N54 crank hub issue - power level?

[kayzrx82]

so what are people's thoughts on the vtt option vs the maximum psi option, despite it being cheaper?

https://bmw.spoolstreet.com/threads/maximum-psi-keyed-crank-hub.3145/

Ive installed a couple of the maximum psi hubs . They work well but require drilling the crank. I'm currently building a motor for myself and was waiting on the vtt solution to weigh my options on this next build. It seems like an elegant solution and I like how it doesn't require drilling the crank and can be installed without dropping the pan. I would just like some numbers on the torque they were seeing the stock hub slip at vs the torque the spline lock hub broke the rig at. I would also like to see what the splines are doing to the snout of the crank once it is installed and removed.

 

[fmorelli]

I would just like some numbers on the torque they were seeing the stock hub slip at vs the torque the spline lock hub broke the rig at.

May I offer a different perspective? From some of the comments I've heard, it seems that "breakaway torque" is more the issue. Conceptually somewhat like velocity vs acceleration. Change in force, and at what torque level, may be the issue at hand?

IMHO this kind of splined design will only see a metal fatigue failure - of the spline hub or of the crank where the splines make contact. ME's and material guys feel free to speak up, but I suspect the spline geometry and differences in the metallurgy of the two parts are the driving factors.

What I understand from Chris' shorthand on the splines driving deeper - once in there they actually don't really go anywhere - the point is that the force drives the hub in the direction of clamping force, not away. I thought that pretty obvious but given Rob's question, thought I'd say it differently here if others might have misunderstood the point.

I like the solution. I have to decide whether I should include it in my winter updates.

Filippo

 

[Rob@RBTurbo]

It is pretty clear one solution is actually a true, positive lock, setup. Once done, it is done forever, it will never steer you astray, and is clearly serviceable whenever/wherever needed. The other is a solution that is more so a "vice grip" sort of concept and appears to be a bit gimmicky.

The new splined solution although elegantly thought out and a nice overall part, has been marketed to "just dig deeper" if a spin event where to ever happen. This just is not true, obviously, as our fairly constructive post was moved to the octagon and we were banned from posting in the thread for making these comments... par for the course when there is no real rebuttal.

The meat and potatoes of this comes down to really one thing- how much are the splines digging into to the crank and thus what kind of trace mark are they leaving and is it really enough to be considered a positive lock under all scenarios. One must consider to install the splined hub they are literally pressing it on via threading in the hub bolt, if a dedicated install tool is not eventually provided (ie. using a separate long stud, and a thread on nut/washer); which will limit you on the pressing force that even can be achieved in the first place. The question then lies of what kind of negative clearance is utilized using such a process? This is important as this negative clearance is what actually will allow some groove etching to take place, and is likely sub .003" as it would take a LOT of pressing force to etch these parts as the clearance lessens. Too much pressing force, especially without a pressing tool, the inner crank threads could even be at stake. One must also consider that there will likely be some deviation to the timing relationship as the hub is pressed into position due to the non-straight cut splines, and also consider that the groove may not leave a perfect line for future servicing if needed. Honestly I'd suspect straight cut splines would've been just as effective, hold better position for timing relationships during install, provide a more usable path trace for future servicing, and allow just as much groove etching to attempt to hold the components as one.

Ultimately things like this take many samples, many variables, and much time to see how they are going to pan out. A single vendor using the splined solution successfully for 8+ months could be just as good as another vendor using the OEM setup successfully for 8+ months; or in other words be worth no more than the paper the idea is printed on. As always items like this are best tossed out to a group of guys who truly are pushing the envelope, immediately, and all of the time. Give this group of guys a year+ with it, and if they all have positive feedback along with extreme performance results to back it then that would be some compelling evidence. Until then if you want something that is truly a positive lock and a no-nonsense anti-slip sort of product; the Maximum PSI is going to be the way to go. Sometimes you get what you pay for (whether time or money or both) out there, other times you are simply beta testing.

Rob

 

[MoreBoost]

I don't understand why the sprocket can't just slip on the vtt one? It's still using just a washer to rotate with the crank?
This is why I prefer other options, even if it does mean more overhead costs to install.

The maximum psi one looks guaranteed to never fail. From what I've read they managed to break a gintani solid piece hub fix.

http://gintani.com/product/gintani-f8x-m3-m4-one-piece-crank-hub-solution/

 

[kayzrx82]

May I offer a different perspective? From some of the comments I've heard, it seems that "breakaway torque" is more the issue. Conceptually somewhat like velocity vs acceleration. Change in force, and at what torque level, may be the issue at hand?

