[billypopo]

Curious to know what was the outcome? I’m hearing that same 0.5-1sec weird ‘grinding’ metallic sound on every pull when initial rpm is low (say below 2250 or so). 2021 dct m2c

[Piets94]

I used to think it was rattling exhaust valves, every time around 1900rpm on acceleration only (DCT). Unplugged the exhaust valves and made no difference to this sound (although the exhaust sounds nicer ).

I believe mine is turbo wastegate rattle. Seems to be a common S55 trait.

[MadBimmeRad]

Any other 6MTs with similar sounds?

[mfarrzhp]

I forgot to have service check it out, and I can't remember the last time I heard it.

It's more of a metallic rattle than grind. I don't think it's waste gate rattle, which I had on my old 135i. That was much more pronounced and was always there. This is definitely intermittent.

I'll listen for it next time I take the car out.

[MinionM3]

I have the exact same thing - possibly always been there but just started to notice it about 3 weeks ago. I am 6MT as well.

Metallic rattle, sounds like it's coming from directly under the car IMO, it is at very low RPM, like first gear and gently pulling away, or a lazy 1-2, and not giving hard throttle, hear it in 2nd as well.

It happens for a second and is gone.

Seeing the heat shield comments makes me believe that's what it is - I definitely do not think it's coming from under the hood or at the very back of the car - really sounds to me like it's right under me in the middle of the car.

[romes4rs]

Those of you that hear this sound, do you also have Auto Solutions SSK? Might have this rattle too and it only occurred after install. Naturally thought is was a heat shield as well.

[Jimjamz]

It's not clear to me if you're referring to an ongoing noise or a sudden one? If it's a brief one and sounds like a light metallic tap at low rpm, some here (myself included) have noted the exhaust valves opening and closing as you release your throttle - most notably when the efficient engine throttle setting is activated.

[TwoTwentyBlue]

Based on the descriptions here, I'm thinking this is similar to what I captured in this video.

https://youtube.com/shorts/L3NLo4_3Ycs?feature=share

Another forum member in the UK was experiencing the same thing on his M2 CS and his dealer ultimately determined this was being caused by a scored camshaft after several weeks in their shop and multiple consultations with BMW UK and BMW HQ.

I shared this info with my dealer and multiple videos like the one linked above but unfortunately have been told multiple times they can't replicate the noise.

I've continued to drive my car with the noise coming up intermittently and choosing not to worry about it since I've tried to get it resolved with no luck so far. This has also made me consider an extended service contract just in case it does escalate into a bigger problem down the road but I haven't pulled the trigger yet.

For those wondering, my M2 CS is stock with a DCT and windows closed during this recording.

[mfarrzhp]

Originally Posted by TwoTwentyBlue

Based on the descriptions here, I'm thinking this is similar to what I captured in this video.

https://youtube.com/shorts/L3NLo4_3Ycs?feature=share

Another forum member in the UK was experiencing the same thing on his M2 CS and his dealer ultimately determined this was being caused by a scored camshaft after several weeks in their shop and multiple consultations with BMW UK and BMW HQ.

I shared this info with my dealer and multiple videos like the one linked above but unfortunately have been told multiple times they can't replicate the noise.

I've continued to drive my car with the noise coming up intermittently and choosing not to worry about it since I've tried to get it resolved with no luck so far. This has also made me consider an extended service contract just in case it does escalate into a bigger problem down the road but I haven't pulled the trigger yet.

For those wondering, my M2 CS is stock with a DCT and windows closed during this recording.

I think this is different than mine. Mine is 1 second tops and I think a higher frequency rattle, coming from underneath towards the rear. I've never noticed it with the windows up, but that just could be because I listen to music most of the time. I'll try to grab a video this weekend.

It is similar, but mine is even lower RPMs and is gone by 1500 RPMs or so. It's intermittent, or at least I only notice it intermittently.

My car is stock other than H&R springs.

[Jimjamz]

Originally Posted by TwoTwentyBlue

Based on the descriptions here, I'm thinking this is similar to what I captured in this video.

https://youtube.com/shorts/L3NLo4_3Ycs?feature=share

Another forum member in the UK was experiencing the same thing on his M2 CS and his dealer ultimately determined this was being caused by a scored camshaft after several weeks in their shop and multiple consultations with BMW UK and BMW HQ.

I shared this info with my dealer and multiple videos like the one linked above but unfortunately have been told multiple times they can't replicate the noise.

I've continued to drive my car with the noise coming up intermittently and choosing not to worry about it since I've tried to get it resolved with no luck so far. This has also made me consider an extended service contract just in case it does escalate into a bigger problem down the road but I haven't pulled the trigger yet.

