Originally posted by Savageblunder
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Originally posted by Savageblunder View PostThis method does not require luck, gueswork, “pre-tensioning” of hub bolts
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.
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Originally posted by sapote View Post
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.
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.
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Originally posted by Savageblunder View Post
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.
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.
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Originally posted by sapote View Post
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 feel like the serviceability of the system is awful. Other manufactures you line X up with Y & your good.
Last edited by Savageblunder; 10-20-2024, 10:59 AM.
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Originally posted by Savageblunder View PostI’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?
- 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.
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Originally posted by sapote View Post
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.
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