IMHO this kind of splined design will only see a metal fatigue failure - of the spline hub or of the crank where the splines make contact. ME's and material guys feel free to speak up, but I suspect the spline geometry and differences in the metallurgy of the two parts are the driving factors.

What I understand from Chris' shorthand on the splines driving deeper - once in there they actually don't really go anywhere - the point is that the force drives the hub in the direction of clamping force, not away. I thought that pretty obvious but given Rob's question, thought I'd say it differently here if others might have misunderstood the point.

I like the solution. I have to decide whether I should include it in my winter updates.

Filippo

I understand the concept behind the spline lock and I think it is an effective lock to the crank given the bolt does not stretch and the teeth are defroming or cutting a spline into the snout of the crank. My concern is the repeatabilty of the lock, how it works after it has been removed for servicing, and how effective it is of the bolt we're to strecth since it is using the stock bolt which has been know to stretch ad certain power levels. The break away torque from resting means very little to what's happening in a running crank at high rpm and power level at that point of the crank. Harmonics, and changes in velocity of the crank can impact forces well beyond the breakaway torque. Think of how an impact wrench works. If we can get a number as to what break away torque caused the crank to slip or break their rig you can at least have a safety factor to base what it will break at. Harmonics can impart 3 to 6x the forces on the crank at the cranks harmonic frequency. When I was in undergrad we did analysis of harmic forces on parts. The forces, given the right frequency can cause immense damage. Even though Inline 6 engines are balanced first and second order, the crank has to deal with a ton of harmonic forces that the dampener has to dissipate as heat. I personally would just like to see more data.

 

[kayzrx82]

I don't understand why the sprocket can't just slip on the vtt one? It's still using just a washer to rotate with the crank?
This is why I prefer other options, even if it does mean more overhead costs to install.

The maximum psi one looks guaranteed to never fail. From what I've read they managed to break a gintani solid piece hub fix.

http://gintani.com/product/gintani-f8x-m3-m4-one-piece-crank-hub-solution/

The washer part is the oil pump, vac pump, and hpfp drive gear .The hub has a machined on gear that runs the cams. That part is what gets splined into the crank .

 

[kayzrx82]

It is pretty clear one solution is actually a true, positive lock, setup. Once done, it is done forever, it will never steer you astray, and is clearly serviceable whenever/wherever needed. The other is a solution that is more so a "vice grip" sort of concept and appears to be a bit gimmicky.

The new splined solution although elegantly thought out and a nice overall part, has been marketed to "just dig deeper" if a spin event where to ever happen. This just is not true, obviously, as our fairly constructive post was moved to the octagon and we were banned from posting in the thread for making these comments... par for the course when there is no real rebuttal.

The meat and potatoes of this comes down to really one thing- how much are the splines digging into to the crank and thus what kind of trace mark are they leaving and is it really enough to be considered a positive lock under all scenarios. One must consider to install the splined hub they are literally pressing it on via threading in the hub bolt, if a dedicated install tool is not eventually provided (ie. using a separate long stud, and a thread on nut/washer); which will limit you on the pressing force that even can be achieved in the first place. The question then lies of what kind of negative clearance is utilized using such a process? This is important as this negative clearance is what actually will allow some groove etching to take place, and is likely sub .003" as it would take a LOT of pressing force to etch these parts as the clearance lessens. Too much pressing force, especially without a pressing tool, the inner crank threads could even be at stake. One must also consider that there will likely be some deviation to the timing relationship as the hub is pressed into position due to the non-straight cut splines, and also consider that the groove may not leave a perfect line for future servicing if needed. Honestly I'd suspect straight cut splines would've been just as effective, hold better position for timing relationships during install, provide a more usable path trace for future servicing, and allow just as much groove etching to attempt to hold the components as one.

Ultimately things like this take many samples, many variables, and much time to see how they are going to pan out. A single vendor using the splined solution successfully for 8+ months could be just as good as another vendor using the OEM setup successfully for 8+ months; or in other words be worth no more than the paper the idea is printed on. As always items like this are best tossed out to a group of guys who truly are pushing the envelope, immediately, and all of the time. Give this group of guys a year+ with it, and if they all have positive feedback along with extreme performance results to back it then that would be some compelling evidence. Until then if you want something that is truly a positive lock and a no-nonsense anti-slip sort of product; the Maximum PSI is going to be the way to go. Sometimes you get what you pay for (whether time or money or both) out there, other times you are simply beta testing.

