S54 Vanos post Beisan/DV Rebuild Timing Issue

[Cubieman]

So when you say bias the cams. I should put the engine at TDC but not lock it. Then dial in cam to line with the bridge (tiny lift on tool on intake side when I tighten up) and this is technically biased?

Then rotate a few times and see if it all lines up with bridge when locked at TDC?

Thanks

No, if you want to bias a cam you would lock the crank at TDC1.

Let's says you set your cams up so the bridge sits perfectly flat on the head with the crank locked at TDC1, you torque your hub bolts to spec but after you turn the engine over 4 times and lock at TDC1 again now you find you have a gap between the bridge and head on the intake side of head when checking the intake cam.

In the case of this hypothetical scenario you would re-time but instead of setting up the intake cam so the bridge sits flat you need to slightly advance the intake cam, this means rotating slightly Clockwise as viewed from front of the vehicle.

If both of your cams are off by about the same it would be easier to bias the crank, you either bias the crank ~1-2mm CW or CCW depending on if your cams end up slightly advanced or retarded when you check timing with the bridge.

[Arinb12]

So when you say bias the cams. I should put the engine at TDC but not lock it. Then dial in cam to line with the bridge (tiny lift on tool on intake side when I tighten up) and this is technically biased?

Then rotate a few times and see if it all lines up with bridge when locked at TDC?

Thanks

[Cubieman]

How much do you bias and how? I have the same issue and even the torque marks and guide in post 3 give me the same issue. Do I bias the crank and then time up?

You can bias the crank or the cams, the cams might be better as you can dail in each individually whereas with biasing the crank you of course affect both cams.

You find out how much you are off, bias the cam(s) that are off (or bias the crank instead), torque things down and hopefully when you spin the engine around a few times your timing bridge sits flush.

As to how much biasing, just measure or eyeball how far your bridge is off the head and compensate that by biasing cam(s) or crank.

As long as your bridge is less than 1mm off the head your fine, I tired to get as flush as possible though.

[Arinb12]

How much do you bias and how? I have the same issue and even the torque marks and guide in post 3 give me the same issue. Do I bias the crank and then time up?

[sapote]

For those that have the timing bridge that off the head on the intake side after complete the VANOS timing procedure, I believe this is mostly due to the chain slack. For whatever the reason BMW instruction doesn’t ask to use a solid chain tension as it is required when doing the timing on non-M cars. As soon as the hubs bolts were released, the sprockets are free to turn and causing chain slack on the pulling side (RH side front view) which leads to the timing small error.

We have 2 choices to correct this: install a hard chain tensioner tool (I used a socket instead of the stock spring loaded piston), or offset the crank pulley 2mm CCW from TDC.
For those that have the timing bridge that off the head on the intake side after complete the VANOS timing procedure, I believe this is mostly due to the chain slack. For whatever the reason BMW instruction doesn’t ask to use a solid chain tension as it is required when doing the timing on non-M cars. As soon as the hubs bolts were released, the sprockets are free to turn and causing chain slack on the pulling side (RH side front view) which leads to the timing small error.

We have 2 choices to correct this: install a hard chain tensioner tool (I used a socket instead of the stock spring loaded piston), or offset the crank pulley 2mm CCW from TDC.

[sapote]

ALL hub bolts - the 6 of them. I am sorry this is not clear, this implies the hubs are already on the sprockets, with all bolts in place but finger tight. this can be done with, or without the spline inserted, does not matter as you need to loosen all of them again to start the assembly, this is just to have visual marks for the torque settings. this works, it was tested, and you can repeatedly reach 14NM and have the marks aligned as long as you don't pull the screws out completely and inserted in another location

as for your comment above, I am sorry but you are not correct. and no, you don't have to bias the crank to achieve timing. if the preload process is done correctly it wont move. there are physical reasons for this which I bullet point bellow

• preload by tightening one bolt at a time skews the hub, which makes the spline to bin and as a result is dragged in separating the piston from the cap
• if preload is done by tightening side by side by small amounts (1/4 of a turn on this bolt is just 0.25mm of displacement), this allows the hub to rotate around the spline as it is being tighten, this wont drag the spline in

there are other potential ways around this, like torque the hubs with the splines in but out enough that they will remained bottomed out as the VNAOS unit is placed. the torque of the VANOS bolts will force it in place making the hubs to spin CCW. Not that I would do this, I told my friend not to try this even when he had been told this worked for his mechanic friend 100's of times. but hey, there are several ways to skin a cat, you pick what you feel more comfortable with.

