How variable valve timing works

[pingu]

Explanation of why have it (0:00 to 0:50)
Explanation of how (0:50 to 1:25)
Double VANOS is continuous (1:26 to 1:34)
Single VANOS is 2 stage (1:34 to 1:43) [on at >5,000rpm and full throttle]
1:43 onwards is non-BMW specific, but of general interest.



The video was using camshaft degrees (360 per combustion cycle), I've used crankshaft degrees 720 per combustion cycle) to show the effect of VANOS -

Valve Timing Charts

(Flick between the two charts to see the VANOS advance)

This video shows how the VANOS operates. The camshaft has helical splines on the outside (which you can see) and the VANOS has helical gears on the inside. The VANOS is locked to the crankshaft in the single VANOS (as in the video) and is geared to the crankshaft (via the exhaust cam gear) on the double VANOS. As the gear (in his hand) moves in, the camshaft is advanced relative to the VANOS.

[Valle_fora]

Interesting! Thank you for posting.

[Brian H]

bloody clever stuff, thanks Pingu.