[F87source]

Originally Posted by Megator

A bolt under tension does not just vibrate loose. If loosening under vibration was an issue then there are like 5 cheap and fast fixes BMW could have implemented which would all cost much less than the warranties on S55 engines.

The bolt is like a spring right, for it to vibrate loose the pretension on it must be reduced to the point where the mechanical loads on it can cause it to slip. This can happen for example in very hot conditions where a bolt expands more than the bits its holding together.

Or from vibration forces which might "pry" the joint open allowing the bolt to somewhat back off. I dont really see how this plays a role on the S55 unless the crank is literaly slaming back and forwards in the engine like an old diesel.

Just found this great explanation of the crank hub and CBC from TPS performance, its in German but allows auto generated translated captions.

I am not sure about what all CBC sellers recommend but TPS fits new OEM friction rings and bolt and increase the tightening TQ (by increasing the final angle added by 90 degrees) and add Loctite!

2 of those 3 things are proven fixes for bolts that "vibrate" loose

Also here is a pic of a failed CBC. As you can see the CBC bolts have been sheared off in the hub. That can only occur if the CBC spins with respect to the hub...

In that youtube vid another user complains of the same issue and another of SCH symptoms after installing the CBC.

"Enrico Rieck 1 month ago
Ich habe eine kurbelwellenverstärkung einbauen lassen bei einer werkstatt plus leistungssteigerung auf 560 PS und nach einem dreiviertel Jahr ca habe ich jetz den mist!! Versicherung zahlt nicht und ich bleib auf den Schaden sitzen!! Ich habe die kurbelwellenverstärkung selbst gekauft und der Werkstatt zum einbauen dazu gelegt.
Bei mir waren aber kurze alu schrauben dabei die sich jetzt durch das Material gedrückt haben und Drehmoment mit dem die befestigt wurden weiß ich nicht!! Meine Frage sollte die Werkstatt wissen das man solche Schrauben nicht benutzt??"

As to my test the point is to measure which one is harder to back out bolt or CBC + bolt. If it is harder to back out with CBC then it means its doing something for vibration/losening. If its about the same then the CBC is not doing anything for vibration/losening.

Anyways reading the youtube comments to that TPS vid brings out another potential problem of the CBC that I had not thought about. When the crank spins up it also spins up the bolt.

Now normally a bolt weighs too little for its moment of inertia to play a roll in the bolt backing out.

But with the CBC you attach the mass of the hub and pulley etc to the bolt increasing its moment of inertia. Thereby increasing the chances of the bolt backing out due to the loosening force exerted on it.

Its true that the hub is always rotationally held in place by the bolt. What changes is that the hub is now mechanically and frictionally rotationally held in place. The new mechanical connection transmitts the force directly to the threads of the bolt instead of the preload of the joint.

That can lead to a violent loosening of the crankhub, resulting in the sheared bolts of the failed CBC.

If anyting, increase the TQ on the hub bolt and fix it with loctite or something. That leaves out the inertia issue, solves a "vibration" issue, and increases the clamping force on all the components of the crank hub.

I'll take a look at the video later, but it might be hard due to the language barrier, thanks for the tip.

Loctite is the worst thing to put on the crank bolt, have fun trying to service the hub if it does spin, and have fun trying to clean the threads on the inside of the crank without getting bits of loctite into the block and oil supply. Also the TPS doesn't even offer much of a solution, the only true way to fix a spun hub is a SPLOCK or pinned hub solution, then a CBC on top if you truly believe in vibrations.


The bolts in the CBC image you posted looks to be a crappy grade of metal (it looks like the oem aluminium torx bolts used to hold on the damper from factory which alot of the cheaper CBC solutions use and include in their kits) which is why it gave way, that is why all the quality CBC solutions use grade 12.9 bolts. The other CBC's are extremely thin as well which is why you see the bolts sheer the capture, with a solid billet aluminium capture I doubt that would happen.



But yet, after you fix the vibration the only thing left is inertia, and the only way to do that is with the hub fix kits.

[Megator]

Originally Posted by F87source

I'll take a look at the video later, but it might be hard due to the language barrier, thanks for the tip.

Loctite is the worst thing to put on the crank bolt, have fun trying to service the hub if it does spin, and have fun trying to clean the threads on the inside of the crank without getting bits of loctite into the block and oil supply. Also the TPS doesn't even offer much of a solution, the only true way to fix a spun hub is a SPLOCK or pinned hub solution, then a CBC on top if you truly believe in vibrations.


The bolts in the CBC image you posted looks to be a crappy grade of metal (it looks like the oem aluminium torx bolts used to hold on the damper from factory which alot of the cheaper CBC solutions use and include in their kits) which is why it gave way, that is why all the quality CBC solutions use grade 12.9 bolts. The other CBC's are extremely thin as well which is why you see the bolts sheer the capture, with a solid billet aluminium capture I doubt that would happen.



But yet, after you fix the vibration the only thing left is inertia, and the only way to do that is with the hub fix kits.

I thought CBC meant all your SCH worries went away, no need to ever clean the threads again right

They use Loctite blue which I always thought was meant for joints that need to be undoable. I also thought you could just slather more on and just bolt it back in again (this is what I always do) but im not so clued up on Loctite.

The point of the pic is that the CBC did not stop SCH from hapening. The bolt grade is largely irrelevant (so long as the preload is the same), it spins first and then the bolts are sheared off. A greater grade bolt might survive or not, at that point its spun though.

It is true that higher quality parts will let you increase the preload though. This however depends on how you tighten the bolts (TQ/angle/friction of the bolt going in, etc). I have not checked the torque recepies for each hub (or if they even give one).

BTW the spline lock is proven BS. Never in a hundred years will you get some shitty splines to cut into the hardened metal of the crank unless its attached to a highspeed rotating tool which is removing 1/10-1/100 of a mm at a time. Whatever interface is created will provide a minimal amount of hold. They could easily prove it works be showing the TQ needed to spin a stock hub and a SPLOCK hub (or even that their splines scored a crank) yet you see no proof of this anywhere...

The pinned hubs have the potential to crack the crank by weakening the material at the interface, kinda like the 1st solution on the market to woodruf key the gears to the hub resulted in split timing gears.

EDIT:

BTW VTT changed thier SPLOCK hub design from a twisting spline to a straight spline. This makes perfect sense as, if the spline does indeed work, the twisted spline will rotate the hub on the crank as you tighten it (like cutting threads with a tap) but that also throws off the timing/gives you less control on the hub position. By making the splines straight one can tighten it "straight" in, in the right rotational position.

https://www.***********.com/showthre...ilable!-SPLOCK
https://vargasturbo.com/product/vtt-...khub-solution/

This is not an admission that SPLOCK works as the twisiting forces do not need to be very great to get the hub to rotate b4 it is clamped down. BTW if SPLOCK did work and you tightend it in the wrong rotational position you would be Fed and need to replace the crank.

[F87source]

Originally Posted by Megator

I thought CBC meant all your SCH worries went away, no need to ever clean the threads again right

They use Loctite blue which I always thought was meant for joints that need to be undoable. I also thought you could just slather more on and just bolt it back in again (this is what I always do) but im not so clued up on Loctite.

The point of the pic is that the CBC did not stop SCH from hapening. The bolt grade is largely irrelevant (so long as the preload is the same), it spins first and then the bolts are sheared off. A greater grade bolt might survive or not, at that point its spun though.

It is true that higher quality parts will let you increase the preload though. This however depends on how you tighten the bolts (TQ/angle/friction of the bolt going in, etc). I have not checked the torque recepies for each hub (or if they even give one).

