Vargas Crank Bolt Capture Installed

[///BMW Junkie]

Originally Posted by CloudVIII

Yes just the capture in place.

How many miles now with the bolt capture?

[FSociety]

Originally Posted by ///FASTDAD

How many miles now with the bolt capture?

Last he said 15k miles so far and he's got more power than before too

[blockdoc]

Originally Posted by FSociety

Last he said 15k miles so far and he's got more power than before too

Im biased because I just sprung for the whole shebang...but if you are considering high power and are gonna do part...may as well do the whole fix.

Interesting....Autotalent called on my 2015 and found that the bushing had been fused to the hub previously and may have spun. There is no service history that mentions anything about this, but they surmised that BMW may have "fixed this" early on?

Glad I went full monty on this one...new turbos on now

[mfurse]

Is it just me or does the new S58 look like it features a crank case capture?

[The_E92_Fan]

Have ANY N54 cars with the crank bolt capture failed? Looking specifically at 335is with DCT

[tom @ eas]

Originally Posted by The_E92_Fan

Have ANY N54 cars with the crank bolt capture failed? Looking specifically at 335is with DCT

Might be best to check in in the other forums.

[The_E92_Fan]

Perhaps I could expand my target audience. Could anyone here say for certain that there have been less failures in problematic model year S55's with only the VTT capture?

[tom @ eas]

Originally Posted by The_E92_Fan

Perhaps I could expand my target audience. Could anyone here say for certain that there have been less failures in problematic model year S55's with only the VTT capture?

VTT recommends both Splinelock and CBC are installed together. You are still at risk (likely less than if no action taken at all) if only installing CBC on S55.

[The_E92_Fan]

Originally Posted by tom @ eas

VTT recommends both Splinelock and CBC are installed together. You are still at risk (likely less than no no action taken at all) if only installing CBC on S55.

I definitely understand that. Im researching failures in the N54 cars in comparison to the S55 cars, specifically the DCT. Im certain when the time comes I'll install both. After a bit more research, I've read that bolts backing out are less common on the N54 anyways because the bolts apparently have an extra 90* torquing when compared to the N55 and S55.

[espressoo]

Originally Posted by CloudVIII

Ya it seems to be working for me.

Bringing back this thread from the dead but has this held up? If so, how many miles after install so far?

[CloudVIII]

Originally Posted by espressoo

Bringing back this thread from the dead but has this held up? If so, how many miles after install so far?

Ya still going about 30k miles total on it.

[MR_X]

Originally Posted by The_E92_Fan

I definitely understand that. Im researching failures in the N54 cars in comparison to the S55 cars, specifically the DCT. Im certain when the time comes I'll install both. After a bit more research, I've read that bolts backing out are less common on the N54 anyways because the bolts apparently have an extra 90* torquing when compared to the N55 and S55.

When I was looking at this a while back, I noticed this also, but the N54 has different parts than the S55 which may explain why it may have higher torque values. N55 share the same parts as the S55 and have the same torque values. I would research the N55s. Also this design is shared on numerous other BMW engines including M5s.

I'm spit balling here but I don't think the crank hub bolt is the issue. I think the issue is the crankshaft itself. Reminds me of early 5spd NSX transmissions that had a grove machined with worn tools and were out of spec causing input or output shaft in the transmission to move too much causing it them to fail. This was on random transmissions.

[espressoo]

Glad to hear it’s held up. What HP and torque are you pushing nowadays?

[MisterF80M3]

We need a CBC only master thread.

But here is the main one. Still zero documented spun crank hub with a capture.

https://f80.bimmerpost.com/forums/sh....php?t=1597456

[Chris@VargasTurboTech]

Originally Posted by The_E92_Fan

I definitely understand that. Im researching failures in the N54 cars in comparison to the S55 cars, specifically the DCT. Im certain when the time comes I'll install both. After a bit more research, I've read that bolts backing out are less common on the N54 anyways because the bolts apparently have an extra 90* torquing when compared to the N55 and S55.

