Why isn't the CBC enough

[LATTES]

Originally Posted by ssgm1x

Stock f80/f82 with just a CBC will suffice.....

How about light stage2 tune

[fknlo]

Originally Posted by parabmw

How easy is the CBC only install?
1 hr? Minimal removal of parts like radiator?

I had a shop do it while they were changing my oil. I'm capable of doing that work but I'm lazy as hell. It took them about 4 hours. I've seen that time frame mentioned from people that have done it themselves as well. They thought their time might have been off but they apparently deal with the supplier I bought it from and they said that it wasn't uncommon, even for a shop. I was the first one they'd done and I'd imagine that anyone that does it regularly could knock it out faster.

[Twistm4]

It's such a subjective question. As what is considered the acceptable "risk" percentage that would apply to everyone? 1 percent chance? 5 percent chance? Who knows.

All I know is there are hundreds of f8x owners on stage 2 flashes with SCH. It totally depends on what side of this equation you are on... if a 4,000$ service job is worth preventing a tiny, tiny, chance at gambling a 7-10k motor *used then get it done. For a lot of us, it is not. In my perception, with my goals, with my view on the matter, anything less than a turbo upgrade and e85 the CBC is enough prevention when calculated with the risk of slipping or breaking the friction plate on stock turbo power.

Car has seen hundreds of 40-160mph roll races, at least 100 launch control launches for $ on radials and has not skipped a beat. However treat the DCT like a manual, never lug the engine nor use the kickdown EVER. No downshifts that would put the engine into peak torque range in full power gears (4th and up, 3500+ rpm). With that being said I have heard horror stories of guys running base maps for years with no issue then as soon as they went to e50 custom tune, itll slip after the first couple of pulls. The CBC just prevents the most common form of failure.

TBH a stock car or stage 2 pump gas f8x paying 4+k$ to pin it and then stay at p**sy power levels is whats ludicrous to me. If you're going to pay that much to do it you might as well let the s55 do what its truly capable of afterwards.

[TopJimmy]

The problem with doing only the CBC is that you don't know the status of your crank bolt (stretched, mis-torqued, slightly slipped, or correct). I asked Kies about doing "the German Solution" of an extra quarter turn of the crank bolt and then the CBC. They said they don't do the over-torque job. It's just as much work and you can still spin the friction disc. I'm already at 550 crank HP...

Many things come into play when deciding on the Hub Fix or not. My factor is I'd rather spend the money and know I can drive how I like without risk/shame of being stuck on the highway some day. I can also tell the next owner that the "weak link" is handled, and there's a Hub+CBC in there (CBC only adds $100 to the job).

Others may decide to ride the edge, wait till it happens, or hope they don't have it at all. I'd rather have dependability now and for future potential mods.

-TJ

[cheveux]

Originally Posted by TopJimmy

The problem with doing only the CBC is that you don't know the status of your crank bolt (stretched, mis-torqued, slightly slipped, or correct)...

This is true and the only thing that could prevent cbc from working, but even so I never found any report of a cbc failing. Even the brands that sell the keyed solutions or splines solutions say they know situations of cbc failures, but they never showed it.

In my opinion, the cbc is sufficient for those who do not abuse the car, that do not have an aggressive driving style that is known to be mechanically risky, that is, no kickdown, avoid downshift in the third mode of the dct, or usage of launch control.

I have a stage 2 with 545hp and 680tq and cbc installed. The car is powerfull but I don't do anything I wrote above. Yes, i baby my car, but because that is my driving style. I don't need to show off, nor do I want to. I use the M4 for trips like a GT car. Obviously, I also enjoy the power of the car, but no kickdown or launch control. If I need to downshift, I do it manually and I am careful to make a linear acceleration and only stronger at higher speeds/rpms where the turbos already passed their boost peak, avoiding hard torque changes on the dct or the crankhub.
Dropping the accelerator suddenly in high gear can also be a problem. Everything can put too much force/torque on the central screw.

I think this problem happens 50% due to the bad tightening of the factory central screw, but the other 50% of the driving. The first 50% seem to me solved with the cbc. The other 50% is up to us as drivers. Even the friction disc slides due to the loosening of the screw, in my opinion.

And if it were not so, the cbc was not so popular in Europe.
Only Pure Turbos advise installing the gintani crank hub for obvious reasons.