BTW, we tried the bias approach, and the two times we did it we were off, at which point it was just more effective to do what we did (what I wrote). this sequence allowed the engine to be on time with both pins sliding easily with the bridge flat on the head.

1) Add the final torque mark on the bolts is a great idea.
2) So after pretension the hub with the 2 bolts (across from each other), the hub could move away from the cam/sprocket by 0.25mm max. This means during the final torqueing down the hub, it only can move rearward 0.25mm max and the potential of pulling the piston rearward no more than 0.25mm away from the VANOS cap. The hub cannot pull the piston more than the distance the hub actually moved, 0.25mm. So the idea that when the 2 hub bolts are not evenly torqued down -- total only 1/4 turns -- that cause the hub to pull the piston more than 0.25mm is not right. Say how could the piston moves 0.50mm off the cap if the hub only moved 0.25mm?
3) Here is what cause the final small error: the hub moved 0.25mm at the final torqueing step + the chain slack when the original hubs bolts were loosen. The amount of chain slack depends on how tight the chain tensioner is with no oil pressure. Some has more than the others depending on the oil leaking condition. The M3 vanos instruction doesn't require a special tensioner vs. the non-M cars require this special tensioner to keep the chain tight during the whole process after setting the crank and cams at timing positions. So to compensate for the error, the crank needs to be offset a few millimeter CCW from TDC.

[maupineda]

* "tighten the hubs with a torque wrench to 14NM, and add what I call torque marks"
This is unclear instruction, as the hub has no threads to be tighten.And if using bolts then how many bolts? Don't assume people will only use 2 bolts.

* "what happens is that if preload is not applied evenly, as you tighten the hub, it drags the piston into the hub effectively creating space between the piston and the VANOS unit cap"
When the hub is bolting down, for sure it will pull the piston the same amount of movement by the spline shaft. You can't expect the spline shaft somehow be able to slip through the hub and not being pulled along (it might turn instead of being pulled along, but since pulling the piston is a very light load and so I bet the spline shaft not rotate but being pulled along), no matter how EVENTLY you torque down the 2 bolts. This is the reason why one should bias the crank pulley a few mm CCW to compensate for this "pistons pulling syndrome" which causes the final timing a little retarded.

ALL hub bolts - the 6 of them. I am sorry this is not clear, this implies the hubs are already on the sprockets, with all bolts in place but finger tight. this can be done with, or without the spline inserted, does not matter as you need to loosen all of them again to start the assembly, this is just to have visual marks for the torque settings. this works, it was tested, and you can repeatedly reach 14NM and have the marks aligned as long as you don't pull the screws out completely and inserted in another location

as for your comment above, I am sorry but you are not correct. and no, you don't have to bias the crank to achieve timing. if the preload process is done correctly it wont move. there are physical reasons for this which I bullet point bellow

• preload by tightening one bolt at a time skews the hub, which makes the spline to bin and as a result is dragged in separating the piston from the cap
• if preload is done by tightening side by side by small amounts (1/4 of a turn on this bolt is just 0.25mm of displacement), this allows the hub to rotate around the spline as it is being tighten, this wont drag the spline in

there are other potential ways around this, like torque the hubs with the splines in but out enough that they will remained bottomed out as the VNAOS unit is placed. the torque of the VANOS bolts will force it in place making the hubs to spin CCW. Not that I would do this, I told my friend not to try this even when he had been told this worked for his mechanic friend 100's of times. but hey, there are several ways to skin a cat, you pick what you feel more comfortable with.

BTW, we tried the bias approach, and the two times we did it we were off, at which point it was just more effective to do what we did (what I wrote). this sequence allowed the engine to be on time with both pins sliding easily with the bridge flat on the head.

[Cubieman]

You can train an ant and place it inside then bolt down the cap and ask the ant to see if there is any gaps between the piston end and the cap, as this is the only way.
Or, this is even better: ask the ant to stand on the end of the piston, then bolt down the cap to spec, then remove the cap and see if our dear ant was flatted down to less than paper thin.

Ha, now that's what I need this in my toolbox. I just figured that once the piston reached that tapered edge that was it. But as you say not exact, I will post measurement "C" if/when I do it.

[sapote]

You are correct, I don't have a point of reference except visual from a YouTube video/my assement of what looks to be the "end point" for the pistons. I didn't perform and sort of measurement. Would be nice to know the distance measurement if someone has it.

