Cracked stock muffler

[RichBunch2]

Just a heads up to those with the stock GTS titanium muffler. I noticed an exhaust rattle when in eco mode (only time muffler is used). The muffler was cracked. There also was a small crack forming on the bottom side but I neglected to snap a pic. It's under warranty so it's going to be replaced. When talking with the tech he said it was the third he's seen and there aren't many GTS's in the small town I live in.

[LOW4LYF]

Wow... first MPE, now GTS...

[Studntloan]

seems like things like cracking on the gts

[Bluer2]

That is because the GTS muffler is the same as the MPE. At least on the exterior. There is a reason BMW added structural support braces to the MPE.

[Day Laborer]

Originally Posted by Studntloan

seems like things like cracking on the gts

Ya'll got any more of them ?

[delfunk]

Originally Posted by Day Laborer

Ya'll got any more of them ?

Oh wow first the suspension and now the exhaust? 🤦bravo BMW!

[RichBunch2]

Not to add fuel to the fire, but my car is in the shop now for a slipped crank hub. I have less of a problem with a part failure like the muffler and front upright than I do with the crank hub. I view the crank hub as a design failure. I just don't know why they didn't key the hub and or sprockets, especially on a turbo car.

[CanAutM3]

Originally Posted by LOW4LYF

Wow... first MPE, now GTS...

Its basically the same exhaust... so it's not surprising.

[M2driverWV]

Originally Posted by RichBunch2

Not to add fuel to the fire, but my car is in the shop now for a slipped crank hub. I have less of a problem with a part failure like the muffler and front upright than I do with the crank hub. I view the crank hub as a design failure. I just don't know why they didn't key the hub and or sprockets, especially on a turbo car.

What tune were you running? How many miles on the engine when this happened?

[Bluer2]

wow first time hearing a GTS slipped the crank hub. also interested to know if you are stock or tuned on BM3?

[RichBunch2]

The previous owner installed Active Autowerke's downpipe and tune. I had Active do a conservative tune and also some throttle mapping things.
The car has ~5000 miles on it.

There is more to the crank hub slipping than just a tune.

The slip happened Mar 1 at an open lapping day. It was raining in the morning and then was drying out. Wet spots, damp spots, and dry. In addition, I ran low on fuel twice in the morning. Low enough that the car started stuttering. The first time running low on fuel the car threw the drive train fault. Came in, refueled and added water. Code gone. The second time running low on fuel, same code. Came in, added fuel and water. Code remained and went into limp home mode. I was running Toyo R888R, so not crazy sticky but definitely stickier than PSC2's.

The difference in grip levels with the rain and drying track combined with the stuttering from low fuel combined with the modest power increases from the tune, in my opinion, caused the crank hub slip. Not necessarily one thing but definitely odd that the light only came on when running out of fuel. The BMW techs and independent shop I use all agree.

I did not file a warranty claim. Didn't even try. I didn't see the point since I had no intention of going back with the stock setup (friction, no pin of any type). I also didn't want to fight city hall only for them to say the car would have been fine if it wasn't tuned. While the BMW answer is the "tune", I feel that is pretty short-cited on their part. I've talked with my local dealership and they have encountered this problem on tuned and not-tuned cars. I've read elsewhere on this forum stories of cars tuned and not-tuned with the problem. I suppose BMW has their reasons for not pinning the crank hub, which I'm sure I will never know.

The car is presently at my local dealership. I chose to use them because they did the very same repair last year. Local shops also do not have the fixtures to do the timing and I'd rather not be the one paying for those tools. The dealership has been more than accommodating and have given me what I felt like is a good deal on the price. I went with the Maximum PSI solution. Car should be done early this week.

The timing was only off at the cams which confirmed the hub slipping. Also, the timing was only very slightly off allowing VANOS to adjust within tolerance most of the time which is why the fault code would clear itself. I've heard other stories of the hub slipping more significantly and causing further damage.

I wanted to go with what the M4GT4 uses. I went to RealOEM and the GT4 has the exact same part listed. There is no way they are using the same, un-pinned, crank hub. Certainly not with Pirelli slicks. I tried calling a couple teams but it was the day after the World Challenge COTA race and i wasn't able to reach anyone. I needed to make a decision so I moved forward with the Maximum PSI solution.

These things happen and the car will be better once I'm done with it. I've learned over the years that if you think a car should be perfect and never have issues you are going to be sorely disappointed. Or you're not out enjoying the car to its fullest. The car is great otherwise. A blast to drive. Great to look at.

[CanAutM3]

I think folks underestimate the effect of a tune and the risk of spinning the crank hub. My understanding is that over-accelerating the engine beyond a certain threshhold is what causes the crank hub to spin. And the engine and DCT tunes have a direct impact on this. The crank hub does seem to be the weak point and I can only assume BMW designed it that way as a security failure point to prevent more catastrophic failures.