BTW the spline lock is proven BS. Never in a hundred years will you get some shitty splines to cut into the hardened metal of the crank unless its attached to a highspeed rotating tool which is removing 1/10-1/100 of a mm at a time. Whatever interface is created will provide a minimal amount of hold. They could easily prove it works be showing the TQ needed to spin a stock hub and a SPLOCK hub (or even that their splines scored a crank) yet you see no proof of this anywhere...

The pinned hubs have the potential to crack the crank by weakening the material at the interface, kinda like the 1st solution on the market to woodruf key the gears to the hub resulted in split timing gears.

EDIT:

BTW VTT changed thier SPLOCK hub design from a twisting spline to a straight spline. This makes perfect sense as, if the spline does indeed work, the twisted spline will rotate the hub on the crank as you tighten it (like cutting threads with a tap) but that also throws off the timing/gives you less control on the hub position. By making the splines straight one can tighten it "straight" in, in the right rotational position.

https://www.***********.com/showthre...ilable!-SPLOCK
https://vargasturbo.com/product/vtt-...khub-solution/

This is not an admission that SPLOCK works as the twisiting forces do not need to be very great to get the hub to rotate b4 it is clamped down. BTW if SPLOCK did work and you tightend it in the wrong rotational position you would be Fed and need to replace the crank.

Clearly a CBC is not the full solution to the spun hub issue and I never once stated it was. So your picture just showed the hub spinning and the bolts sheared and the CBC also breaking because the materials were imo sub par. You can also see the stock aluminium bolts being reused again a bad design. A better grade bolt would not have stopped the spin because the CBC does not stop spun crank hubs fully as been stated before. What the better grade bolts would do is stop it from rotating any further not that it would matter at that point, but atleast you do not have the crank bolt be loosen any further than would be allowed by the groove in the CBC.

25 foot pounds is the torque specs.

Blue loctite is removable but still at a significant torque, you also leave a bunch of residue inside of the threads which need to be cleaned out for new loctite to react with the metal in an anaerobic fashion. This could cause small bits of loctite to fall inside of the block.


How do you know the splock is proven BS? Is it more speculation like the unbalanced crank guess? Because V1 SPLOCK splines did fail, V2 straight cut splines are press fit into the crank and they do cut into it, there are images if you searched instead of guessed that it didn't cut into the crank.

Images were posted by VTT on another forum.

View post on imgur.com

View post on imgur.com

Looks like they cut in pretty well to me.


They managed to break a stock crank with this amount of interface without slipping, so seems pretty good since the torque needed to spin this exceeded what could be handled by the crank shaft. Even if they knew what torque a stock crank hub would spin at they wouldn't publish it because that is R&D data and that costs money to obtain and why would they give that to the competition for free? All the data a customer needs to know is that this can hold enough torque that a crank will break first, they posted their testing apparatus online too. I don't know what more you could expect.


Where is your proof that the pinned hubs weakend the crank? So far all of the crank shafts that have been done are fine, the crank is hard enough and durable enough that is doesn't crack or fail due to the pin holes. As you can see on the abundance of cars that have the max psi solution, and max psi's 1000whp+ shop car, Carbahm motorsports (steve dinan's shop) is using a pinned hub too and they warranty their engines showing how their team of engineers can stand behind the design to back it with their own dollar.


The woodruf solution was faulty that is why the designs have changed, the final solution is durable and has now been proven. There were many attempts to perfect this design and many failed along the way (TPG was the worst imo).


Yes I know VTT has a rev 2 out because the Rev 1 failed.

I believe what they did to prevent timing jumps was cut the threads from the beggining so it doesn't shift. Any minor shift would be so small it wouldn't even matter as the spacing on the timing chain would be larger that that shift so there would be no way it could jump teeth on the chain, and it would likely just add a minuscule mount of tension to the timing chain and that would be it.


You don't need to worry about tightening the crank wrong if you used the proper torquing bar (shown in the video by abr) and let it rest on the ground or on a solid object while torquing the crank bolt.


