S54 Vanos Help

[oceansize]

Maybe next I’ll do rod bearings - but I’m starting to think with that just because a little copper is showing - it really doesn’t mean much. If you Google which metal is softer lead vs copper - it’s lead. Yes I understand if lead is worn away at one point - that means there is more critical.

But as we say in medicine - “is it clinically significant”? What is the thickness of that lead layer on a bearing? If just about every single person who has replaced rod bearings in their S54 has copper showing & l’m going to say < 1% of S54s throw a rod / rod knock - is that the root cause? BMW literally built ~ 100,000 of these S54 engines. Literally every person who changes their bearings & posts pics, almost regardless of mileage, has copper showing. And out of those “car forum people” that do get a rod knock - how many were tracked / abused cars? But yeah, I get it, better safe than sorry.

Rod bearings on an S54 are wear items and, as doctors are want to do, your moving outside your realm of experience and straight into anecdotal evidence land with a solid case of Dunning Krueger. Listen, there are guys who work on S54 engines by the hundreds (thousands?) on this forum. Rod bearings bother them enough that they will tell to change your rod bearings somewhere between 80 and 120k. I'm going with their outlook and these are solid forum citizens who don't need to drum up business by spreading fud.

[sapote]

This method does not require luck, gueswork, “pre-tensioning” of hub bolts

So you prefer not to pre-tension the hub 2 bolts? Why do you think BMW requires their worker to do this and wasting expensive labor on the production floor?

In your video at 12:59, you're talking about the important of torquing the hub bolts to spec because there is the "friction clutch" somewhere between the hub and the cam. I don't know there is a friction clutch in there for what purpose.

[Savageblunder]

So you prefer not to pre-tension the hub 2 bolts? Why do you think BMW requires their worker to do this and wasting expensive labor on the production floor?

In your video at 12:59, you're talking about the important of torquing the hub bolts to spec because there is the "friction clutch" somewhere between the hub and the cam. I don't know there is a friction clutch in there for what purpose.

I meant the cup washer system behind each hub that require a certain amount of resistance to be overcome for the vanos to move the hubs CW / CCW & splined shafts in & out once the 6 x 10mm bolts are tightened on each hub. I apologize for being vague.




The idea of video was to share the way I found to do it specifically on e85 Z4 M without the 2 above BMW specialty tools & be 100% sure the pistons are bottomed out where they should be, since you can’t put vanos/splined shafts in together on that car. I did it with 1 or 2 of the bolts completely tight on the hubs, which held the splined shafts in place & in turn the pushed the pistons back till they were past where the caps stopped them.

But honestly I realized in the process it doesn’t matter how you do it, as long as the bridge goes through the cams / the crank is at TDC & the vanos pistons are completely bottomed out. Thats all that matters for timing to be correct. You could argue if a “sweet spot” matters or not, but to me it seemed every few teeth was a sweet spot.

[sapote]

1. I meant the cup washer system behind each hub

2. The idea of video was to share the way I found to do it specifically on e85 Z4 M without the 2 above BMW specialty tools & be 100% sure the pistons are bottomed out where they should be, since you can’t put vanos/splined shafts in together on that car. I did it with 1 or 2 of the bolts completely tight on the hubs, which held the splined shafts in place & in turn the pushed the pistons back till they were past where the caps stopped them.
But honestly I realized in the process it doesn’t matter how you do it, as long as the bridge goes through the cams / the crank is at TDC & the vanos pistons are completely bottomed out. Thats all that matters for timing to be correct.
3. You could argue if a “sweet spot” matters or not, but to me it seemed every few teeth was a sweet spot.

1. I see. These cup springs are not for creating any kind of friction that the vanos needs, but they are for eliminating the axial plays between the hub and the cam to avoid oscillation during vanos closed-loop servo control. Unfortunately the springs also create the friction which is a negative side effect.
2. When bolting down the vanos or the piston caps to press the spline shafts into the hubs to turn them CCW to set the timing, without pre-tension the hub using 2 opposite bolts then there is backlash in the hub/spline shaft and resulted the timing is not precise as it should. Seeing the pin in the bridge and cam, and piston touching the cap are not enough if there is plays between the spline shaft and the hub at max retard position. If you don't have the hub pre-tension, then no guarantee that zero backlash in the hub/spline.
3. Sweet spot is useless and a waste of time as it doesn't gain anything.

[Savageblunder]

1. I see. These cup springs are not for creating any kind of friction that the vanos needs, but they are for eliminating the axial plays between the hub and the cam to avoid oscillation during vanos closed-loop servo control. Unfortunately the springs also create the friction which is a negative side effect.
2. When bolting down the vanos or the piston caps to press the spline shafts into the hubs to turn them CCW to set the timing, without pre-tension the hub using 2 opposite bolts then there is backlash in the hub/spline shaft and resulted the timing is not precise as it should. Seeing the pin in the bridge and cam, and piston touching the cap are not enough if there is plays between the spline shaft and the hub at max retard position. If you don't have the hub pre-tension, then no guarantee that zero backlash in the hub/spline.
3. Sweet spot is useless and a waste of time as it doesn't gain anything.

I’m missing how pre tightening the hub eliminates backlash that wouldn’t eventually be eliminated in the final tightening of 6 bolts in each hub? It seems BMW has revised the service procedure on this Vanos procedure multiple times I think there are an endless amount of ways to do it & the car drive fine.

I feel like the serviceability of the system is awful. Other manufactures you line X up with Y & your good.

[sapote]

I’m missing how pre tightening the hub eliminates backlash that wouldn’t eventually be eliminated in the final tightening of 6 bolts in each hub?

The whole point about setting the vanos timing is to have the following 5 requirements:
- crank and cams at TDC compression
- vanos pistons at max retarded position
- cam holes lined up with bridge pin
-splined shafts pushing hubs with certain amount of force to eliminate plays between them. This only can happen when splines are pushing the pre-tensioned hubs.
- chain has no slack on the pulling side (opposite of the tensioned side)

If the hubs are not pre-tensioned, there is no guarantee that the pistons are at their most retarded positions, and so the timing is not precise.

Yes, even when timing is not set precise, engine can run fine if the error is within the acceptable value, but why not do it as spec.

[Savageblunder]

The whole point about setting the vanos timing is to have the following 5 requirements:
- crank and cams at TDC compression
- vanos pistons at max retarded position
- cam holes lined up with bridge pin
-splined shafts pushing hubs with certain amount of force to eliminate plays between them. This only can happen when splines are pushing the pre-tensioned hubs.
- chain has no slack on the pulling side (opposite of the tensioned side)

If the hubs are not pre-tensioned, there is no guarantee that the pistons are at their most retarded positions, and so the timing is not precise.

Yes, even when timing is not set precise, engine can run fine if the error is within the acceptable value, but why not do it as spec.

That’s why it made sense for me to install vanos with piston caps off, so I can 100% see & measure where they are in the bore. Doing it that way you can also manipulate when / if they go back in their bore by loosening / tightening the 6 hub bolts as the vanos gets slowly bolted towards the head. Anyway, worked perfect for me & car runs great.