Engine won't time post Vanos install

[ATB88]

Yeah, so, the problem that you're experiencing is actually pretty normal from that I understand. There will always be this little bit of "timing drift" in the first few times you turn the engine over after initially setting the timing (from normal chain slack and or other slack in the system). If I had to guess, if you just set the timing as you have been, got it perfect with the alignment bridge, and instead of turning it over three times to re-check, you just buttoned the car up and turned it on, you'd be fine. You'd probably find that the timing isn't 100% bang on perfect, but is within allowable tolerances (few degrees). And my understanding is that this is what a lot of people do. It's actually what I ended up doing first time I did VANOS, and my timing as determined in DIS actually ended up being quite close to perfect. (EXPERTS: am I wrong on this? is this bad advice??)

I, like you, am a little bothered by this, and when robgill helped me do my last VANOS last time, he taught me the same trick that Sapote is suggesting: if you know that the timing is going to drift a little bit the first few revolutions of the engine, try and compensate for that in how you initially set the timing, so that it will drift into "perfect spec". It's a little frustrating and demands a LOT of trial and error, but is doable.

[Cubieman]

Yeah, so, the problem that you're experiencing is actually pretty normal from that I understand. There will always be this little bit of "timing drift" in the first few times you turn the engine over after initially setting the timing (from normal chain slack and or other slack in the system). If I had to guess, if you just set the timing as you have been, got it perfect with the alignment bridge, and instead of turning it over three times to re-check, you just buttoned the car up and turned it on, you'd be fine. You'd probably find that the timing isn't 100% bang on perfect, but is within allowable tolerances (few degrees). And my understanding is that this is what a lot of people do. It's actually what I ended up doing first time I did VANOS, and my timing as determined in DIS actually ended up being quite close to perfect. (EXPERTS: am I wrong on this? is this bad advice??)

I, like you, am a little bothered by this, and when robgill helped me do my last VANOS last time, he taught me the same trick that Sapote is suggesting: if you know that the timing is going to drift a little bit the first few revolutions of the engine, try and compensate for that in how you initially set the timing, so that it will drift into "perfect spec". It's a little frustrating and demands a LOT of trial and error, but is doable.

Maybe part of my issue is that I am only turning the engine over 1 time in order to check timing. However if its drifting out of timing after only 1 turn of the crank im sure it will still be out of time after 5 or 50 turns of the crank.
The cams are just "behind" the crank in that if I turn the crank just a tiny a bit more past TDC the timing tool slots right in so I'll try timing the cams a bit "foward" of the crank to see what happens.
I am just frustrated that its not going according to the instructions kind of a thing, thats what I get for screwing around with things that I don't have a full understanding of. I just wish I knew why the slack in the chain is enough to cause this issue, in all the vanos info I have read I have never seen a warning to look out for this issue.

[ATB88]

Wait help me understand something I'm a little unclear on -- are you following the part of the setting/checking timing portion of the Beisan procedure to the letter (no extra rotations of the engine or extra checks) and failing to verify that the engine is in time? Or are you turning over the engine and checking timing additional times (beyond what you would when following the Beisan procedure to the letter) just to see if it drifts?

If the former, then I agree that you should be concerned. If the latter, then the problem is that you're demanding more accuracy and precision of this procedure than it is designed for -- which is okay, but is going to lead to some tedious and frustrating time tinkering that isn't strictly necessary in order to have done this job properly.

[Cubieman]

Wait help me understand something I'm a little unclear on -- are you following the part of the setting/checking timing portion of the Beisan procedure to the letter (no extra rotations of the engine or extra checks) and failing to verify that the engine is in time? Or are you turning over the engine and checking timing additional times (beyond what you would following the Beisan procedure to the letter) just to see if it drifts?

If the former, then I agree that you should be concerned. If the latter, then the problem is that you're demanding more accuracy and precision of this procedure than it is designed for -- which is okay, but is going to lead to some tedious and frustrating time tinkering that isn't strictly necessary in order to have done this job properly.

I am following the beisan procedure in that once you turn the crank to TDC lobes 45° and torque the top three remaining hub bolts you check timing after retarding the cams.
Although the 3 attempts I have followed the Beisan procedure I accidentally went too far with the crank CW so the crank locking pin would not go in.
So instead of turning the crank CCW I just went around again until I could insert the crank pin. This may have allowed for the drift.