Rob

Good points. That's one of the reasons I had asked to see a picture of what the splines were doing to the snout of the crank once installed and removed. If it is indeed keying splines onto the snout then yes I think this solution will work given the bolt does not back out hence why they tell you to run the bolt lock with it . Only time will tell how harmonics come into play with this. I'm concerned with the bolt stretching. I think most of these hubs slip due to stretching of the bolt and not so much the bolt backing out. If the splines rely on the clamping force of the bolt to keep it locked there may be an issue. The M psi hub doesn't need the clamping force of the bolt to keep the gear locked in place, just to hold the hub in position. I like the vtt spline lock solution as you don't have to drop the pan to install it and you don't have to drill the crank. My main concerns is if the spline fail ,ex. stretching of the bolt, harmonic forces, what happens to the snout of the crank? Is it reusable? Will another spline hub be able to still have enough engagement to be effective? If it fails am I going to be sourcing a new crank ? The mPSI is no doubt proven but the vtt one I believe can be a much better lock given the bolt doesn't stretch. I'm going to give it a try on the next build.

 

[The Convert]

Personally, I like that Chris and Tony are putting in work to get more products out there for us, but I don’t think this one meets the mark for me. The maximum psi solution is superior based on the data I’ve seen.

I asked in the other thread what the combined cross-sectional area of the spline faces was because that will tell you how much area is taking the load the splines will see. Then compare that and the material properties of the two hub options and it should be pretty easy to determine which option is better.

If I had to choose, I’d go max psi and add a VTT bolt capture.

 

[Chris@VargasTurboTech]

It's a flawed analysis to compare area of a key to area of splines that drive the force in the direction of clamping. You'd want to consider all aspects of the design, and what the role of the key vs. splines is, not just pick something simple like area and run with a direct comparison. They are two different methods of the system achieving the same goal, but they do not serve the same function.

 

[Rob09msport]

Two things one is if the splines were the only thing preventing a slip I could see the concern but you have to take in consideration that they are in addition to the standard install and grip disc. Also as far as the bolt stretching this is when the statement about pulling in tighter applies. The forces from the hub trying to slip will be holding things together not pulling apart. As long as a new bolt is used with a capture it should be pretty reliable. Main point is this doesnt change the method of securing the hub but only adds to it.

 

[MoreBoost]

The washer part is the oil pump, vac pump, and hpfp drive gear .The hub has a machined on gear that runs the cams. That part is what gets splined into the crank .

Ah I see. Makes sense. Thanks

Good points. That's one of the reasons I had asked to see a picture of what the splines were doing to the snout of the crank once installed and removed. If it is indeed keying splines onto the snout then yes I think this solution will work given the bolt does not back out hence why they tell you to run the bolt lock with it . Only time will tell how harmonics come into play with this. I'm concerned with the bolt stretching. I think most of these hubs slip due to stretching of the bolt and not so much the bolt backing out. If the splines rely on the clamping force of the bolt to keep it locked there may be an issue. The M psi hub doesn't need the clamping force of the bolt to keep the gear locked in place, just to hold the hub in position. I like the vtt spline lock solution as you don't have to drop the pan to install it and you don't have to drill the crank. My main concerns is if the spline fail ,ex. stretching of the bolt, harmonic forces, what happens to the snout of the crank? Is it reusable? Will another spline hub be able to still have enough engagement to be effective? If it fails am I going to be sourcing a new crank ? The mPSI is no doubt proven but the vtt one I believe can be a much better lock given the bolt doesn't stretch. I'm going to give it a try on the next build.

I think you could be right. Probably a series of these events over time weaken, back out or stretch the bolt securing the whole system. I think for now I will secure that bolt to the hub. Going for a full keyed hub replacement is probably getting towards the cost of a replacement engine these days once hardware and install costs are factored in.

 

[kayzrx82]

Two things one is if the splines were the only thing preventing a slip I could see the concern but you have to take in consideration that they are in addition to the standard install and grip disc. Also as far as the bolt stretching this is when the statement about pulling in tighter applies. The forces from the hub trying to slip will be holding things together not pulling apart. As long as a new bolt is used with a capture it should be pretty reliable. Main point is this doesnt change the method of securing the hub but only adds to it.

Pulling in tighter would make things worse if the bolt we're stretched. I dont think there is any physical moving of the hub to the spline after it is installed . The hub would have to compress the gear or washer to do so . In the event the bolt were to strech the splines are the only thing holding the hub in time with the crank . I'm not saying this won't work, I think the splines is a great idea and will hold given clamping force is held on the hub. I'm just concerned with the factory bolt which has been known to stretch. It is designed to stretch when installing to hold the clamping load on the hub. My thoughts are the bolt stretches further after a while causing it to loose it's clamping force on the hub. Whether this strecthing is due to harmonic forces on the crank, or just an out of spec fastener is what is unknown. I think this solutions with a higher rated fastener would get rid of the possibility of the bolt stretching and make this a bullet proof hold. Harmonics can put forces in excess of what is being generated by the motor. The crank turns into a tuning fork vibrating at it's renonate frequency. The dampener turns those vibrations into heat, but it has to pass through the snout and hub to get to the dampener. Inline 6 cranks are prone to harmonic stresses due to the length of the crank.

