Thanks for the pic man I needed this today. Ended up getting mine welded and locked & plugged in the AWE simulator. No more rattle.

Totally forgot how rowdy this car sounded especially the upshift gear change burp fuk blew me away.

Random gurgles on the overrun and when coming to a stop are back now too. Happy days

https://cimg9.ibsrv.net/gimg/www.mbw...8bb78d9e3f.jpg

Man, this was waaaaaay too much well than you would have needed I think. Just a spot weld would have been good enough.

Yeah I know. Showed the exhaust guy your picture with the blue dot and he had a hard time reading the markup notes. He was pinching and zooming in all over the place. Then I ended up with the "blob" 🧐

Thank God for your pic though.

What would the advantages and differences be between replacing this valve, and getting the valve flap welded closed and using AWE simulator?

And per the Holley website, it is not smog-legal. Is the AWE simulator and weld fix smog-legal?

EPA pretty much states anything that touches or swaps out parts on the omissions is OFF ROAD or RACE only. Its a Cover Your A$$ statement.

Gotcha. Makes sense. So then what would be the advantage of the Holley product over the spot weld and AWE simulator? Is there something better about the Holley product that improves the sound and/or quality of the H-pipe valve over stock?

The Holley product is more robust and high quality compared to our stock valve flaps. AWE use the Holley valve for their exhausts and it's very strong and built better than the Mercedes valve flap.

The Holley valve flap also use existing Kuster valve motors (ours). So it's just a weld in and you're set.

From my experience during this saga, the way our H-pipe valve opens and closes depending on RPM works really well for sound. Especially if you have secondary cats removed, it's always nice to have a functioning H-pipe.

As you know, keeping the H-pipe open all the time will rob you of the deep sound, but having it shut the whole time also gives you a bit of in-cabin vibration on light throttle under 2000-2500rpm when the exhaust is "ON". This is what I experience with my coupe and the windows are up and having the secondary cats deleted.

It sounds menacing with the H-pipe closed permanently when you're driving hard, but sometimes when you just want that nice, throaty sound without the vibration drama, you can see why the H-pipe exists as it will Open to reduce drone as you take off, but Close as you're accelerating. Hence why the rattle happens above 2500rpm because this is when the H-pipe valve begins to close and the rattle is from the spindle (the round part that the spring sits on top of) not being completely shut, due to weak spring tension.

And that's why when you stretch the spring, it will be able to hold down the spindle harder whilst the H-pipe starts to close and exhaust gasses are hitting the closed flap.

Having weak spring tension allows just a small amount of play in the round spindle (where the spring sits on). This spindle begins to "tap" back and forth as exhaust gas passes the flap in it's closed position due to the weak spring tension.

You can emulate the rattle by taking off your valve motor and twisting the spindle rapidly. The "tap tap" sound from this spindle is the actual rattle you hear. Not the flap that's inside the H-pipe.

Thank you for the clarification. So does this mean that I should still plan to adjust the valve motor spring tension even if I get the Holley H-valve?, in order to eliminate rattle? Or does the presence of the better (Holley) valve eliminate the need to adjust spring tension?

I'll be testing a Holley H-pipe valve when they have them in stock within the next couple of months so i'll let you know, but there has been zero complaints about rattling or anything of that nature for the past few years

Earlier AWE exhausts had some H-pipe issues in the past but this has been fixed for at least 3 years now.

I've also been researching other forums and car makes such as Mopar, Audi, Ford and Volvo who also have members who've used or added these Holley valves to their aftermarket exhaust setups and they are of very build good quality. I guess that's why they are a bit pricey, too ($430 USD).

In the meantime, if you want to keep your H-pipe functioning without the rattle, the guaranteed way to fix the problem on our H-pipe is by increasing spring tension.

I've even used a stretched out/upgraded spring (below) and it worked but it was just way too tight of a fit and I didn't like how it pushed too hard against the valve motor's plastic spring seat.

Stretching our spring to increase tension a bit is still the best way if you want to keep the factory H-pipe working and rattle free.
https://cimg0.ibsrv.net/gimg/www.mbw...3cb1f49362.jpg

And the link for Holley, provided earlier in this message thread, which directly goes to the

HOOKER BLACKHEART ATTITUDE ADJUSTER EVC

Replacement Valve...
It will also fit for 2021 C63S AMG with Performance Exhaust?

Also, on this thread, I have separately read multiple posts that say the opposite in regards to when the exhaust noise is louder. Some state that exhaust volume increases when the H pipe valve is either fully open, or absent. And have read where people weld the valve shut and that is what makes it louder. Can anybody provide clarity with this?

Just to confirm one thing here...

Is the aim of stretching the spring:
A) To apply more anti-clockwise force to the spindle to keep it closed, or
B) To apply more axial load (pushing towards the spindle) to stop some other chattering?

