Hey fine folks - new member here. Looking forward to getting involved.

‘15 C63S sedan owner, 20k miles. The baffle/valve in the H-pipe started rattling horribly, which I understand is not completely uncommon.

However - it turns out a simple replacement of that valve wasn’t the real issue ... something in the linkage that opens and shuts the valve snapped, and it looks like a larger exhaust system replacement is in my future.

So since I’m gonna be up for the labor, feels like rather than going back to factory pipes, I should step it up to something more fun.

I’ve only just started researching, and I’m sure much of what I’m looking for is buried in these forums already (and I’ll be searching!), but thought I’d ask for some advice. Any of you in love with a particular aftermarket exhaust swap?

Budget is certainly not limitless, but I know what performance costs on these fantastic beasts. Also, I live in Texas where emissions are scrutinized a little bit, and I’m still under warranty for quite awhile longer, so definitely don’t want to invalidate it

Thanks everyone!

Option 1: no need for a full exhaust replacement. cut the H pipe with valve out and weld in a straight pipe with an AWE valve simulator to prevent a CEL.

Option2 : Replace full exhaust. I have AWE Track and its great but this is subjective and youre prob better off doing your homework since some people still like to maintain the valve functionality.

thanks for the response:

Re: option 1 - a straight pipe w the simulator suggests that it’s basically in ‘open’ position continuously? And does the valve simulator connect to the actuators / linkage / whatever flips when you press the performance exhaust button? I haven’t had a chance to examine this myself, nor found any drawings, so I’m flying blind a little bit.

But, honestly, after watching some vids w cat deletion and some of these aftermarket exhaust systems I’m kinda keen on the idea of the new louder growl!

EDIT: found a very useful thread on this subject and I think my options are clear now: https://mbworld.org/forums/c63-c63s-...s-coupe-5.html

thanks mbworld bros!

I don't wanna beat a dead horse but can we just get something clear first............. is the car still quiet with the exhaust button on OFF position with this done? Or is there some sorta increase in sound when the H-pipe is welded closed permanently and the exhaust is switched OFF?

I don't get it. There has to be a reason for the H-pip valve's existence other than just annoying us with rattles?




Regards,
George Lisciandro

Some stuff I found and posted before..:

"H-pipe sections were first installed to quiet this exhaust noise. When the two close firing cylinders are exhausting on one bank, there is nothing happening in the other bank, so connecting both pipes effectively enlarged the exhaust system, allowing these exhaust pulses to exit through both sides of the system. It was found that, with the addition of an H-pipe, exhaust noise could be reduced by as much as 2 decibels."

The exhaut button in the car has no impact on the H pipe valve. That is only for the valves in the muffler.

H pipe valve opens/closes under load. Initially when we just took out the H section with straight pipe we noticed that the car lost its growl which led us to believe that the H valve stays open in lets say C mode and then closes as you put load on it. Hence once the straight pipe was welded shut from the middle acting as if the H valve was closed, the car regained all its glory.

Summary: doesnt make the car louder. just gets rid of the annoying rattle and sounds as if in stock form the H valve is always closed which is what you want anyway.

Excellent bit of info thanks for posting this 👌

If you want the best sound, the pipe should be welded shut. As in delete that H pipe if you want a louder exhaust system. The valve opens to make the car quieter.

H-pipes equalize the exhaust gasses from each bank of the engine. Having the H-pipe valve open creates a more equalized and nice AMG sound because you're joining the two banks together. H-pipes (like X-pipes) can also be used for either torque down low or up top depending on what design it used (they each have their own scavenging advantages). Keep in mind, as mentioned, the H-pipe valve is not controlled by the exhaust button. It's controlled by the ECU and will open anywhere between 0-100% depending on engine load, RPM, etc. so it's dynamically changing how open or closed the valve is based on those conditions. This helps tremendously with the sound/tone.

