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Hi all, I've spent the past month or so developing my take on the exhaust valve/flap bypass to keep it open cheaply! After some poking and prodding, the car as stock will cycle the flappers when the engine fires up and when it shuts down. If you simply unplug or mechanically disconnect the flapper motor from the flaps, you will get a CEL (at least for my '23 G550).
I didn't want to pay close to $1,000 (before installation) to semi-permanently add remote control to my exhaust valves when I know I just wanted to keep them open. I also didn't want to reprogram the car because who knows what that might do to my warranty.
I knew I could design something simple that installs very quickly. It only takes about 10min per side and can easily be put back to stock without any trace of the mod. It is simple enough that even non-DIY'ers can confidently install it. The flapper motor sits higher now but even when pushing the exhaust up as hard as I could, it still did not cause any interference or contact.
So I have been enjoying my exhaust notes open and flowing for the past month but now looking for testers who want to try it for free. I am targeting the final kit cost to be ~$100 (CNC machined and anodized aluminum) depending on the level of interest.
And now for some pictures of the prototypes/beta test kit. They all worked well but the early designs used a rigid connection pin and I worried about putting additional stress on the flapper motor. The latest design reuses the original connection spring so it functions nearly the same as the factory setup.
The end goal is to cheaply fool the flapper motor without any adverse effects - using parts that are easily and quickly installed/removed without leaving a trace.
Current iteration fully assembled
Current iteration body mounted
Exhaust flap safety wired open
Summary of iterations
Third (current) iteration with a sintered body and reused connection spring from OEM
Second iteration with a CNC machined and anodized body and sintered connection pin
First iteration with a sintered body and dowel connection pin
Thanks guys. What does the open exhaust flap button look like? It's an AMG only thing right?
The current prototype is 3d printed by sintering aluminum powder. Some of the previous parts were made from stainless steel powder.
Thanks guys. What does the open exhaust flap button look like? It's an AMG only thing right?
The current prototype is 3d printed by sintering aluminum powder. Some of the previous parts were made from stainless steel powder.
I had a 2019 G550 with sport exhaust, as you mentioned there is no exhaust button. I could only open the exhaust in Sport mode, and from what I hear, the exhaust doesn't fully open all the time and is variable.
So your mod should make the exhaust overall much louder at all RPM's.
As you mentioned, these are the current other options:
Hi all, I've spent the past month or so developing my take on the exhaust valve/flap bypass to keep it open cheaply! After some poking and prodding, the car as stock will cycle the flappers when the engine fires up and when it shuts down. If you simply unplug or mechanically disconnect the flapper motor from the flaps, you will get a CEL (at least for my '23 G550).
I didn't want to pay close to $1,000 (before installation) to semi-permanently add remote control to my exhaust valves when I know I just wanted to keep them open. I also didn't want to reprogram the car because who knows what that might do to my warranty.
I knew I could design something simple that installs very quickly. It only takes about 10min per side and can easily be put back to stock without any trace of the mod. It is simple enough that even non-DIY'ers can confidently install it. The flapper motor sits higher now but even when pushing the exhaust up as hard as I could, it still did not cause any interference or contact.
So I have been enjoying my exhaust notes open and flowing for the past month but now looking for testers who want to try it for free. I am targeting the final kit cost to be ~$100 (CNC machined and anodized aluminum) depending on the level of interest.
And now for some pictures of the prototypes/beta test kit. They all worked well but the early designs used a rigid connection pin and I worried about putting additional stress on the flapper motor. The latest design reuses the original connection spring so it functions nearly the same as the factory setup.
The end goal is to cheaply fool the flapper motor without any adverse effects - using parts that are easily and quickly installed/removed without leaving a trace.
Have you tried these on a G63 yet? I had the Renntech module on a 2021 G550 that worked well but was a pain to install. I haven't done anything to my G63 but would certainly help you test it out. I actually work in the automotive aftermarket corridor and have my entire adult life. I applaud the effort here. Looks well done.
Hi very interested in this I cannot PM you since I am new can you please PM me?
Originally Posted by myfirstg
Hi all, I've spent the past month or so developing my take on the exhaust valve/flap bypass to keep it open cheaply! After some poking and prodding, the car as stock will cycle the flappers when the engine fires up and when it shuts down. If you simply unplug or mechanically disconnect the flapper motor from the flaps, you will get a CEL (at least for my '23 G550).
I didn't want to pay close to $1,000 (before installation) to semi-permanently add remote control to my exhaust valves when I know I just wanted to keep them open. I also didn't want to reprogram the car because who knows what that might do to my warranty.
I knew I could design something simple that installs very quickly. It only takes about 10min per side and can easily be put back to stock without any trace of the mod. It is simple enough that even non-DIY'ers can confidently install it. The flapper motor sits higher now but even when pushing the exhaust up as hard as I could, it still did not cause any interference or contact.
So I have been enjoying my exhaust notes open and flowing for the past month but now looking for testers who want to try it for free. I am targeting the final kit cost to be ~$100 (CNC machined and anodized aluminum) depending on the level of interest.
And now for some pictures of the prototypes/beta test kit. They all worked well but the early designs used a rigid connection pin and I worried about putting additional stress on the flapper motor. The latest design reuses the original connection spring so it functions nearly the same as the factory setup.
The end goal is to cheaply fool the flapper motor without any adverse effects - using parts that are easily and quickly installed/removed without leaving a trace.
Current iteration fully assembled
Current iteration body mounted
Exhaust flap safety wired open
Summary of iterations
Third (current) iteration with a sintered body and reused connection spring from OEM
Second iteration with a CNC machined and anodized body and sintered connection pin
First iteration with a sintered body and dowel connection pin
I found an area of necessary improvement with this kit but I bought a new exhaust some time ago so the design changes were never made.
Maybe I'll come back to it...
That is the maker and supplier for the Renntech ones, problem is Renntech licensed it to be sold in usa for double the cost and asr doesn't ship to usa.
Hey, would you be able to sell me a copy of the design or the parts for the flaps? I am in a pinch to eliminate these exhaust flaps. I can carbon 3D print the parts.
Thanks you!
Last edited by MBCreator; Feb 26, 2026 at 12:52 PM.
Or if you can sell me a set of what you have already created and I will make them work. I understand you mentioned that you want to change the design a bit, but I am totally fine with how they are and I will figure out the rest.
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