The pistons are still running, taking airfrom the partially closed intakemanifold. The intake manifold betweenthe throttle and the combustion chamberhas a partial vacuum, resisting thesucking and pumping action <strong>of</strong> thepistons, wasting energy. Automotive<strong>engine</strong>ers refer to this phenomenon as"pumping loss". The slower the <strong>engine</strong>runs, the more the throttle butterflycloses, and the more energy is lost.WORKING OFVALVETRONIC ENGINE Working Of OrdinaryEngineIn <strong>engine</strong>s without <strong>valvetronic</strong><strong>technology</strong> fuel injection systemsmonitor the volume <strong>of</strong> air passingthrough the throttle butterfly anddetermine the corresponding amount <strong>of</strong>fuel required by the <strong>engine</strong>. The largerthe throttle butterfly opening, the moreair enters the combustion chamber.At light throttle, the throttlebutterfly partially or even nearly closes. intake valve with throttle plate. the supply <strong>of</strong> the fule/airmixture is controlled by thethrottle plate. valve lift isunchanged. Working Of Valvetronic EngineCompared with conventional twin-cam<strong>engine</strong>s with finger followers,Valvetronic employs an additional
eccentric shaft, an electric motor andseveral intermediate rocker arms, whichin turn activates the opening and closing<strong>of</strong> valves. If the rocker arms pushdeeper, the intake valves will have ahigher lift, and vice-versa. Thus,Valvetronic has the ability to get deep,long ventilation (large valve lift) andflat, short ventilation (short valve lift),depending on the demands placed on the<strong>engine</strong>. intake valve with <strong>valvetronic</strong>. the fuel/air mixture is controlled by avariable valve lift, without a throttle plate.Cylinder heads with Valvetronic use anextra set <strong>of</strong> rocker arms, calledintermediate arms (lift scaler),positioned between the valve stem andthe camshaft. These intermediate armsare able to pivot on a central point, bymeans <strong>of</strong> an extra, electronicly actuatedcamshaft. This movement alone, withoutany movement <strong>of</strong> the intake camshaft,can open or close the intake valves.The Valvetronic system is basedon BMW's established double VANOSsystem, which steplessly varies thetiming <strong>of</strong> both the inlet and exhaustcams. However, the Valvetronic systemadds variable valve lift to the inlet cam,achieved by the use <strong>of</strong> a lever positionedbetween the camshaft and the inletvalves. Valvetronic varies the timing andthe lift <strong>of</strong> the intake valves. TheValvetronic system has a conventionalintake cam, but it also uses a secondaryeccentric shaft with a series <strong>of</strong> levers androller followers, activated by a steppermotor. Based on signals formerly takenmechanically from the accelerator pedal,the stepper motor changes the phase <strong>of</strong>the eccentric cam, modifying the action<strong>of</strong> the intake valves. An additionaleccentric shaft alters the lever's distancefrom the camshaft, with the eccentric'sposition determined by a worm drivefrom an electric motor. The position <strong>of</strong>the lever converts the cam action into asmaller or larger valve lift, as requestedby the <strong>engine</strong> management system.