Subject: Here's a cleaner 'let me step in here...' Author: ZetaTre : member since May, 2009 : 32 posts Posted on: 2009-05-15 18:05:47

In the double-VANOS systems there is not a single chances of affecting the timing in any possible way (hopefully that’s not too redundant… eheheh): the helical gear remains between the sprocket and the cams and will not come loose once the VANOS is removed. The only way to remove the helical gear is if you turn the cams. But even if you do it, there is only one possible way to reinsert the helical gear since it's keyed.

You can see clearly the key from this tool used for the cam aligning tool:



You can see how one of the valley in the outer and inner splines is filled: this is to match a missing spline in the sprockets and cams.

Bottom line: the only way to affect timing on double vanos car is by releasing the bolt on the sprocket. This is not part of the procedure so timing is left untouched and no cam locking tool is required.



The single-VANOS (such as what you have in you 528) is not so "user friendly" since you 1) can't remove the VANOS without removing the helical gear and 2) the helical gear is not keyed.

This is where the cam locking too comes in place. I'm not sure how it is in the UK, but here on the other side of the pond people get scared cuz they think small-block Chevy and timing light. THIS IS NOT HOW TIMING IS DONE ON BMW (or other modern cars, including GMs): timing is embedded in the cam's design.

Quick note: "cam timing" ultimately describes the position of the cams relative to the crank. This means both cams and crank are involved in the timing process.

You first lock the crank so that cylinder #1 is at TDC. At this point the cams are positioned in such a way that the key in the rear are perpendicular to the head surface. You then use the blocks to lock the cams in such position (the pin that goes in the chain tensioner is to deactivate it). At this point cams are locked & crank is locked which means timing is locked.

The reason to remove the exhaust sprocket bolts is because the helical gear needs to turn in order to be removed. Since the cams and crank are locked you can’t just turn the cams (as in the double VANOS), but you need to release the bolts on the sprocket in order to turn it.
By turning the exhaust sprocket, the intake sprocket tries to turn; the intake cam is locked so the helical gear pushes out. When you mount the VANOS you turn the sprocket the other way; the intake cam is still locked the helical gear get "sucked" in.

If you think about it you'll realize this is really just what the VANOS does, just in reverse: when the VANOS piston pushes in the helical gear makes the cam turn relative to the sprocket. When you remove the VANOS you turn the sprocket relative the cam and the helical gear gets pushed out.

Hopefully this makes more sense...

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1998 Z3 1.9 (my baby)
2003 Z4 2.5i (my babe's baby)

• Questions from UK - poppell 2009-01-29 06:10:07 (610 views)
  • Re: Questions from UK - bananaman 2009-05-12 05:44:57 (477 views)
    • Re: Questions from UK - Rajaie 2009-05-18 00:26:03 (459 views)
    • Here's a cleaner 'let me step in here...' (pic) - ZetaTre 2009-05-15 18:05:47 (548 views)
    • Let me step in here... - ZetaTre 2009-05-15 17:45:59 (423 views)
      • PS: what heppend to my coding?? - ZetaTre 2009-05-15 17:47:45 (462 views)
        • Re: PS: what heppend to my coding?? - bananaman 2009-05-20 09:54:48 (403 views)
          • Glad I was of some help!!!! (nt) - ZetaTre 2009-05-21 13:22:58 (390 views)
        • Let's see if it works now... (pic) - ZetaTre 2009-05-15 17:52:29 (478 views)
  • Re: Questions from UK - Rajaie 2009-01-30 00:34:03 (549 views)