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Discussion Starter · #1 ·
hi there just been reading up on valve tronic engines it says on the artical i have been reading http://www.usautoparts.net/bmw/technology/valvetronic.htm

that valvetronic engines do not require a timing belt or chain so how does the cracksaft and pistons keep the correct timing with the inlet and exhaust valves on the head

this is all new to me i am used to working on way older cars an used to a timing belt or chain as i am picking up my 02 316ti compact next week trying to understand the way the engine works

any help or info would be helpful
 

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First introduced by BMW on the 316ti compact in 2001, Valvetronic has since been added to many of BMW's engines. The Valvetronic system is coupled with BMW's proven double-VANOS, to further enhance both power and efficiency accross the powerband. VANOS (Variable Nockenwellen Steuerung) is an automobile variable valve timing technology developed by BMW in close collaboration with Continental Teves. ...
Cylinder Head's with Valvetronic use an extra set of rocker arms, called intermediate arms, positioned between the valve stem and the camshaft. These intermediate arms are able to pivot on a central point, by means of an extra, electronicly actuated camshaft. This movement alone, without any movement of the intake camshaft, can open or close the intake valves. For the computer software/games company, see Valve Software A valve is a device that regulates the flow of fluids (either gases, fluidised solids, slurries or liquids) by opening, closing, or partially obstructing various passageways. ...

Because the intake valves now have the ability to move from fully closed to fully open positions, and everywhere in between, the primary means of engine load control is transferred from the throttle plate to the intake valvetrain. By eliminating the throttle plates "bottleneck" in the intake track, pumping losses are reduced and fuel economy is improved.

It is important to note however, that the throttle plate is not removed, but rather defaults to a fully open position once the engine is running. The throttle will partially close when the engine is first started, to created the initial vacuum needed for certain engine functions, such as emissions control. Once the engine reaches operating speed, a vacuum pump run of the passenger side exhaust camshaft (on the N62 V8 only) provides a vacuum source, much as a diesel engine would, and the throttle plate once again goes to the fully open position.

The throttle plate also doubles as an emergency backup, should the Valvetronic system fail. In this case, the engine would enter a "limp home" program engine speed would once again be controlled by the throttle plate.


http://www.nationmaster.com/encyclopedia/Valvetronic
 

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Discussion Starter · #3 ·
ah still not sure how this system works but will be reading up on this cheers

is that any chance mettalica lyrics in yer sig
 

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Discussion Starter · #5 ·
ahhhh is see does have a timing chain eh can safely say wont be doing a cylinder head on this engine am used to vauxhalls with 2 cams and a timing belt if the head ever goes on this think i will get a garage to do it will defo be buying a diagnostic tool to read the codes from the ecu though
 
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