Last night I tried pre-tensioning the left/right hub bolts and tightened all other hub bolts I could get a wrench on then I completely removed the vanos leaving the splined shafts in the hubs. I was then able to put a torque wrench on each and every hub bolt. I put the vanos back on and turned the crank to TDC lobes 45° to check timing and the timing issue was identical.

[Cubieman]

I'm almost positive the slack in my timing chain is the issue. If I get all the hub bolts torqued down and rotate to TDC lobes 45° my bridge will sit flat on the Intake cam and more or less flat on the Exhaust cam, its only when I retard the cams that I have an issue with the bridge.
I can move the cams back/forth enough with the vanos installed, hubs bolts fully tightened and crank TDC lobes 45° to make a notable difference in the way the timing bridge sits. I think there is too much slack in the chain, I can't imagine this enigne running 8,000RPM with any slack.

[maupineda]

it sounds you are overdoing it. I found a similar situation, I wanted the pins to slide in like butter as they did when setting all up, then after the full first turn, the pin just will not go in as easy, and the exhaust cam would actually require me to spin the engine CCW for that to happen, which I know we should not do. So I just made sure I was following the process and put her back together and stop chasing perfection, despite that caveat my timing is spot on, okay, not zero, but is a mere 2.4 deg "off" on the exhaust side and intake is dead on, but the ECU takes care of that small variance.



For reference, below is what I had before doing the VANOS, it wasn't "perfect" either, on the image below the engine was not running, so you see there is not variation from what the ECU requested, vs what it was getting, on the image above, engine was running, and with the adaptations, you can see that the ECU gets pretty much what she wants.




Don't lose sleep on this, you may actually break something trying for perfection, and then you will hate yourself (been there!!)

[Icecream]

Exactly, 1mm (approx.) gap on the intake side when checking the exhaust cam and the intake is less than that but still off. If I turn the crank just slightly CW the bridge sits flats, but of course then the crank pin won't go in so it's not at TDC.

That was what mine did. It was fine, I think I cheated it a little so the gap was very small. If I find the bmw doc it states this as ok as well ( I think it said .3mm) If everything else is buttoned up the drift wont get worse with more rotations. If there is no interference when turning over and everythibg else is followed on the instructions, if it we're me, I would button it back up and be done. I know the feeling of it not being perfect, I went through it myself, but mine timed about as perfect as you can get it via DIS. I feel like you risk more damaged bolting and un bolting, tightening and loosening (remember the cam pin incident) but you can try cheating the timing and see if that works.

[Cubieman]

That was what mine did. It was fine, I think I cheated it a little so the gap was very small. If I find the bmw doc it states this as ok as well ( I think it said .3mm) If everything else is buttoned up the drift wont get worse with more rotations. If there is no interference when turning over and everythibg else is followed on the instructions, if it we're me, I would button it back up and be done. I know the feeling of it not being perfect, I went through it myself, but mine timed about as perfect as you can get it via DIS. I feel like you risk more damaged bolting and un bolting, tightening and loosening (remember the cam pin incident) but you can try cheating the timing and see if that works.

I hear you on potentially doing more harm than good by repeatedly taking things apart. I have discovered that I can get the bridge to sit flat on the head TDC if I don't fully retard the cams. The cams don't retard much after turning the crank to TDC, but its enough to where its makes a difference on wether or not the bridge sits flat.

My main concern is timing chain slack, I didn't note how much there was before taking things apart so I don't have a reference point.

[sapote]

I just wish I knew why the slack in the chain is enough to cause this issue, in all the vanos info I have read I have never seen a warning to look out for this issue.

Imagine after the cams were timed to the bridge and the crank was at TDC, but there was a little chain slack. So after all of the hard work of pretension the hub and bolting down the vanos, hub bolts, it is time to check the final timing. Well, because of the little slack on the chain pulling side, you turned the crank CW a little pass TDC and the chain slack is gone but the cams do not turn, and so the cams are still timed perfect with bridge but the crank is overshoot the TDC, exactly as your issue.

[sapote]

I think there is too much slack in the chain, I can't imagine this enigne running 8,000RPM with any slack.

