Flapper valve in GM truck exhaust !?

[AZjeff]

Was under the '16 Silverado today looking for a small rattle and came across this thing in the exhaust pipe just after the muffler. Called an adaptive valve, it's a spring loaded weighted flapper who's job is to attenuate exhaust noise to eliminate the annoying low frequencies. Apparently they can also fail causing an annoying rattle and also in rust areas they can get stuck shut. Exhausts last forever here so I'd have to intentionally eliminate it. Sounds like an answer looking for a problem, thanks GM. At least it's not computer controlled voodoo magic.



Video from company that makes them:

 

[Chris142]

That would never worked when I was younger. All our cars idled like rumpityrumpity.

 

[4WD]

Originally Posted By: Chris142
That would never worked when I was younger. All our cars idled like rumpityrumpity.


Oddly enough the last time I heard that sound was in Australia … prince of a Bel Air (‘57) …

 

[04SE]

1- 2" long 1/4" bolt
2- 1" diameter 1/4" washers
1- 1/4" lock nut

Turn valve 90 degrees.
Stick bolt with washers on each end into gap of valve.
Thread lock not on.
Tighten.
Voila - it is now open.

Mine sounded like a helicopter in 4 cylinder mode and lost a noticeable amount of low end torque with it bolted open.

People can say that I am crazy but I had mine bolted open for about 5 minutes and couldn't get the bolt out fast enough.

 

[slacktide_bitog]

Isn't that something like what the Dynomax VT uses?

And on the OEM side, the Silverado is hardly the only one that comes with an exhaust flapper. For example,I think some Mustangs come with one, too.

 

[AZjeff]

Originally Posted By: 04SE


Mine sounded like a helicopter in 4 cylinder mode and lost a noticeable amount of low end torque with it bolted open.

People can say that I am crazy but I had mine bolted open for about 5 minutes and couldn't get the bolt out fast enough.


Interesting that you noticed a loss of performance, the only stated purpose per the manufacturer is changing the exhaust frequencies, not enhancing torque. I'm going to have to jam it open and see what happens.

RE exhaust valves in Mustangs, maybe so, I never knew about these things until today.

Edit to add: Mustang exhaust valves are user select-able and work through the ECU to purposely increase performance and sound level. Totally different.

 

[dishdude]

My car has a similar setup, but it's controlled by the ECU. Opens on startup and when you get on the throttle but quiets down when you're cruising. Apparently the drive mode you select also determines how much exhaust sound you hear.

 

[Olas]

Cut it off and weld the hole shut

 

[billt460]

Can you soak it with some high temperature lube? Or else paint it with high temp anti seize? It really looks dry and rusty.

https://www.walmart.com/ip/LOCTITE-51147...13=&veh=sem

 

[AZjeff]

Not rusty that's road grime from the rain. I could see it on a car or SUV but on a truck?

 

[JTK]

Is this thing only on the V6 powered Silverados?

 

[AZjeff]

It looks like it's in any GM truck from about '14 up with cylinder deactivation.

 

[glock19]

If you check out any of the Silverado/Sierra forums, a lot of people are complaining about these flapper valves rattling (sounds like a can of marbles). The other common issue is a tick under load. It sounds like an exhaust leak, but even guys with aftermarket exhausts experience the problem. As far as I know, no one has solved that issue yet.

 

[circuitsmith]

Originally Posted By: slacktide_bitog
Isn't that something like what the Dynomax VT uses?

And on the OEM side, the Silverado is hardly the only one that comes with an exhaust flapper. For example,I think some Mustangs come with one, too.


I've seen BMWs with them since the 90s.

 

[circuitsmith]

Originally Posted By: glock19
The other common issue is a tick under load. It sounds like an exhaust leak, but even guys with aftermarket exhausts experience the problem. As far as I know, no one has solved that issue yet.


Does that engine have variable valve timing?
Exhaust valve opening time could have something to do with it.

 

[glock19]

Originally Posted By: circuitsmith
Originally Posted By: glock19
The other common issue is a tick under load. It sounds like an exhaust leak, but even guys with aftermarket exhausts experience the problem. As far as I know, no one has solved that issue yet.


Does that engine have variable valve timing?
Exhaust valve opening time could have something to do with it.


Yep, continuously variable valve timing.