Renntech Exhaust Valve Controller
Thread Starter
Junior Member
Joined: Jul 2013
Posts: 45
Likes: 3
From: Ohio
2020 S560 Coupe & 2018 GLS63 AMG
Renntech Exhaust Valve Controller
Anyone have Renntech's Exhaust Valve controller installed? Curious how much difference it makes in the exhaust sound at lower speeds. Trying to justify $800 or whatever it is for basically a remote that tells the flaps to open/close lol.
Junior Member
Joined: Jan 2005
Posts: 60
Likes: 6
From: Palm City, Florida
2015 MB S550 Coupe, 2018 Carrera T, Ford F150
For those who are interested in this modification, I offer the following.
I became curious as to the operation of the exhaust valves and decided to look into it. I have a 2015 S550 coupe since new and previously used adjustable links to lower the suspension about 1.25 inches. I also replaced the brake pads with low-dust ceramic pads. Both changes were worthwhile and I have kept this car longer than any other in the past 30 years. I am very pleased with it.
So here's what I can provide regarding the exhaust valves. They are indeed vacuum operated and the vacuum relay, also known as a changeover valve in Porsche speak, is located in the trunk, passenger side, all the way to the rear. The only item more rearward is the auxiliary battery which surprised me because I thought it was further forward. Anyway, to reach the vacuum relay you remove the trim piece on the rear wall, below and surrounding the trunk latch. Then loosen and move the passenger side interior panel by removing 2 push pins, and the tie down point on the floor. All are easily found. Then swing the panel away toward the center of the car, follow the vacuum line along the rear wall of the trunk and it will end at the vacuum relay. The relay is below the fuse panel and held by a clip. Simply pull the vacuum relay up and will slide off the clip. Then you can disconnect both vacuum lines from the valve and join them together with a connector which is available at any auto parts store for less than a dollar. Doing this will cause vacuum to be always supplied to the two vacuum motors that control the flap on each side. It doesn't make a big difference in sound, but it is obvious if you listen for it. There's a little bit of a deeper and louder tone. It's most like the sound you get in sport mode. When the engine is turned off the valves stay open until the vacuum is replaced with air in the system. It takes about 24 hours for this to happen. Then when the engine is started the flaps open within 2-3 seconds as the air is drawn out and the vacuum is again present. It cost nothing but the price of the connector and about 30 minutes of your time to try this. I think you'll like it.
I became curious as to the operation of the exhaust valves and decided to look into it. I have a 2015 S550 coupe since new and previously used adjustable links to lower the suspension about 1.25 inches. I also replaced the brake pads with low-dust ceramic pads. Both changes were worthwhile and I have kept this car longer than any other in the past 30 years. I am very pleased with it.
So here's what I can provide regarding the exhaust valves. They are indeed vacuum operated and the vacuum relay, also known as a changeover valve in Porsche speak, is located in the trunk, passenger side, all the way to the rear. The only item more rearward is the auxiliary battery which surprised me because I thought it was further forward. Anyway, to reach the vacuum relay you remove the trim piece on the rear wall, below and surrounding the trunk latch. Then loosen and move the passenger side interior panel by removing 2 push pins, and the tie down point on the floor. All are easily found. Then swing the panel away toward the center of the car, follow the vacuum line along the rear wall of the trunk and it will end at the vacuum relay. The relay is below the fuse panel and held by a clip. Simply pull the vacuum relay up and will slide off the clip. Then you can disconnect both vacuum lines from the valve and join them together with a connector which is available at any auto parts store for less than a dollar. Doing this will cause vacuum to be always supplied to the two vacuum motors that control the flap on each side. It doesn't make a big difference in sound, but it is obvious if you listen for it. There's a little bit of a deeper and louder tone. It's most like the sound you get in sport mode. When the engine is turned off the valves stay open until the vacuum is replaced with air in the system. It takes about 24 hours for this to happen. Then when the engine is started the flaps open within 2-3 seconds as the air is drawn out and the vacuum is again present. It cost nothing but the price of the connector and about 30 minutes of your time to try this. I think you'll like it.