Originally Posted by MR_X

When I was looking at this a while back, I noticed this also, but the N54 has different parts than the S55 which may explain why it may have higher torque values. N55 share the same parts as the S55 and have the same torque values. I would research the N55s. Also this design is shared on numerous other BMW engines including M5s.

I'm spit balling here but I don't think the crank hub bolt is the issue. I think the issue is the crankshaft itself. Reminds me of early 5spd NSX transmissions that had a grove machined with worn tools and were out of spec causing input or output shaft in the transmission to move too much causing it them to fail. This was on random transmissions.

Yep, the whole reason we got into the crank hub business was that Tony kept spinning the shop N54 crank hub. This with both the 6MT and (later) the sequential (DCT like for spitballing purposes). It pooched us quite a few times prior to us figuring out the complete solution.

What we learned was that there are 2 major causes of slipping the hub. And yes, we've done 'em both. They both are ultimately insufficient clamping force related, but one is due to the bolt vibrating loose and losing clamping force, the second mechanism is overcoming the torque capacity (dictated by clamping force) of the assembly itself.

N54's are a little better from the factory but are still susceptible.

Chris

[MJ6]

Has anyone mathematically inclined attempted to determine exactly what the friction coefficient is for the friction disks given the clamping load provided by the crank bolt?

I'm no mechanical engineer, but I'd assume that given a known clamping force and friction coefficient, one should be able to determine the load required to overcome the torque capacity of the stock crank hub.

If clutch manufacturers are able to state clamp load forces which will hold up to xxx amount of torque/hp, it's not infeasible to say that the same couldn't be done here to determine at what power levels you become a higher risk. Without solid numbers to support it, stating that it "could happen" if you only have the crank bolt capture installed is anecdotal at best.

To be clear, there's no doubt in my mind that by splining or pinning the crank hub you provide a more permanent fix, but without definitive figures I find it difficult to justify spending an additional $3k plus over just installing a CBC. It has nothing to do with being cheap either, it's the same premise as to why you wouldn't upgrade your clutch to one rated to hold 800+ torque when you're only running at stock power levels: it's just not necessary. Until we know how much power it takes to overcome the friction washers, the answer to what level of a solution is actually needed is (to me at least) nebulous.

[MR_X]

Originally Posted by Chris@VargasTurboTech

Yep, the whole reason we got into the crank hub business was that Tony kept spinning the shop N54 crank hub. This with both the 6MT and (later) the sequential (DCT like for spitballing purposes). It pooched us quite a few times prior to us figuring out the complete solution.

What we learned was that there are 2 major causes of slipping the hub. And yes, we've done 'em both. They both are ultimately insufficient clamping force related, but one is due to the bolt vibrating loose and losing clamping force, the second mechanism is overcoming the torque capacity (dictated by clamping force) of the assembly itself.

N54's are a little better from the factory but are still susceptible.

Chris

Thanks Chris for the explanation.

So I’m a retired aircraft mechanic and we safety wired or cutter pin EVERY bolt to prevent them from backing out. I was wondering if the crank bolt when used with CBC could use a cutter pin and the six smaller bolts could be safety wired for additional measures?

[Chris@VargasTurboTech]

I'm familiar with the aero industry and my condolences for all that lockwire I bet you did haha. In this application, I wouldn't bother. Blue locktite on the perimeter bolts is a good idea and sufficient to stop anything from coming undone.

[MR_X]

Originally Posted by Chris@VargasTurboTech

I'm familiar with the aero industry and my condolences for all that lockwire I bet you did haha. In this application, I wouldn't bother. Blue locktite on the perimeter bolts is a good idea and sufficient to stop anything from coming undone.

Copy RED Locktite...got it.

[Chris@VargasTurboTech]

Originally Posted by MJ6

Has anyone mathematically inclined attempted to determine exactly what the friction coefficient is for the friction disks given the clamping load provided by the crank bolt?

I'm no mechanical engineer, but I'd assume that given a known clamping force and friction coefficient, one should be able to determine the load required to overcome the torque capacity of the stock crank hub.

