[KingLT1]

Originally Posted by chozn4service

I have the American Thunder Flowmaster exhaust with the Scavenger X pipe and it sounds down good to me and is everything I ever wanted in an exhaust.

That is how mine sounds with the valves open. My complaint is when the valves are closed, they don't seal and make a hissing sound.

https://youtu.be/rMmg8eJdqC4

[70chevelleSS]

Originally Posted by KingLT1

That is how mine sounds with the valves open. My complaint is when the valves are closed, they don't seal and make a hissing sound.

https://youtu.be/rMmg8eJdqC4

Yea mine definitely doesn’t sound like that when closed. I wonder if your valves have gotten dirty somehow or collected buildup which may keep them from fully closing?

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[chozn4service]

Mine either.... as stated above, maybe some build up on them? Wonder if maybe shooting them with some carb cleaner and using an old tooth brush and then spraying again might resolve the issue. I’ve have mine virtually since getting the car new in 2016 and still sounds great and seemed to have gotten deeper along the way.
I’d like to do headers but seems as tho they won’t mate up to the Scavenger X so I’ve been told and ARH and KOOKS wants to sell be a catback, tho MOTOFIRE on IG says it will work. Just need confirmation before I make that move but I can only imagine what it would sound like.....


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[KingLT1]

Originally Posted by 70chevelleSS

Yea mine definitely doesn’t sound like that when closed. I wonder if your valves have gotten dirty somehow or collected buildup which may keep them from fully closing?

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The exhaust is brand new. I even tried oiling the valve shafts. When I shine a light in the pipe, the valve doesn't look concentric with the pipe. I must of received a axle back built on a Monday.

[KingLT1]

Still no word yet from Flowmaster. CS rep said he is still waiting to hear back from the product group.

[70chevelleSS]

Originally Posted by KingLT1

Still no word yet from Flowmaster. CS rep said he is still waiting to hear back from the product group.

While I have not noticed the noise that yours makes, I have noticed that my valves don’t shut 100%. Essentially I can put mine in stealth mode, and still get some flow on the outer pipes. It gets quieter if I cover the outer pipes with my hands. I assumed this was just the nature of these valved exhausts, but it could be related to the problem you are experiencing.


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[KingLT1]

Originally Posted by 70chevelleSS

While I have not noticed the noise that yours makes, I have noticed that my valves don’t shut 100%. Essentially I can put mine in stealth mode, and still get some flow on the outer pipes. It gets quieter if I cover the outer pipes with my hands. I assumed this was just the nature of these valved exhausts, but it could be related to the problem you are experiencing.


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It is but mine don't close as far as they do on initial startup after I have driven it and that is when they start making the hissing noise. If I use a screw driver I can push them closed 1/16" or so and the hiss goes away, then the sound is similar to what you describe.

I'm going to try some stuff in the exhaust valve tuning and see if I can fix it. It almost seems like the valves need to be turned a tad further then the controller is turning them in order to seal. I am going to try using a value higher then 100 in the closed cells and see what happens.

[6spdhyperblue]

Anyway to cheat on the valves and get them to turn a bit in that direction and retorque the bolts? Are they the oem actuators that boot in there?

[KingLT1]

Originally Posted by 6spdhyperblue

Anyway to cheat on the valves and get them to turn a bit in that direction and retorque the bolts? Are they the oem actuators that boot in there?

Yeah OEM actuators. I'm going to try some things and see what happens.

[MAGAUSA]

Mine has that hissing sound with the valves closed too. Much better than the stock "rattle" but still annoying.

[KingLT1]

Originally Posted by MAGAUSA

Mine has that hissing sound with the valves closed too. Much better than the stock "rattle" but still annoying.

Thanks for reporting. Yes I agree, I will just leave the valves open at idle and cruising, then have them close in 8th gear so it eliminates the drone.

[6spdhyperblue]

Does it hiss at the low cfm at cruise or just when pushing a bunch of air through them?

[KingLT1]

Originally Posted by 6spdhyperblue

Does it hiss at the low cfm at cruise or just when pushing a bunch of air through them?

its only noticeable at idle with the exhaust valves closed(touring/stealth) when you stand behind the car, or backing into the garage with the windows down. Most probably leave the car in sport and never notice it, but since I have cat deletes, it makes the exhaust significantly louder. I had my valves programmed to stay closed in all modes until 3-4k rpm then open.

[KingLT1]

Just an update...Holley performance group is sending me a brand new axle back exhaust. It's been a slow process but nonetheless they are taking care of me.