FLC63s

Well, when I turn the exhaust OFF, it doesn't rattle, so it's definitely not detached.

But sorry if I stepped on toes if posting in the wrong thread.

playalistic

Hey, no problem, I wasn't trying to police the thread. I'm dropping mine into the local MB dealer to see if they'll replace this part. Fingers crossed.

sabre1978

Hi all - just to add a comment to this - I had this very same issue 3 years ago and posted this on MBWorld - I have a MY16 C63S. After taking my car into the dealer, the engineer came for a test drive - accepted that the metallic rattle under load, when valve flaps are open - was not right. This did take 2 visits before they accepted that there was an issue.

They ordered a new exhaust part and had this fitted. This resolved my issue for about 12 months. Then the metallic rattle came back again. I took the car back to the dealer - this was about 1 year ago now.

They said that there was a design fault with that centre piece exhaust that housed the exhaust flaps (basically its the flaps bouncing open/closed under load creating the metallic rattle) and that they had redesigned this on later models. They replaced my piece with the newer version and it has been completely perfect since. Even though it is only a year since the new part I have complete faith its now resolved.

It also has more overrun pops and bangs since that newer part was fitted.

Hope this helps someone.

Hyperion728

Have this exact problem in my brand new 2019 C63s coupe. I recently did a cat delete but since I was running it in I didn't really notice the sound prior.
It is a tinny rattle at 2500-3000rpm both on acceleration and over-run. Hate it! Present in Sport Plus mode only.

I am worried MB will try to get out of fixing it on the basis of the cat delete.
It makes the car sound like a clapped out 350 Chev with sticky lifters.
So is the consensus that it is the valve in the H pipe?

untamedd

yeah and like you i had a sec cat delete because of which the dealer refused to fix it.

The rattle was driving me nuts so i just took out that valve and replaced it with a straight pipe and no more rattles.

Hyperion728

This makes sense as the sound is occurring when the valves are open or partially open. Installing the AWE simulator is not going to help the noise then as it will simply hold the valve open.
The only solution to this issue is to get MB to replace the valve or to cut it out all together (which is what I may have to end up doing).

untamedd

you cant replace the valve. Have to spend around 3k for a new exhaust lol

Hyperion728

I am wondering whether it is when the valve in the H pipe is partially open as full throttle the noise goes away.
Looks like I'll be heading down the H pipe valve removal then as well. I probably won't need an AWE device to stop codes as I will be getting a custom tune and believe they can simply turn any error codes off.

Hyperion728

Yours sounds like it was pretty severe, revving mine I can't reproduce it like that. Only happens when under some load.

heligarret

So my car developed this rattle. I took it to the Dealer and they "Lubricated the valve". Picked up the car and drove out the drive way and the noise was worse!!! They took the car back and after 2 weeks apparently replaced the exhaust. They had the car for a total of 3 weeks. Guess what the noise is still there. I will take it back next week but I have no idea what they will do next!!!

amgsin

I got mine fixed by twisting the spring that opens the valve one extra time!!!! Hardly ever heard it again.
Good luck

Hyperion728

Update to my rattle on my MY19. This has now been fixed by my exhaust shop by taking out the spring to the flap mechanism on the H pipe, welding the flap open and having the flap motor free spin. Has not thrown a code either. However, it is very clear that AMG use that valve to tune the sound and I can confirm that the car definitely does not sounds as good, especially on closed throttle, it’s not subtle, it is quite noticeable. The H pipe valve closed or partially closed is obviously doing something very positive for the sound of the exhaust. H pipes and X pipes tend to make exhausts sound more ‘smooth’ and this is what it has done but the rorty, aggressive sound has been lessened, even with a secondary cat delete. Next step may be to try some downpipes but I wonder whether it is worth trying the valve closed permanently?

Syndicate949

Does the car sound better/worse after your solution? Are you experiencing over run? Mine is sooo annoying I am willing to do anything and if it doesn't work I'm just gonna buy an axhaust.... AWE or FI I guess...suggestion welcome in this regard

Syndicate949

Does the car sound better/worse after your solution? Are you experiencing over run? Mine is sooo annoying I am willing to do anything and if it doesn't work I'm just gonna buy an axhaust.... AWE or FI I guess...suggestion welcome in this regard

Hyperion728

By “overrun” I mean closed throttle after accelerating does not sound as good with the H pipe kept open all the time. Fixed my rattle, though.

The exhaust is less deep and rorty with the valve open permanently, this seems to make sense from my research.
From my reading, an X or H pipe on a turbo car is not all that important, very different story on a naturally aspirated engine where it aids in scavenging.