I see a mix of diagrams and photos and just want to clarify before I go ahead and mess with the spring this week.

Cheers

Sorry to bring up an old topic, but was looking at welding my H valve shut to enhance the sound (thanks @untamedd for experimenting) and then got into thinking in order to prevent limp mode, or modifying the valve or using simulators to trick the car. Would it have the same effect welding a disk on either side of the h valve? That way the h valve is still free to open/close as per programmed logic but no exhaust flow going through? Thoughts?

initial steps taken were not to enhance the sound but to keep original sound without the rattles.. whether or not your experiment enhances the sound is something to be seen. maybe you can share your findings here if you do decide on trying it out.

2021 c63s
 

Hey guys I read through all the comments and what people did to remove that tattle coming from the middle actuator flap. I just bought a 2021 c63s and imideattly I had the rattle issue. The dealer even replaced all 3 actuators including the ones on both mufflers but the rattle was still there. I took it the car to a mechanic exhast shop I trust and have been going to for over a decade. They ended up removing the spring in the middle of the ahaust where that spring is and welding the flap closed. The rattle is completely gone but now the car is not as loud with the valve shut closed. I have two questions. If someone could shed some light.

1.Is removing the spring and welding the middle valve close create any issue? Or can? (Might be a stupid question I apologize)

2.How do I make the car louder? Do an x or h pipe and bypass the actuator by puting in a bypass plug? I am trying to avoid doing cattless downpipes.

Are you sure they welded it shut? Show us a photo?

When it's welded shut the car is DEFINITELY louder and more "boomy". I hated both as the boomy noise would sort of drone at times so I completely replaced the H-pipe section with a second hand one and reinstalled the valve and used the uprated spring. Every now and then I will lubricate with a bit of copper grease and I haven't had a rattle in 12 months nearly. Thank fuuck

how we doing what if someone was to cut the h pipe out and not fit the awe simulator what wood that do?

Hey guys/gals,

I’ve been having the same issue with my 2017 C63s coupe with AWE track exhaust - yes even the h-pipe from AWE has issues….

I had my h-pipe replaced by AWE under their warranty back in April 2019 due to the valve making noise at idle…. Thought I would be done with this issue…

Fast forward to Spring 2023 - now the H-pipe is making a rattling noise = its coming from the h-pipe… Had it checked out and the valve is rattling - so bad at idle - makes me not want to drive the car and I love driving my car…. Reached out to AWE on Friday and waiting back for their response… I know it’s out of their warranty now but this is ridiculous…. Same issue 4 years later and now I see its not only me…

So it’s not just stock AMG performance exhaust - h-pipe having issues, but even aftermarket exhausts like AWE that are having H-pipe valve issues….

I might just do what everyone else is and have my h-pipe valve welded closed…. Going to see what AWE can do…..

I would post a video with the car idling and another video under my car when we were assessing the h-pipe valve but I’m not sure how to post videos ?????

I’ll keep you guys posted….

I’ve been reading through these pages and I’m having a similar problem, but mine seems to be more of an exhaust leak (ticking at 1500-3000rpm under load. The odd thing is, it only happens when the exhaust button is on (H-pipe flap closed). There is no noise when the exhaust button is off (H-pipe open). Does anyone have any suggestions? Perhaps I have an exhaust leak at the valve?

Thanks in advance

If you can, jack the car up and get under there with a spray bottle (mix a few drops of detergent with water) and turn the car on. Start spraying around the exhaust pipes and watch for bubbles. If you see some bubbles then there's your leak. You can mend leaks easily with JB Weld for exhaust. You can use the paste or the putty just roll it up in your hand and press it into the leaking areas and let it dry out.

Or you can get an exhaust place to weld the leaks for you. Check the H-Pipe section in particular

https://cimg6.ibsrv.net/gimg/www.mbw...acca6e2baa.jpg

I seem to be having this strange rattle now as well. It happens under mild load from 2.5 RPM to 3.5/4 RPM. 2019 C63s with secondary cat delete. What seems to be the final fix for this? Thanks for the help.

Easiest thing to do is just lubricate it with copper grease from the tub every 6 months. I use a small syringe and pump it through the holes it 100% works I've been rattle free for over 12 months now

Got it thank you I will give that a try.

I guarantee you it will work. The copper grease becomes a cushion and stops the flap from "clanging" on the cradle. That's what causes the rattle in the first place.

Mercedes lubricate it but their lube always turns hard after a few 100 miles and the rattle comes back. The copper grease won't go hard.

Please let us know how it goes. You only need to use 3x 5ml syringes worth and that rattle will be solved.

I use this syringe and poke it through the cradle holes to pump the grease in
https://cimg7.ibsrv.net/gimg/www.mbw...b16c532ef4.jpg