This has enabled to optimalize the motoric processes in the light of each most important parameter affecting the characteristics of the formation of mixture and combustion.
As a third paramater, in addition to the mixture grade, thus the air-to-fuel ratio as well as the ignition time, the possibility is provided to intervene in the process of change in chargeas well in order to meet the standards increasingly tightened up regarding the limitation of the harmful substances in addition to the good comsumption and performance data of the engine.
Depending on the construction shape, the up-to-date, variable-parameter valve timing systems have needed mechanisms with various measures but practically more and more complicated ones. Simultaneously, the rating used to operate the valves will figure out the significant portion of the frictional losses decisively affecting the mechanical efficiency of the engine. See figure No. 1.