For those wondering, my M2 CS is stock with a DCT and windows closed during this recording.

Ok that's nothing like what I was describing. Sounds like a gerbil in the glove compartment.

[billypopo]

Originally Posted by mfarrzhp

I think this is different than mine. Mine is 1 second tops and I think a higher frequency rattle, coming from underneath towards the rear. I've never noticed it with the windows up, but that just could be because I listen to music most of the time. I'll try to grab a video this weekend.

It is similar, but mine is even lower RPMs and is gone by 1500 RPMs or so. It's intermittent, or at least I only notice it intermittently.

My car is stock other than H&R springs.

This sounds more like mine. I tried getting a video of it, we can hear it slightly a few times :

https://youtube.com/shorts/gGP0Tbv-fD8?feature=share

https://youtube.com/shorts/ddk-ihBVpDo?feature=share

[MadBimmeRad]

Originally Posted by TwoTwentyBlue

Based on the descriptions here, I'm thinking this is similar to what I captured in this video.

https://youtube.com/shorts/L3NLo4_3Ycs?feature=share

Another forum member in the UK was experiencing the same thing on his M2 CS and his dealer ultimately determined this was being caused by a scored camshaft after several weeks in their shop and multiple consultations with BMW UK and BMW HQ.

I shared this info with my dealer and multiple videos like the one linked above but unfortunately have been told multiple times they can't replicate the noise.

I've continued to drive my car with the noise coming up intermittently and choosing not to worry about it since I've tried to get it resolved with no luck so far. This has also made me consider an extended service contract just in case it does escalate into a bigger problem down the road but I haven't pulled the trigger yet.

For those wondering, my M2 CS is stock with a DCT and windows closed during this recording.

This happens when I try to play your vid

[mfarrzhp]

Originally Posted by billypopo

This sounds more like mine. I tried getting a video of it, we can hear it slightly a few times :

https://youtube.com/shorts/gGP0Tbv-fD8?feature=share

https://youtube.com/shorts/ddk-ihBVpDo?feature=share

It's hard to discern from the video clip, but I think my issue was the same as yours.

It gave me a reason to take the CS out this morning. I tried to replicate and record the sound, but it didn't happen. It's been months since I've noticed it now. It either went away after a couple thousand miles or it's mild enough that it has to be the right RPM frequency and driving with the right surroundings to have the noise bounce back to my ear. That makes me think it's nothing internal, but rather something that is or was a bit loose, like the heat shield.

[GM2CS]

I've been running this fuel (101 Octane) for a few weeks. The CS motor seems to like it. If you're in So.Cal there is probably a 76 station nearby that has it

[medphysdave]

That would be really interesting if there was a "hidden" map for higher octane fuel.

[billypopo]

Just found a post with a better video in which we hear the exact sound I get

https://www.bimmerpost.com/forums/sh...php?p=25304937

[Tornado1M]

This does make a difference….

https://www.pure-gas.org

[Piets94]

Originally Posted by billypopo

Just found a post with a better video in which we hear the exact sound I get

https://www.bimmerpost.com/forums/sh...php?p=25304937

Yeah, that sounds like mine too. Wastegate rattle. Been there since new, any driving mode (though less noticeable in efficient).

[sm2key]

hello everyone i have a vibration/fast rattle, like a metal on metal sound like a loose bolt, coming from (not sure) engine/passenger side underneath (lhd)

Only happens when i rev from a stand still in neutral, doesn't matter how high i rev, when the rpms drop at around 1800/1500 i hear this noise, any guesses? already checked for shield but didn't find anything

TIA

[MDuckie]

Originally Posted by billypopo

This sounds more like mine. I tried getting a video of it, we can hear it slightly a few times :

https://youtube.com/shorts/gGP0Tbv-fD8?feature=share

https://youtube.com/shorts/ddk-ihBVpDo?feature=share

Holy shit. I’ve been having this exact issue with my car for the past year. I have yet, until now, found anyone else with this sound and the mechanic I brought it to (who installed my exhaust) blamed it on something in front of the link pipe. I started noticing it after having the Akra Evo setup installed. Did you ever figure this noise out?

[billypopo]

Originally Posted by MDuckie

Holy shit. I’ve been having this exact issue with my car for the past year. I have yet, until now, found anyone else with this sound and the mechanic I brought it to (who installed my exhaust) blamed it on something in front of the link pipe. I started noticing it after having the Akra Evo setup installed. Did you ever figure this noise out?

I did. It was the connection between the DP and midpipe. There are crush washers in there. Replace everything with new and you should be ok.