I would recommend keeping the factory performance exhaust. No aftermarket catback beats the sound of the OEM tone, especially when paired with opened valves and a high flow cat or secondary cat delete.

Get a AWE valve simulator as mentioned, chop out the h-pipe with valve, and weld in a straight pipe to join the two pipes/banks.

Got it! I think this is what ill try.


now, just to unreasonably complicate the question...

1. If the H-member were removed completely, and holes closed on each pipe, would that be any different than welding the butterfly valve shut inside the H?


...I probably wouldn’t go this route even if there were a difference... because it would be immediately obvious to a tech that something has been screwed with... and it might affect the bracing and balance of the pipes. But immaterial questions like this is what forums are for right?

This also feels like sound advice (badum-chh) - Ill
sleep on the open H vs closed H Debate before the welder goes to work.

What if I get them to chop the pipes a little further up and behind, and bend a little X-pipe instead? Any theoretical outcomes?

Forum members have confirmed that just a straight H pipe with no valves makes the car sound considerably worse. Whereas closing it improves the sound. Also there is a 2nd H pipe towards the rear of the car which also equalizes both banks. So all in all, just get rid of it.

To answer your other question, yes welding the valve in closed position is the same as getting rid of the H pipe and welding the holes shut.

is that actually a second H? I haven’t been underneath to check - so I’m not doubting you - but there was a forum discussion about the secondary cross tube being nothing more than a brace

Nope, that's not an H-pipe it's just a brace. Looks like an H-pipe though.

Correct, there's only one H-pipe. Thankfully. Imagine having two of those nasties rattling away 🥴

A second H pipe huh?



There is no second H pipe.

WRONG!

Didn't know that was just a brace. Thanks for the correction.

:-)

What a nightmare that would be if there were 2 of those darn things...

Sorry for my comment. Was just taking the **** mate............ fixed my post 👍👍👍

And yes that would be quite a thing if there was two h-pipes rattling away 😓😓😓

You don't understand how H-Pipes function and what their purpose is in terms of sound and performance if you think that.

I've done you the hard work and started the video at the place you need to watch - maybe you'll understand better when Chris Harris explains it. (12 minutes, 10 seconds)

youtu.be/n4XUTu2lzTo?t=730

Not knocking the video and I've watched it dozens of times but it's not a good explanation of how the H-pipe works.

What exactly does old mate mean when he's pointing at the H-pipe and claiming "the flap controls the quality of the noise"?

Quality is a fairly vague description 🙄

Can you help and explain it for us please Alex?

And further, if he's saying the H-pipe controls the quality........... would the quality (whatever that means) be diminished if that H-pipe was removed or blocked off to stop the sh*tty rattles?

The main issue people have with the H pipe is the valve in the middle ( item 1)
if you remove the H pipe , then you get different issues and responses
if you weld it straight thru or block it, you get different responses

By responses I mean ( tone, notes, sound, some possible performance due to back pressure etc etc etc)

George, the reason why X-pipes and H-pipes exist is to merge the exhaust pulses from each bank of the engine to equalize the sound. An X-pipe will sound entirely different than an H-pipe. A true dual exhaust with no crossover pipe will sound completely different than if you merged them with either an X or H pipe. They allow you to tune the resonance and sound of the exhaust, and by having a completely adjustable H-pipe that can be 0-100% open, AMG can program at exactly what engine load, RPM, or condition to open or close the valve for the best sound resonance and allows for performance benefits like low end torque. But primarily, it's for sound. Make sense?

Good explanation thank you. A lot better than old mate Chris's quality spiel...........

So to keep this quality unharmed can we keep the H PIPE, remove the flap motor and weld the old flap in CLOSED POSITION? Obviously code out the CEL/install an AWE simulator?

I've had my H Pipe replaced on my c63s coupe twice under warranty now and the the rattle is still there. It's so annoying, been reading a lot about different options and from my understanding the easiest thing to do is have the valve welded shut, this won't affect performance and sound. I'm looking for a simple answer here so is that right?