[horsepower_and_hounds]

So when you do the CBC you you attempt to verify torque on the crank bolt?

[cheveux]

Originally Posted by horsepower_and_hounds

So when you do the CBC you you attempt to verify torque on the crank bolt?

No, that's impossible. The crank bolt is one time use only and it stretches. you can't torque it after the first time. Even if you could, you had to lock all the timing chain system.

[horsepower_and_hounds]

Originally Posted by cheveux

No, that's impossible. The crank bolt is one time use only and it stretches. you can't torque it after the first time. Even if you could, you had to lock all the timing chain system.

Thanks for the info......CBC + Hope + Prayer

[swifty]

Originally Posted by cheveux

This is true and the only thing that could prevent cbc from working, but even so I never found any report of a cbc failing. Even the brands that sell the keyed solutions or splines solutions say they know situations of cbc failures, but they never showed it.

In my opinion, the cbc is sufficient for those who do not abuse the car, that do not have an aggressive driving style that is known to be mechanically risky, that is, no kickdown, avoid downshift in the third mode of the dct, or usage of launch control.

I have a stage 2 with 545hp and 680tq and cbc installed. The car is powerfull but I don't do anything I wrote above. Yes, i baby my car, but because that is my driving style. I don't need to show off, nor do I want to. I use the M4 for trips like a GT car. Obviously, I also enjoy the power of the car, but no kickdown or launch control. If I need to downshift, I do it manually and I am careful to make a linear acceleration and only stronger at higher speeds/rpms where the turbos already passed their boost peak, avoiding hard torque changes on the dct or the crankhub.
Dropping the accelerator suddenly in high gear can also be a problem. Everything can put too much force/torque on the central screw.

I think this problem happens 50% due to the bad tightening of the factory central screw, but the other 50% of the driving. The first 50% seem to me solved with the cbc. The other 50% is up to us as drivers. Even the friction disc slides due to the loosening of the screw, in my opinion.

And if it were not so, the cbc was not so popular in Europe.
Only Pure Turbos advise installing the gintani crank hub for obvious reasons.

Many in Europe do have CBC installed if tuned.

Check Litchfield who actually created their own tool to install their crank hub solution.

However even Litchfield suggests just doing CBC if the crank hasn't spun yet. I spoke to them when I had my M3 tuned and they didn't feel it was necessary to do both unless the crank did spin. Also their CBC is different than the others on the market.

Unfortunately they only sell their CBC overseas and not their full solution due to the special tool and to prevent others from copying their kit.

[RevNev]

Originally Posted by cheveux

No, that's impossible. The crank bolt is one time use only and it stretches. you can't torque it after the first time. Even if you could, you had to lock all the timing chain system.

If you lock the crank with a bar bolted to the hub (where the CBC bolts on) and resting on the ground, torqueing the crank bolt an extra 1/4 of a turn will spin the hub and shift the cam timing?

Loosening the bolt to "re-torque" it would require timing verification and lock, but adding more tension to a pre-torqued bolt shouldn't shift the cam timing, or essentially "spin the crank hub" by adding bolt tension.

What we don't know, is whether the crank bolt was torqued to spec in the first place, or perhaps they need 360 degs of rotation after the initial torque instead of 270. Maybe 270 degs is on the cusp of tension required to prevent a hub spin.

Obviously the guys fitting CBC's are aware of the problem and seems like a fix because they're not abusing their engines to the extent where a spun hub typically happens.

Nevertheless, why hasn't BMW at least changed the crank hub design on engines destined for GT4 race cars? They don't want cars retiring from races with spun crank hubs, yet the GT4 retains the same road car engine and timing components. The GT4 engines cop a severe thrashing for sustained periods of time along with the associated driver errors without BMW recognising a crank hub problem and applying a remedy for these engines. It's common to find upgraded components in race car versions like the GT4 runs different drive shafts than the road car which probably break on slick tyres, but there's no crank hub differences so why not if it's a major design fault?

[AllNatty]

Just spun my hub with only CBC installed :/

[yjypm]

Originally Posted by RidduLs

Just spun my hub with only CBC installed :/

Any more details? Power level? Scenario?

[AllNatty]

Originally Posted by yjypm

Any more details? Power level? Scenario?

