Zeker

Out of nowhere a rattle started from my exhaust today. Its only audible when giving throttle. Butterfly valve failure? The car is tuned and has the secondary resonators cut out - should i have them welded back in (something i wanted to do anyways) and re-flash factory before taking it in?

Simbad

Why did you want them welded back in. Curious as someone that is considering getting this done.

Zeker

I have the performance exhaust on my car and after having them removed it didnt sound as deep anymore

Zeker

To follow up here. Cats went back in and im not happy about it - preferred them out. The good news is the repair is being covered by MB under warranty (so good thing i put them back).

Exhaust had something rattling inside of it so there is a new system on order from germany. Should have it back in a few days

Simbad

Mine seems to have the tiniest of rattles that I only notice when. Off the gas and slowing down almost like a tiny pebble got into the exhaust. It’s not noticeable to most people but for the **** type like me.
Anyone else sense that. Slowing down no throttle.
It’s not the normal decelerate noise.

doctorG

I have begun to hear this as well. It almost sounds like there is a small piece of metal between the brakes and the rotors scraping, but it is definitely the sport exhaust because turning off the sport exhaust while cruising off throttle makes the noise disappear.

Going to take it in soon to see what dealer thinks.

Anyone else have any thoughts?? Thanks!

thecutter64

It’s probably the flap valve in the sport exhaust.

doctorG

Is it defective or normal? It doesn't sound normal, but I could be wrong.

pchiu408

@Simbad @doctorG did either one of you either have the exhaust sound resolved? I have a 2016 with the same issue. It's like a loose flap/metal grinding sound. Only happens with the flaps open and as soon as i close them, it goes away. Comes back when I open the flaps.

Orcbolg

There's a discussion going on about this topic a few thread down:

https://mbworld.org/forums/coupe-roa...ml#post8252812

doctorG

No, the rattle is still there and I was basically told that it only happens at “low load” because the exhaust valves need more load (higher RPMs) to not make that noise. I have no idea what the right answer is, but they basically told me it is normal...frustrating to say the least. I’m starting to wonder if I should pursue the issue again based on what I just read in the linked thread above about the 2020 GTR.

If someone identifies something that I can clearly go to the dealer with I’d appreciate it. Thanks!

SpokenHands

Had the exhaust rattle - very annoying and apparently its the butterfly exhaust valve when in open position
Naturally you hear it at lower speeds when the car is in S / S+ / race mode

Problem fixed by my AMG specialised tech who applied a specific grease that is ordered in.
No rattle now but will likely need to be greased again in a couple of years.

C63S definitely has a similar rattle according to him

Beeast

They did this to mine, it did not fix the issue. I hope you have a different outcome.

Beeast

My tech told me that there is a one page guidance on the rattle (GTR) and that it is "normal" for a supercar. He followed that with an if they wrote a document that length as a bulletin then they are getting a lot of complaints about it.... I was told that they narrowed it to a mapping issue which should be released in a few months. Other members have been given that same guidance, but over a year ago and still have no resolution. It was recommended to me to get the EVM from Renntech, but I have not had anyone verify that fixes the issue if the exhaust is already rattling.

From what I can tell, loosely; Stock GTR - Comfort mode= closed OR Sport/Sport+/Race= ~75% open to 100% open depending on mode and throttle... My assumption is the new mapping will eliminate that 75%-100% and make it fully open. If you get the Renntech EVM, it will give you the 0% or 100% unless you turn off the EVM and just let it do stock noise. Eliminating that in-between area puts less wear on the butterfly flap allowing it to keep the sound consistent and superb. Otherwise you risk flutter and/or sticking which can and has impacted turbo boost.

I am no expert, just a new owner troubleshooting via the internet and my tech.

GTaddict

The EVM has solved the existing rattle on my 2020 AMG GT R when it is in “OPEN” mode. I did not change any exhaust parts, nor has my dealer tried lubricating the valve (this will not work for this particular problem). The EVM in “OPEN” mode will keep the valves open all the time and will prevent the rattle from occurring. The valve positioning for the 2020 GT R’s has been set incorrectly by the factory at certain (lower) RPM ranges which unfortunately causes this rattle. This simple modification is a bandaid, essentially acts like deleting the valves. It sounds louder now at lower RPMS, arguably sounds like how it should have sounded from factory.