Yes, your issue of not get a perfect timing (although it will pass the test) is due to chain slack on the pulling side. At 8000 rpm or any rpm the pressurized oil increase the chain tensioner to eliminate any slack. However during doing this work with engine off, you need to ensure there is no slack on pulling side by turning crank very slow CW when set it to TDC, as a little overshoot will lead to slack as the tensioner doesn't have enough tension with zero oil pressure.

[sapote]

My main concern is timing chain slack, I didn't note how much there was before taking things apart so I don't have a reference point.

I think you're concerned about chain stretched longer due to old part, but even for an old chain that stretched 3mm total longer, this does not cause timing error as long as when turning crack cw to set at TDC and having the cams timed to bridge with zero chain slack on pulling side from crank to cam sprocket.

Let's see how did you have little chain slack. After setting the crank at TDC compression cycle, how did you turn the cams to time with bridge?
1) if you turn the EX cam CCW to time by the pin, then you turned the IN cam CCW to time it, this could cause chain slack between the 2 cams. To avoid this, always turn IN CCW to time it first, then turn EX cam to time it. As the EX cam being turned CCW, it wanted to turn the EX sprocket along and take out any slack in between the cams. Never turn the cams CW -- even just a little -- during inserting the pin, as this will cause chain slack between cam sprocket and crank.

[Cubieman]

I think you're concerned about chain stretched longer due to old part, but even for an old chain that stretched 3mm total longer, this does not cause timing error as long as when turning crack cw to set at TDC and having the cams timed to bridge with zero chain slack on pulling side from crank to cam sprocket.

Let's see how did you have little chain slack. After setting the crank at TDC compression cycle, how did you turn the cams to time with bridge?
1) if you turn the EX cam CCW to time by the pin, then you turned the IN cam CCW to time it, this could cause chain slack between the 2 cams. To avoid this, always turn IN CCW to time it first, then turn EX cam to time it. As the EX cam being turned CCW, it wanted to turn the EX sprocket along and take out any slack in between the cams. Never turn the cams CW -- even just a little -- during inserting the pin, as this will cause chain slack between cam sprocket and crank.

What exactly do you mean by pulling side? I feel a bit of slack in the chain right between the sprockets. I have been moving the crank slowly/evenly trying to hold it in place while the air escapes during compression rather than letting it spring back a little as it goes along.

You said to never turn the cams CW. During timing (when all hubs bolts are loose) I have been bumping the cams back and forth (CW&CCW) to find the perfect spot so the timing pin drops right in.

When my timing ends up wrong (both cams too far CCW, bridge gap on intake side) I have been only adjusting for exhaust by loosening all exhaust hubs bolts and trying again.
Maybe I should try to loosen both cams at once and start with the intake side to re-time it and then move to exhaust.

During the removal of my timing chain tensioner I dumped a bunch of the oil out of it as TIS said to compression it 2 times before re-installing it, I wonder I I took it out and poured oil in it if that might help at all in taking slack from the chain. Probably not as the oil is forced in at high pressure which I can't do by simply pouring it in.

I am lost and don't feel like starting the car until I can at least get both cams within. 5mm when using the timing tool. I'll likely make a video of my issues and post it here. For now I am going to try to adjust the hubs with the vanos still attached. I am running out of things to try. I am not striving for perfect, but I just want the timing tool to be within .5mm off the head and at this point I am unable to achieve that. I haven't tried "cheating" the timing yet.

Thanks so much for yours and everyone's help.

[Cubieman]

Video of chain slack.

https://youtube.com/shorts/XacCjaD47Ig

[sapote]

In the video the chain is tight so it’s not a problem.
No chain slack on pulling side: viewing from front the crank pulled the cam sprockets CW, hence the pulling side is on the right, not chain tensioner side.

Do this if you want perfect timing, starting from beginning for a normal working car:
1) Turn crank cw to TDC but stop at about 2mm before TDC mark. This will cheat and give the cams little advanced timing to correct your issue. Don’t need to lock crank with pin.
2) do the remaining steps as you did before with cams timed by the pin and bridge sit FLAT on the head on both sides.

3) Turn crank 2 or 4 turns and check the final timing should be perfect.

[sapote]

Don’t worry about damaging the engine as long as you turned the crank cw 2 or 4 turns to TDC and the cams are timed with pin and bridge sits flat or within 1mm on head. All hub bolts are torqued to spec so nothing moving to cause damage.