Overall I am pretty tired of replying to this thread since these issues do not pertain to the n55 unless you money shift, if you want to know more about the VTT solution you should contact them or read all their threads since all the info is posted there.

[Megator]

Originally Posted by F87source

Clearly a CBC is not the full solution to the spun hub issue and I never once stated it was. So your picture just showed the hub spinning and the bolts sheared and the CBC also breaking because the materials were imo sub par. You can also see the stock aluminium bolts being reused again a bad design. A better grade bolt would not have stopped the spin because the CBC does not stop spun crank hubs fully as been stated before. What the better grade bolts would do is stop it from rotating any further not that it would matter at that point, but atleast you do not have the crank bolt be loosen any further than would be allowed by the groove in the CBC.

25 foot pounds is the torque specs.

Blue loctite is removable but still at a significant torque, you also leave a bunch of residue inside of the threads which need to be cleaned out for new loctite to react with the metal in an anaerobic fashion. This could cause small bits of loctite to fall inside of the block.


How do you know the splock is proven BS? Is it more speculation like the unbalanced crank guess? Because V1 SPLOCK splines did fail, V2 straight cut splines are press fit into the crank and they do cut into it, there are images if you searched instead of guessed that it didn't cut into the crank.

Images were posted by VTT on another forum.

View post on imgur.com

View post on imgur.com

Looks like they cut in pretty well to me.


They managed to break a stock crank with this amount of interface without slipping, so seems pretty good since the torque needed to spin this exceeded what could be handled by the crank shaft. Even if they knew what torque a stock crank hub would spin at they wouldn't publish it because that is R&D data and that costs money to obtain and why would they give that to the competition for free? All the data a customer needs to know is that this can hold enough torque that a crank will break first, they posted their testing apparatus online too. I don't know what more you could expect.


Where is your proof that the pinned hubs weakend the crank? So far all of the crank shafts that have been done are fine, the crank is hard enough and durable enough that is doesn't crack or fail due to the pin holes. As you can see on the abundance of cars that have the max psi solution, and max psi's 1000whp+ shop car, Carbahm motorsports (steve dinan's shop) is using a pinned hub too and they warranty their engines showing how their team of engineers can stand behind the design to back it with their own dollar.


The woodruf solution was faulty that is why the designs have changed, the final solution is durable and has now been proven. There were many attempts to perfect this design and many failed along the way (TPG was the worst imo).


Yes I know VTT has a rev 2 out because the Rev 1 failed.

I believe what they did to prevent timing jumps was cut the threads from the beggining so it doesn't shift. Any minor shift would be so small it wouldn't even matter as the spacing on the timing chain would be larger that that shift so there would be no way it could jump teeth on the chain, and it would likely just add a minuscule mount of tension to the timing chain and that would be it.


You don't need to worry about tightening the crank wrong if you used the proper torquing bar (shown in the video by abr) and let it rest on the ground or on a solid object while torquing the crank bolt.


Overall I am pretty tired of replying to this thread since these issues do not pertain to the n55 unless you money shift, if you want to know more about the VTT solution you should contact them or read all their threads since all the info is posted there.

I had not seen thoose pics, and didnt find anything when I searched. Thoose pics bring another issue to light and that is the material bunched up at the end of the root of the spline. They could prevent the hub from being compressed as much as it should. This can be designed for by making the hub a little shorter though.

The anerobic conditions exist whether hardened loctite is left behind or not.

I read in some thread that the SPLOCK was BS from someone that installed it.

Everything is theoretical as I dont have access to test rigs. Removing material weakens things, that is a fact. The question is whether the removal of material weakens things too much to the point where they break (like the TPG solution).

The same occurs with the SPLOCK, the pressure the SPLOCK exerts on the hub of the crank by expanding it out could cause failure. This is known as hoop stress.

Just like I speculate with education as backing, tuners do not do the testing an OEM does and that covers the wide spectrum of tolerances present (geometric, thermal, loads, material, etc).