 

[Hydra Performance]

The torsional oscillations @ the damper are only on the order of a few degrees, call it <20deg even in a resonance mode with a safety factor built in. I doubt the bolt is stretched that close to its elastic limit, so I very much doubt that the bolt really stretches any in actual operation, especially if a bolt capture kit is installed which prevents harmonics from ever backing out the bolt (which would reduce tension and promote hub slippage)

 

[Rob09msport]

Pulling in tighter would make things worse if the bolt we're stretched. IIdont think there is any physical moving of the hi due to the spline after it is installed . The hub would have to compress the gear or washer to do so . In the event the bolt were to strech the splines are the only thing holding the hub in time with the crank . I'm not saying this won't work, I think the splines is a great idea and will hold given clamping force is held on the hub. I'm just concerned with the factory bolt which has been known to stretch. It is designed to stretch when installing to hold the clamping load on the hub. My thoughts are the bolt stretches further after a while causing it to loose it's clamping force on the hub. Whether this strecthing is due to harmonic forces on the crank, or just an out of spec fastener is what is unknown. I think this solutions with a higher rated fastener would get rid of the possibility of the bolt stretching and make this a bullet proof hold. Harmonics can put forces in excess of what is being generated by the motor. The crank turns into a tuning fork vibrating at it's renonate frequency. The dampener turns those vibrations into heat, but it has to pass through the snout and hub to get to the dampener. Inline 6 cranks are prone to harmonic stresses due to the length of the crank.

I def agree that I don't think anything moves it just is hard to put into words sometimes. I was trying to say that the excessive force that the hub exerts on the splines when it would have slipped are pulling in but that should only take place if it is an event where it would have slipped to begin with. This I am not sure of though as I don't know the ratio of how the forces distribute.

 

[Terry@BMS]

I don't understand why the sprocket can't just slip on the vtt one? It's still using just a washer to rotate with the crank?
This is why I prefer other options, even if it does mean more overhead costs to install.

The maximum psi one looks guaranteed to never fail. From what I've read they managed to break a gintani solid piece hub fix.

http://gintani.com/product/gintani-f8x-m3-m4-one-piece-crank-hub-solution/

Nothing is every guaranteed never to fail. I've seen machined hubs crack in half before, wood ruff keys sheered, etc. You're dealing with a lot of force there and anything non-symmetrical that does not spread that load across the entire crank snub is going to be suspect. That said I don't know what the best solution is but obviously have the VTT solution on our VTT built motor. Since N54s do not have a reputation for spinning the hubs, like say the S55 motor does, hopefully it never lets me down.

 

[Rob@RBTurbo]

Nothing is every guaranteed never to fail. I've seen machined hubs crack in half before, wood ruff keys sheered, etc. You're dealing with a lot of force there and anything non-symmetrical that does not spread that load across the entire crank snub is going to be suspect. That said I don't know what the best solution is but obviously have the VTT solution on our VTT built motor. Since N54s do not have a reputation for spinning the hubs, like say the S55 motor does, hopefully it never lets me down.

Good point on the S55 vs. N54 crank hub issues. It'll be interesting to see how the spline setup works out across platforms- especially those that are more prone to the issues to begin with such as with some S55's.

As for the N54 crank hub issues it seems that some have claimed to have tremendous issues with it, although as you state it seems to not have a reputation for it. Have you ever spun an N54 crank hub yourself or seen it happen up close and personal? Everything we hear about on the N54 engine failure front is simply popped pistons it seems.

 

[kayzrx82]

Good point on the S55 vs. N54 crank hub issues. It'll be interesting to see how the spline setup works out across platforms- especially those that are more prone to the issues to begin with such as with some S55's.

As for the N54 crank hub issues it seems that some have claimed to have tremendous issues with it, although as you state it seems to not have a reputation for it. Have you ever spun an N54 crank hub yourself or seen it happen up close and personal? Everything we hear about on the N54 engine failure front is simply popped pistons it seems.

I personally have had one spin on me. N54 six speed. Happend on a shift from first to second. Bent the exhaust valves and a few of the intake valves. snapped the timming chain as well. I've also installed 2 of the mPSI hubs for a couple people in Orlando that spun the hubs on their n54 motors. One was an auto. The other due to a money shift. The whole idea of relying on a bolt and friction to keep the hub in time instead of a key was a dumb idea from BMW .