I believe the H pipe OPEN on the C63s is actually being used to quieten the car down in, say, comfort mode, but they CLOSE it in Sport+ mode in some situations (it may be complex) to get more sound since the scavenging effect on a turbo car is not particularly important. But hey, I really don’t know but suspect there is a lot more going on with that valve than simple open or closed.

I wish there was an automotive engineer who could give me a definitive answer on this

JWreck

Except multiple people have confirmed that it is opened when the exhaust button is pressed or in sport/+/race.

Hyperion728

Who has confirmed this? Do they have the H pipe throttle position, torque maps which shows this? Everyone is guessing here unless they can see the valve. I have my H pipe valve held constantly open and I am telling you that the exhaust is quieter, especially when on trailing throttle. I have a before and after comparison right here in my driveway. I suspect there is much more going on with this valve than simple open or closed and it may even be opening to make the exhaust quieter, not louder. This is what many OEM do to quieten cars down. There are YouTube clips of vehicles with and without an X pipe (which has a similar effect) and they are louder without an X pipe.

The H pipe valve has a different effect from holding open the muffler valves, which will be louder when open.

untamedd

thats only true for the muffler valves.

the H pipe valve is not controlled via a button. It open/closes automatically based on your driving.

playalistic

I had the same problem on my 2017. When I fitted a valve simulator to the H-pipe I got exactly the same result as you - it was nowhere near as deep sounding as before so I removed it and suffered the noise for a bit longer since I was upgrading to a 2019 anyway. Thankfully my 2019 hasn't made the same rattle (yet at least since I'm certain my 2017 didn't do it right off the bat)

untamedd

i removed the H pipe valve as well and did notice that the car was a little less throaty under full load however I feel as if in the lower revs it is actually more deep. Did you notice that or is that just me?

as far as a solution goes, i doubt downpipes would solve it since from what ive heard downpipes kinda make the car more raspy than throaty.

for that throaty, gargling sound your best bet may be an aftermarket exhaust like the AWE Track.

Also, if you believe on a turbo car an X or H pipe isnt necessary then you could also go to aky exhaust shop and just replace that H section with straight pipes?

munis

He would not gain anything by replacing it with a straight pipe as his valve is completely open anyway as he has weld it open. Now have Hyperion considered the fact that may be your exhaust guy is a noob and instead welded it shut instead of open? If not, how are you sure or able to verify?

Encore818

My car had been in the shop for almost a month getting some body and paintwork done.

I have an asr module and I know from mercedes me Connect that the car was unlocked almost the entire time. From what I hear when I unlock the car, I believe that means the exhausts were being help open all that time.

When I got the car back a couple days ago I noticed a noise that only comes for about a second under heavy load. It comes when the g-force is at its peak, literally the first second after I step on the gas.

To me, it sounds similar to the sound of someone securing a ziptie. But I wonder now if its the same sound everyone in this thread is experiencing.

Any advice? I really don’t want to be without my car for so long again just after getting it back.

I’d atleast like to help them out with what the issue is so the car isn’t in for as long.

Thanks!

untamedd

I meant just remove that section altogether so in essence there would be no H pipe in the middle of the entire exhaust. It would be an experiment at best since Im not sure what kind of effect it would have on the sound.,

Hyperion728

The exhaust shop are one of the most experienced in my city, although they don’t know a great deal about the effect the H pipe has.They say the valve has been carefully spot welded open and that it will be a simple job to do the same with it in the other direction or any way in between. I am trying that on Monday and will report back to the thread. Will be a very interesting experiment. Advantage of doing it this way, instead of removing the valve all together is that it looks completely stock underneath (other than the secondary cat delete I guess). I’ll get under it and check it out on Monday.

From my research, the H pipe is solely to manage sound in our application (when open, it decreases noise levels *not* increase as I and others have found). Big X pipes will do the same and are also important for exhaust scavenging on a naturally aspirated twin bank engine such as a V8.
On a turbocharged engine, the job of the exhaust has been done before the turbine compressors, after the turbos you just want the gas out. This is probably why the turbo AMGs have an H pipe and not an X pipe since a little H pipe isn’t going to do a great deal. It is simply to manage sound but not in the way that many think, it is there to decrease sound with valve open and increase sound with it closed.

untamedd

i thought the H valve opens when the engine is under load but didnt think it made it quieter when open.

i guess you came to that conclusion because with the valve open youve lost the throaty tone?

interest experiment regardless. Very curious to see what you think after because i might follow too if tje results are good.

have you thought of doing a muffler delete? Kinda like the AWE Track.