Does Anyone Know What This Valve is Called or What It Does?

[WillieFlo]

For the last few months, my wife's Denali has sounded like crap for about 10-15 seconds on cold start ups in the mornings. Well, I finally got it on jack stands, slipped underneath it, and was able to pinpoint the culprit of all the clattering and clanking going on. There's a valve between the cat and the muffler with a rotating spring controlled knob on it staying shut......The spring is kind of weak, allowing the valve to stick closed until it warms up. It causes a bunch of clattering and sounds like a bunch of plastic pellets bouncing around inside the exhaust or muffler. The valve also makes a metal clanking sound until it finally opens......Noise is gone now that I rotated it back and forth a few times, and hit it with some dry lube/graphite.

Does anyone know what this valve is for and what it's called?

 

[tirekicker]

hey..there really is a such thing as a muffler bearing ! just kidding ...everyone calls it a "flapper" and its to help with drone when switching to v4 and back

 

[Denali Brad]

Pretty sure that's the Fetzer valve...

 

[OR VietVet]

I think if you lube that "muffler bearing" the noise will go away. I thought, did not know at all, that it looks like it is for partial exhaust flow blockage to help heat up the cats and then when hot enough it opens fully. I do think I heard the word "flapper" valve on here before but unsure and know I have not heard of a "Fetzer Valve" anywhere.

 

[iamdub]

People usually lock it in the open position. IIRC, the most common method is called the "bolt mod". I've seen hose clamps and stainless tie wire used as well.

 

[WillieFlo]

Thanks all!

 

[gooffeyguy]

For the last few months, my wife's Denali has sounded like crap for about 10-15 seconds on cold start ups in the mornings. Well, I finally got it on jack stands, slipped underneath it, and was able to pinpoint the culprit of all the clattering and clanking going on. There's a valve between the cat and the muffler with a rotating spring controlled knob on it staying shut......The spring is kind of weak, allowing the valve to stick closed until it warms up. It causes a bunch of clattering and sounds like a bunch of plastic pellets bouncing around inside the exhaust or muffler. The valve also makes a metal clanking sound until it finally opens......Noise is gone now that I rotated it back and forth a few times, and hit it with some dry lube/graphite.

Does anyone know what this valve is for and what it's called?

View attachment 343409

Doesn't it have "DRONE VALVE" and a part# stamped on it?

 

[WillieFlo]

The Left side of it was unreadable due to the corrosion, staining, etc..........all I could see was "VALVE".

 

[STORMIN08]

i hose clamped that dude wide open long ago...helps keep it from rattling as it gets weak

 

[gooffeyguy]

Lets not forget that Cardi B song (WAP) that everyone plays and it even won awards at the American Music Awards LOL

Actually, I'd like to forget it, but still, funny how that crap doesn't get censored as much as much less ****** words

 

[Jeff_]

I've been told I shouldn't do this mod to keep it permanently open if I don't have AFM disabled otherwise it'll sound like ****. Is that truly the group consensus?

 

[STORMIN08]

it does sound odd in V4 mode.

 

[iamdub]

I've been told I shouldn't do this mod to keep it permanently open if I don't have AFM disabled otherwise it'll sound like ****. Is that truly the group consensus?

Which will sound shittier- the constant metallic rattling or an odd engine note only when in V4 mode?

 

[WillieFlo]

i hose clamped that dude wide open long ago...helps keep it from rattling as it gets weak

So, when the vehicle is off, I assume that spring pulls it into the "closed" position? When the vehicle was off, I could turn it about 5-10 degrees in one direction, and the other direction it rotated about 90 degrees. So, I held it turned in the 90 degree position while I wired it like that. Hopefully, that holds it open, but just want to confirm that was the correct assumption. No more rattling on startup.

I have the Borla exhaust on mine and am interested to see what it sounds like in V4 mode on the Highway.

 

[iamdub]

So, when the vehicle is off, I assume that spring pulls it into the "closed" position? When the vehicle was off, I could turn it about 5-10 degrees in one direction, and the other direction it rotated about 90 degrees. So, I held it turned in the 90 degree position while I wired it like that. Hopefully, that holds it open, but just want to confirm that was the correct assumption. No more rattling on startup.

I have the Borla exhaust on mine and am interested to see what it sounds like in V4 mode on the Highway.

Yes. The spring tension is balanced so that the air volume when running on all eight cylinders keeps the valve open. When running on fewer cylinders, the engine is pumping less air. A full-open exhaust sized for a V-8 but with half that volume going through it is like the typical oversized free-flowing exhaust on a compact car ("import") with a fart cannon. With the engine off/no air flowing through the exhaust, the valve would be at its minimal position. I doubt this would be "fully closed" as that would be pointless, but it'd have to be against a stop of some sort.

 

[BigBlueLB756]

It's So easy.

 

[17 Yukon Denali]

It's a Dinglehopper. EVERYONE knows that,

 

[OR VietVet]

It's a Dinglehopper. EVERYONE knows that,

Well, we do now.