If clutch manufacturers are able to state clamp load forces which will hold up to xxx amount of torque/hp, it's not infeasible to say that the same couldn't be done here to determine at what power levels you become a higher risk. Without solid numbers to support it, stating that it "could happen" if you only have the crank bolt capture installed is anecdotal at best.

To be clear, there's no doubt in my mind that by splining or pinning the crank hub you provide a more permanent fix, but without definitive figures I find it difficult to justify spending an additional $3k plus over just installing a CBC. It has nothing to do with being cheap either, it's the same premise as to why you wouldn't upgrade your clutch to one rated to hold 800+ torque when you're only running at stock power levels: it's not necessary. Until we know how much power it takes to overcome the friction washers, the answer to what level of a solution is actually needed is (to me at least) nebulous.

Failures seem to vary with driving styles, power, mileage and habits. Remember there are 2 major causes of slipped crank hub, but either one (or both) land in you in the same place, and it's tricky to tell after the fact. Would be hard to put a torque go/no go number on it. If you believe the stock hub by itself when torqued properly is sufficient for your goals (i.e. stock power or close to it) then perhaps a CBC only reduces risk enough for you to justify the cost/benefit ratio, as this doesn't do anything to clamping force except help preserve it via not letting the crank bolt vibe loose and it's very inexpensive.

We have seen CBC only spins, they are more rare but depends on the build. The data is messy and changing; people tend to add mods with time, turn power up, add turbos, meth injection, etc. which complicates it. If you drive for 40k miles bone stock and put a tune on it and spin 500 miles later, would you expect the same car brand new to spin 500 miles in with that same tune? I don't have an answer to that but I suspect not.

Generally there is a spectrum from stock to heavily modded where you see increased incidents of slips with increased power output, but the few variables in play make it a little more murky to easily draw a line in the sand. Want to run upgraded turbos on E85 and push things? That's easy... do the full upgrade. Stock and under warranty? That's also easy, CBC only or nothing and if things slip make BMW pay. It's the in-between that needs consideration. You all know what I say the complete solution is.


Chris

[MisterF80M3]

Originally Posted by Chris@VargasTurboTech

Failures seem to vary with driving styles, power, mileage and habits. Remember there are 2 major causes of slipped crank hub, but either one (or both) land in you in the same place, and it's tricky to tell after the fact. Would be hard to put a torque go/no go number on it. If you believe the stock hub by itself when torqued properly is sufficient for your goals (i.e. stock power or close to it) then perhaps a CBC only reduces risk enough for you to justify the cost/benefit ratio, as this doesn't do anything to clamping force except help preserve it via not letting the crank bolt vibe loose and it's very inexpensive.

We have seen CBC only spins, they are more rare but depends on the build. The data is messy and changing; people tend to add mods with time, turn power up, add turbos, meth injection, etc. which complicates it. If you drive for 40k miles bone stock and put a tune on it and spin 500 miles later, would you expect the same car brand new to spin 500 miles in with that same tune? I don't have an answer to that but I suspect not.

Generally there is a spectrum from stock to heavily modded where you see increased incidents of slips with increased power output, but the few variables in play make it a little more murky to easily draw a line in the sand. Want to run upgraded turbos on E85 and push things? That's easy... do the full upgrade. Stock and under warranty? That's also easy, CBC only or nothing and if things slip make BMW pay. It's the in-between that needs consideration. You all know what I say the complete solution is.


Chris

Why do you still continue to spread lies? Where is the evidence of someone spinning their hub with CBC only? "I heard from a friend" or "I don't know the details" doesn't count. The only people that spun their hub is with your spline lock and CBC installed. A lot of people are still waiting for an explanation of why you blocked a customer for inquiring about warranty after spinning their hub with a VTT spline lock installed.

[ILoveCugars]

There have been multiple cars spin with just a CBC.

There was one posted today one of large F80 FB pages, 6mt, Ps2, 93oct tune, 550whp with spun hub.