Vanos splined shafts "sweet spot"

[PipeUy]

So I was watching some S54 related videos and I came about this one. The guy in the video talks about a "sweet spot" where the amount of movement achieved by the vanos splined shafts is the maximum and talks about a theoretical power gain and/or a broader power band. Does this make any sense or is it just a myth?

[eacmen]

So I was watching some S54 related videos and I came about this one. The guy in the video talks about a "sweet spot" where the amount of movement achieved by the vanos splined shafts is the maximum and talks about a theoretical power gain and/or a broader power band. Does this make any sense or is it just a myth?

No measurable difference in power have been demonstrated. BMW TIS makes no mention of this sweet spot. That being side, installing it as described won't hurt anything. When I did my VANOS I chose to find it and use it since it didn't hurt and was basically no extra effort.

[Obioban]

It doesn’t hurt, but it doesn’t benefit either.

[PipeUy]

No measurable difference in power have been demonstrated. BMW TIS makes no mention of this sweet spot. That being side, installing it as described won't hurt anything. When I did my VANOS I chose to find it and use it since it didn't hurt and was basically no extra effort.

It doesn’t hurt, but it doesn’t benefit either.

Alright, that's what I thought. I'll do it since it's no extra effort and for the peace of mind that if something could be gained it was done.

[mrgizmo04]

I'd watch/follow fatboys videos with a grain of salt (I'd only recommend following Beisan/TIS, and no, unfortunately they dont have their instructions in video form ).

There are a lot of steps skipped or described incorrectly in their series, although they do have a lot of useful parts/information to visually present the steps. On the old forum they had a thread for their videos and asked for feedback. I provided a lot. Not all of it made it into the videos (it's hard to re-shoot and re-edit some steps of a process when the car has already been put together and running).

Short answer to your q, as mentioned, just use the first tooth while rotating the hub, sweet tooth or not. There is no power to be gained from a "sweet tooth" lol.

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[PipeUy]

I'd watch/follow fatboys videos with a grain of salt (I'd only recommend following Beisan/TIS, and no, unfortunately they dont have their instructions in video form ).

There are a lot of steps skipped or described incorrectly in their series, although they do have a lot of useful parts/information to visually present the steps. On the old forum they had a thread for their videos and asked for feedback. I provided a lot. Not all of it made it into the videos (it's hard to re-shoot and re-edit some steps of a process when the car has already been put together and running).

Short answer to your q, as mentioned, just use the first tooth while rotating the hub, sweet tooth or not. There is no power to be gained from a "sweet tooth" lol.

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Thanks for the input, my plan is to follow the Beisan procedures since their procedures are extremely well explained and it's what everyone recommends. I already bought everything I need for the vanos job and I should be able to do it in a couple of weeks, was curious about that "sweet spot" haha.

[eacmen]

I'd watch/follow fatboys videos with a grain of salt (I'd only recommend following Beisan/TIS, and no, unfortunately they dont have their instructions in video form ).

There are a lot of steps skipped or described incorrectly in their series, although they do have a lot of useful parts/information to visually present the steps. On the old forum they had a thread for their videos and asked for feedback. I provided a lot. Not all of it made it into the videos (it's hard to re-shoot and re-edit some steps of a process when the car has already been put together and running).

Short answer to your q, as mentioned, just use the first tooth while rotating the hub, sweet tooth or not. There is no power to be gained from a "sweet tooth" lol.

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Concur. I also use beisan procedures as truth with videos as a visual reference.


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[beefaroni]

I found the sweet tooth and now I take Veyrons to Gapplebee's

The main thing it really does is satisfies your automotive OCD.

Feelsgoodman

[Cubieman]

I found the sweet tooth and now I take Veyrons to Gapplebee's

The main thing it really does is satisfies your automotive OCD.

Feelsgoodman

Lol

[JamesSJ1]

My 2 cents...probably all it's worth. I just did a vanos anti-rattle rebuild, and added-on the sweet spot check while I was at it.

As you insert the spline shaft, you'll find the alignment of the center with the outer splines can be as much as 99% turned relative to the hub, which means it will require nearly a full tooth of counter-clockwise rotation before it will insert to the hub. If you keep pulling it out and inserting the center to the next tooth, you'll see a progressive difference in the outer/hub alignment. Eventually, you'll get to the point where it's literally perfect or just a hair off on the clockwise side, where virtually no rotation is required.

Does it really matter? Probably not. I've screwed up my timing enough despite my efforts, and learned that the system will still pass the vanos test at a maximum of 6 degrees of adaptation. Given that, there is probably a large range of error that has no impact on performance, and nearly one tooth of rotation, as long as it inserts into the first tooth possible as instructed, won't cause any issues.

EDIT: My adaptation result was 0.2 degrees and 0.4 degrees, which is darn near perfect compared to what we've discussed in previous M3F threads. My OCD is in its happy place.

[eacmen]

My 2 cents...probably all it's worth. I just did a vanos anti-rattle rebuild, and added-on the sweet spot check while I was at it.

As you insert the spline shaft, you'll find the alignment of the center with the outer splines can be as much as 99% turned relative to the hub, which means it will require nearly a full tooth of counter-clockwise rotation before it will insert to the hub. If you keep pulling it out and inserting the center to the next tooth, you'll see a progressive difference in the outer/hub alignment. Eventually, you'll get to the point where it's literally perfect or just a hair off on the clockwise side, where virtually no rotation is required.

Does it really matter? Probably not. I've screwed up my timing enough despite my efforts, and learned that the system will still pass the vanos test at a maximum of 6 degrees of adaptation. Given that, there is probably a large range of error that has no impact on performance, and nearly one tooth of rotation, as long as it inserts into the first tooth possible as instructed, won't cause any issues.

EDIT: My adaptation result was 0.2 degrees and 0.4 degrees, which is darn near perfect compared to what we've discussed in previous M3F threads. My OCD is in its happy place.

How did you get the vanos adaptation values?


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[Icecream]

So I was watching some S54 related videos and I came about this one. The guy in the video talks about a "sweet spot" where the amount of movement achieved by the vanos splined shafts is the maximum and talks about a theoretical power gain and/or a broader power band. Does this make any sense or is it just a myth?

sent from my mackintosh

[heinzboehmer]

How did you get the vanos adaptation values?


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Pretty sure INPA can do it. Or https://www.ecuworx.co.uk/2020/05/03...m3-by-ecuworx/

[mrgizmo04]

INPA is one of the few tools that can read and reset vanos adaptations. Resetting adaptations normally does not reset vanos adaptations, those are handled separately. That said, when I reset adaptations via INPA, vanos adaptations also reset. On the Foxwell/Schwaben tool for example, they are 2 separate menus.

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[sapote]

"sweet spot" is a particular position of the spline shaft that best matching its splines to the hub splines. Does the system need it? No, because the normal operating range of the variable cam timing is much less than this "sweet spot" range. IOW, the longer traveling range of the 'sweet' spline shaft is not needed during normal operation of the engine by design (controlled by the DME).