Was ripping through gears on back roads. Saw the drivetrain malfunction come on and immediately shifted to neutral. When I got to a stop, noticed the car was idling pretty rough. Turned it off and will have it towed tomorrow. FBO and custom 93 tune.

[yjypm]

Originally Posted by RidduLs

Was ripping through gears on back roads. Saw the drivetrain malfunction come on and immediately shifted to neutral. When I got to a stop, noticed the car was idling pretty rough. Turned it off and will have it towed tomorrow. FBO and custom 93 tune.

Hopefully just your spark plugs or something else. Best wishes!

[maddmatth]

Originally Posted by RevNev

Nevertheless, why hasn't BMW at least changed the crank hub design on engines destined for GT4 race cars? They don't want cars retiring from races with spun crank hubs, yet the GT4 retains the same road car engine and timing components. The GT4 engines cop a severe thrashing for sustained periods of time along with the associated driver errors without BMW recognising a crank hub problem and applying a remedy for these engines. It's common to find upgraded components in race car versions like the GT4 runs different drive shafts than the road car which probably break on slick tyres, but there's no crank hub differences so why not if it's a major design fault?

From a quick google... the GT4 has the same power levels as the base M4 at 425HP.

I don't think we are concerned about this issue at stock power levels? BMW are going to design the engine to perform within their specification, what happens when people tune them aggressively and slap on upgraded turbos is not their concern.

Consider the most aggressive tune BMW offers for the S55 is on the GTS, they added water injection and additional oil capacity with 500hp.

Meanwhile aftermarket tuners happily give you more power with a software flash, and people think this is going to come easy and trouble free
Big power levels require big money... you gotta pay to play. There's a reason you can't get more than 500hp out of an S55 and still have a warranty

[FreeDarko]

Originally Posted by RidduLs

Just spun my hub with only CBC installed :/

This has to be the first? Have you had any engine issues prior to installing the CBC?

[AllNatty]

Originally Posted by FreeDarko

This has to be the first? Have you had any engine issues prior to installing the CBC?

Originally Posted by FreeDarko

This has to be the first? Have you had any engine issues prior to installing the CBC?

Nope. Haven't had any issues with it at all until now. 2016 DCT with 43k miles

[FreeDarko]

Originally Posted by RidduLs

Nope. Haven't had any issues with it at all until now. 2016 DCT with 43k miles

Can you advise which CBC was used?

[Twistm4]

Originally Posted by RidduLs

Nope. Haven't had any issues with it at all until now. 2016 DCT with 43k miles

Lets wait until this is verified by your tech. Please get a screenshot of the codes if possible! Just because the car goes into malf. protective mode doesn't necessarily mean the worst case scenario. Cheer up man hopefully its something small and stupid!

[Ejones4541]

Originally Posted by RoadRunner///M

Read your other thread re your experience and it doesn't confirm that you spun yours yet. In fact you simply had drivetrain malfunction with rough idle, which could be a number of issues, not necessarily SCH.
Given this is such a hot subject at the moment, perhaps wait to confirm what is wrong with your car before throwing fuel on the fire

+1

[Jbonly21]

+2 , don't everyone have a scanner? I have one in each of my cars, I don't understand why would you start a thread with out at least checking the codes first , or tow your car to a shop with out investigating first. I just think its not very helpful when all we read is, spun my crank, took it to ????? Now its fix. Nobody never really knows what happened. Just my 2 cent.

[RevNev]

Originally Posted by maddmatth

From a quick google... the GT4 has the same power levels as the base M4 at 425HP.

I don't think we are concerned about this issue at stock power levels? BMW are going to design the engine to perform within their specification, what happens when people tune them aggressively and slap on upgraded turbos is not their concern.

Consider the most aggressive tune BMW offers for the S55 is on the GTS, they added water injection and additional oil capacity with 500hp.

The M4 GT4's base power level is quoted the same as a stock M4, but there's 5 plug in power sticks that increases horsepower well over 500 but the point is, they're subject to extreme abuse for extended periods of time and vulnerable to driver error in a racing environment.. It's said that some stock engines have spun the crank hub yet it doesn't seem to be an issue for the GT4, why is that?

BMW did make changes to the GTS. Water injection to accommodate pump fuels of insufficient octane and extra oil to prevent oil surge from the additional G forces the GTS chassis can generate on a race track. But they didn't change the crank hub and timing gear arrangement on the GT4.