A video or picture cannot convey 1mm or 2mm difference. A sure way is to measure the distance "C" from the cap base to the tip of the inside circular riser (it's a broken circle in order for the oil to flow through), then measure the end of piston to the vanos face and this dimension should be equal to C.

[Cubieman]

You meant as far forward as possible?
Hmm, how do you know it was as far as it can be? You have no reference to know this, or it might be 2mm short?

I meant they were as are far back into the vanos as possible. And you are correct in that I don't know for a fact that they are into the vanos as far as possible.

I watched a video linked in the Vanos Mega Thread in which the gentleman removed the caps demonstrating the correct postion of the vanos pistons and mine were dead even with the tapered portion of the cylinder shown in the photos.

If you look inside the caps there is a small circular protrusion that I *think* acts as the stop point for the pistons. So it would appear that visually my pistons were in the vanos as far as possible.

You are correct, I don't have a point of reference except visual from a YouTube video/my assement of what looks to be the "end point" for the pistons. I didn't perform and sort of measurement. Would be nice to know the distance measurement if someone has it.

[sapote]

After I was all done I removed the vanos "caps" just to make me feel better, it would appear that the pistons were as far back as possible.

You meant as far forward as possible?
Hmm, how do you know it was as far as it can be? You have no reference to know this, or it might be 2mm short? You can train an ant and place it inside then bolt down the cap and ask the ant to see if there is any gaps between the piston end and the cap, as this is the only way.
Or, this is even better: ask the ant to stand on the end of the piston, then bolt down the cap to spec, then remove the cap and see if our dear ant was flatted down to less than paper thin.

[Cubieman]

Glad to hear I am not alone. I spoke with Raj about this... He basically said this just happens to some engines, no one knows why. He said that what he has heard people do is that they do what I did and bias it. Hasn't heard of any ill effects. I have turned the engine over 20+ times doing valve adjustments, and timing is still spot on so I am satisfied.

Awesome, sounds like your good to go then! I was so very nervous, "I am timing an S54 engine and it's not going according to instructions!"
I was shaking as a turned the key the first time, no shit.
I really thought I might introduce the pistons to the valves. The forum members were quite helpful/patient, Raj told me the same thing in regards to why the biasing must be done sometimes, kind of unknown. I'm sure there's reasons, there must be, it's just probably so many things it could be it wasn't worth speculation.

[sapote]

- before putting the VANOS unit on, tighten the hubs with a torque wrench to 14NM, and add what I call torque marks... add two marks per bolt so you have two reference points, this will allow to torque the hubs much closer to the actual spec than go by feel

what happens is that if preload is not applied evenly, as you tighten the hub, it drags the piston into the hub effectively creating space between the piston and the VANOS unit cap, and it is KEY (aka A MUST) that pistons remained bottomed out into the VANOS unit for timing to be maintained, if they are pulled into the hub during preload and they no longer are bottomed out, as you spin the engine, the cams will not start rotating along with the engine until they are bottomed out again, and this is what throws your timing off, it is very minor, but enough to not let the pin on the bridge to go in fully.

* "tighten the hubs with a torque wrench to 14NM, and add what I call torque marks"
This is unclear instruction, as the hub has no threads to be tighten.And if using bolts then how many bolts? Don't assume people will only use 2 bolts.

* "what happens is that if preload is not applied evenly, as you tighten the hub, it drags the piston into the hub effectively creating space between the piston and the VANOS unit cap"
When the hub is bolting down, for sure it will pull the piston the same amount of movement by the spline shaft. You can't expect the spline shaft somehow be able to slip through the hub and not being pulled along (it might turn instead of being pulled along, but since pulling the piston is a very light load and so I bet the spline shaft not rotate but being pulled along), no matter how EVENTLY you torque down the 2 bolts. This is the reason why one should bias the crank pulley a few mm CCW to compensate for this "pistons pulling syndrome" which causes the final timing a little retarded.

[Joshb556]

Glad to hear I am not alone. I spoke with Raj about this... He basically said this just happens to some engines, no one knows why. He said that what he has heard people do is that they do what I did and bias it. Hasn't heard of any ill effects. I have turned the engine over 20+ times doing valve adjustments, and timing is still spot on so I am satisfied.

[maupineda]

they will be fine if you torque to spec, don't worry, just use a torque wrench since aluminum does not take much to be screwed over.