 

[Rob09msport]

I personally have had one spin on me. N54 six speed. Happend on a shift from first to second. Bent the exhaust valves and a few of the intake valves. snapped the timming chain as well. I've also installed 2 of the mPSI hubs for a couple people in Orlando that spun the hubs on their n54 motors. One was an auto. The other due to a money shift. The whole idea of relying on a bolt and friction to keep the hub in time instead of a key was a dumb idea from BMW .

Honestly I look at it like we are lucky that BMW made it so easy to attain power levels that we have issues like this. For their intended application the n54 is pretty solid, just so happens their are a few things that werent over engineered to the same level. This is why I think if we made it this far way we have a little extra holding power should be plenty , for the n54 at least.

 

[kayzrx82]

Honestly I look at it like we are lucky that BMW made it so easy to attain power levels that we have issues like this. For their intended application the n54 is pretty solid, just so happens their are a few things that werent over engineered to the same level. This is why I think if we made it this far way we have a little extra holding power should be plenty , for the n54 at least.

I agree. The n54 is a solid motor. It's just the hub is like the Achilles heel of these things motor wise, not looking at the support
hardware ( injectors, hpfp, etc.)
I've worked on various motors from jaguar, Mercedes, Ford's, Chevys etc. They usually key the hub or timing gear, have it machined onto the crank, gear driven, or bolted in a way that more then one fastener holds the gear that times the motor. BMW went to the friction style hub for several reasons. By having the hub separate from the crank they can have a one peice timing chain cover that is part of the block. This speeds assembly cuts cost on the block and is one less leak point and sealing surface to deal with. Also allows for a modular approach thoughout the engines they produce. It allows for easier manufacturing by speeding up assemble and automation is easier. It cost less and is faster to produce the crank without having to cut keys, grooves or machine the timing gear into it. Overall it's a great design for cost savings and automating the assembly process. I just think they could have done it differently taking into account that an interference motor doesn't do well loosing time. The one that slipped on me was stock. That's why I think the friction disk work fine as long as clamping force is maintained. But somehow over time it looses that force. I think it's from stretching. Some say it's from the bolt backing out. Could be the friction disk compressing over time. Who knows.

 

[Rob@RBTurbo]

I have seen one (local friend) that had the hub bolt back out, which of course made the hub slip. But he'd just had it in for servicing a few miles prior for the front seal replacement (after a belt shredding) and we suspected that even though the hub bolt doesn't need tampered with that somehow it was anyway. Or could've been a freak coincidence and from a money shift or something, as it was a Manual car. Could've even had something to do with the belt shred itself, possibly, as ripping that belt into the crank pulley could certainly cause some strains as seen by the crank pulley that could affect the hub bolt. Either way freak ordeal that could've been avoided by a keyed hub, but certainly wasn't power related as this car probably was making about 350whp at best (100% stock with pump gas tune only).

With the spline lock it seems that it is going to only aid, rather than "lock", by providing more of a internal vice grip like lock on the crank inner hub. Vice grips definitely help as we all know, but we also know they can slip with relative ease too. It is a tool most of us know better than try to utilize unless in some sort of jam, as they can mar up surfaces in a jiffy (even if they don't give). And while it certainly seems it would help I just can't fathom it being the end all be all like some of the other positive keyed offerings, and as it is still highly reliant on the crank bolt staying positioned the crank bolt capture would be something to never pass on either. If I were to install one I'd definitely be wanting to not use the bolt to press it into place but rather some sort of simple hub install tool... primarily to keep the new hub bolt torque to yield as spot on as possible prior to installing the crank bolt capture. Still am curious to see the trace path that are etched by the splines into the crank ID as well, post up if anyone has seen such a picture.

It is safe to say at this point that everyone agrees that a key of sorts would be the best for the most positive locked solution here. Additionally these keyed offerings are being pushed to severe levels on much more prone platforms, whichever stands the strongest for the longest would be ideal- can't help but feel that is the Maximum PSI unit so far. Plus these guys are die hard drag racing lunatics that push things harder than anyone, literally, anyone. I spoke to them before they even bought that M3, they bought it for one reason and that was to push it to hell and back starting day 1 (he wanted a turbo upgrade before they even had the car in hand yet, for starters). Apparently now they have been there and done that with all other ideas that ultimately gave out on them too, which led to where they are at today. But indeed, more costly and a further pain to install.

Going to be interesting to follow along and hopefully the forums are presented with the outcomes whether good or bad on them all over time.

Rob