They also dont test their solutions over 10,20,30-100k km/miles of engine running where FATIGUE failures will show.

BTW absence of failures does not necessarilly mean a solution worked.

Info and tests can be faked and can be carried out wrong. One should take marketing hype with a large pinch of salt.

Your whole bit about the chain and tightening makes no sense. The pitch of the chain is not the issue and it will have been selected with the gears in mind. The issue is that each timing gear needs to be in a particular position with respect to each other and the camshats/crank. A twisted spline makes getting this all lined up more difficult.

BTW you are in the S55 section...and no one is asking you to reply.

Final argument from me. Tuners are not OEMs, they do not have the engineering capabilities and do the validation testing that an OEM does.

Their solutions for this complex and expensive issue will be bandaids addressing the symptoms and not necessarily the root cause. Their solutions might also overlook subtle issues that apear much later than they care to test their solutions for.

When you modify your vehicle, without fully knowning what you are doing, you might cause more harm than good. Think twice about any modification and what knock on effects it might have.

[F87source]

Originally Posted by Megator

I had not seen thoose pics, and didnt find anything when I searched. Thoose pics bring another issue to light and that is the material bunched up at the end of the root of the spline. They could prevent the hub from being compressed as much as it should. This can be designed for by making the hub a little shorter though.

The anerobic conditions exist whether hardened loctite is left behind or not.

I read in some thread that the SPLOCK was BS from someone that installed it.

Everything is theoretical as I dont have access to test rigs. Removing material weakens things, that is a fact. The question is whether the removal of material weakens things too much to the point where they break (like the TPG solution).

The same occurs with the SPLOCK, the pressure the SPLOCK exerts on the hub of the crank by expanding it out could cause failure. This is known as hoop stress.

Just like I speculate with education as backing, tuners do not do the testing an OEM does and that covers the wide spectrum of tolerances present (geometric, thermal, loads, material, etc).

They also dont test their solutions over 10,20,30-100k km/miles of engine running where FATIGUE failures will show.

BTW absence of failures does not necessarilly mean a solution worked.

Info and tests can be faked and can be carried out wrong. One should take marketing hype with a large pinch of salt.

Your whole bit about the chain and tightening makes no sense. The pitch of the chain is not the issue and it will have been selected with the gears in mind. The issue is that each timing gear needs to be in a particular position with respect to each other and the camshats/crank. A twisted spline makes getting this all lined up more difficult.

BTW you are in the S55 section...and no one is asking you to reply.

Final argument from me. Tuners are not OEMs, they do not have the engineering capabilities and do the validation testing that an OEM does.

Their solutions for this complex and expensive issue will be bandaids addressing the symptoms and not necessarily the root cause. Their solutions might also overlook subtle issues that apear much later than they care to test their solutions for.

When you modify your vehicle, without fully knowning what you are doing, you might cause more harm than good. Think twice about any modification and what knock on effects it might have.

I just wanted to apologize because I re-read my last statement and I sounded like an A-hole with how I ended it. I typed it quite quick on my phone and it sounded better in my head than I thought it would come out.

What I meant to say was that we were repeating the same talking points over and over with not too much data to prove if the CBC worked or if the current hub solutions were safe long term except speculations from testing from users, that I really had not much left to say (since I have an n55 so these issues aren't relevant to me and I just wanted to initially bring up some potential solutions and info I had learned to help the S55 guys) so I was going to end my participation as the issues boiled down to the same issues and since you had interesting topics you brought up as you are an engineer and see things differently than me it would be best if you talked to the engineers that made this directly.

Also one quick point if you are going to use loctite, it requires anaerobic conditions and the presence of active metals. So if you do not clean out old residue it will form a gunky layer that will not let the metal ions react with the new loctite and it will not react and work.

Also you are correct, these solutions are a band aid at best, but imo better a band aid than nothing else especially for people pushing the envelope in racing situations where they cannot afford to have the car fail.

So sorry if I sounded/came across like a jerk, it was not my intention.