[RichBunch2]

Originally Posted by CanAutM3

I think folks underestimate the effect of a tune and the risk of spinning the crank hub. My understanding is that over-accelerating the engine beyond a certain threshhold is what causes the crank hub to spin. And the engine and DCT tunes have a direct impact on this. The crank hub does seem to be the weak point and I can only assume BMW designed it that way as a security failure point to prevent more catastrophic failures.

So would it then be your thoughts that the GT4 runs the same crank hub as the regular M4 and has no issues? Or have I extrapolated too much from your comment?

[///M///]

Originally Posted by CanAutM3

I think folks underestimate the effect of a tune and the risk of spinning the crank hub. My understanding is that over-accelerating the engine beyond a certain threshhold is what causes the crank hub to spin. And the engine and DCT tunes have a direct impact on this. The crank hub does seem to be the weak point and I can only assume BMW designed it that way as a security failure point to prevent more catastrophic failures.

Confused. You mean folks who increase redline via a tune or just the tune itself?
Is there much difference between your CS hub and a standard M3/4? If not then a standard hub should safely be able to run the stage 1 BM3 tune. Would you agree?

[allinon72]

Originally Posted by CanAutM3

The crank hub does seem to be the weak point and I can only assume BMW designed it that way as a security failure point to prevent more catastrophic failures.

A security failure point that has the potential to destroy the engine, designed on purpose? No way.

[nbennettksu]

Originally Posted by CanAutM3

I think folks underestimate the effect of a tune and the risk of spinning the crank hub. My understanding is that over-accelerating the engine beyond a certain threshhold is what causes the crank hub to spin. And the engine and DCT tunes have a direct impact on this. The crank hub does seem to be the weak point and I can only assume BMW designed it that way as a security failure point to prevent more catastrophic failures.

Exactly, it appears to be "fuse" like to prevent anything further.

[RichBunch2]

"Is there much difference between your CS hub and a standard M3/4? If not then a standard hub should safely be able to run the stage 1 BM3 tune. Would you agree?"

Not sure if you were talking about the hub I installed or what CanAutM3 was referring to...I'll answer for me

The Maximium PSI has to two pins that you drill into the snub of the crank. Then the first piece of the hub, either oil or cam sprocket can't remember which is first, has pins that go into the newly drilled holes. The second piece of the crank hub locks into the first with a couple indexing tabs, this piece has the second set of sprockets and hub. All gets bolted together. It's the pins that keep it from slipping.

The pinning of the crank hub is similar to what Porsche does on certain 911 motors. Not that they don't have their shortcomings, but it's the manufacturer that I have the most experience with

[///M///]

Originally Posted by RichBunch2

Not sure if you were talking about the hub I installed or what CanAutM3 was referring to...I'll answer for me

The Maximium PSI has to two pins that you drill into the snub of the crank. Then the first piece of the hub, either oil or cam sprocket can't remember which is first, has pins that go into the newly drilled holes. The second piece of the crank hub locks into the first with a couple indexing tabs, this piece has the second set of sprockets and hub. All gets bolted together. It's the pins that keep it from slipping.

The pinning of the crank hub is similar to what Porsche does on certain 911 motors. Not that they don't have their shortcomings, but it's the manufacturer that I have the most experience with

I was responding to CanAutm3 in reference to the stock CS hub vs a stock standard M3/4 hub. My point was that if a stock CS hub is the same as a stock standard m3/4 hub, the stage 1 tune on a standard F8X should not affect the hub as the added power is around the same as as a stock CS. Hope that makes sense.

[RichBunch2]

[/QUOTE]

"I was responding to CanAutm3 in reference to the stock CS hub vs a stock standard M3/4 hub. My point was that if a stock CS hub is the same as a stock standard m3/4 hub, the stage 1 tune on a standard F8X should not affect the hub as the added power is around the same as as a stock CS. Hope that makes sense."


Yes, makes sense.
Based on RealOEM, the M4GT4 has the exact same hub setup as the M4 (and in my case GTS as well).
Assuming that the GT4 teams have in fact not changed that setup, then I'd agree with your line of thinking.

[///M///]

Originally Posted by RichBunch2

Yes, makes sense.
Based on RealOEM, the M4GT4 has the exact same hub setup as the M4 (and in my case GTS as well).
Assuming that the GT4 teams have in fact not changed that setup, then I'd agree with your line of thinking.

Heads up. Your "quote" feature is not working when you reply. Just use the button at the bottom of the post.

[RichBunch2]

Originally Posted by ///M///

Heads up. Your "quote" feature is not working when you reply. Just use the button at the bottom of the post.

I know. I was trying to only quote part of your comments not the entire thing but i couldn't figure it out (didn't spend much time). Think I just got it. Sorry

[tom @ eas]

Please follow up on what replacement you're provided with. All MPEs we've seen get the v2 with added reinforcement brackets, curious to know if the same applies to GTS: