Screens or Flappers

[Gangly]

For those who have removed flappers, locked flappers open, or covered resonance screens, I have two questions:

 

1.  Which of the three modifications affected drone the most?  

2.  Which of the three modifications affected tone the most?

[19Sierra]

I wired the flapper open on my 19 5.3l single exhaust and there is no drone. Actually I cant even tell a difference in sound at all. Reason I wired it open was because it was causing the exhaust to whistle, now it doesnt whistle. I havent done anything with the screens.

Edited June 10, 2020 by 19Sierra

[SquireSCA]

Covering the screens will make it drone.  Leave those intact unless you enjoy droning...

[Rpitz56]

Another vote for screens being the biggest contributor to drone. Did a muffler delete on my '19 5.3L, dual exit, I have the screen towards the front of the truck, on the passenger side, open. And I'll have to verify, but I believe the rear or middle screen open on the driver side and it removed the helicopter drone, completely. This screen combination allowed the idle to remain louder, and deeper, than leaving them all open. 

Edited June 19, 2020 by Rpitz56

[smald081]

Ok fellas here it is from someone who has actually done it. I Installed the Borla Atak muffler 2.5 off center inlet to center outlet. Off the top of my head part number was 400826... I tested the sound absolutely no drone with flapper valve removed. Then to further testing I covered the mesh resonators and love the sound now. Perfect no drone whatsoever. 2020 LT trail boss 5.3 muffler shop charged $100.00 got the muffler for 230 on sale for fathers day 

Edited June 24, 2020 by smald081

[Ratchetarms]

Stock exaust. Clamped flapper open.  Slight in crease in sound at startup.  No drone. After a while I covered all 6 screens.  Notable increase in sound at low rpms. Perfect for me. I haven't noticed any drone, even pulling a horse trailer. I know exhaust sound is completely subjective. I don't want a loud exhaust, just a deeper tone. I would like to remove the flapper to get rid of the restriction,  but this is completely  reversible at any time.

[HistoryTeacher2020]

Flapper removed along w/ OEM muffler. Kept rest of exhaust as in great shape. Installed Magnaflow. No drone. Tried Flowmaster 40, way too loud. 

[204Denali]

On 6/24/2020 at 4:10 PM, smald081 said:

Ok fellas here it is from someone who has actually done it. I Installed the Borla Atak muffler 2.5 off center inlet to center outlet. Off the top of my head part number was 400826... I tested the sound absolutely no drone with flapper valve removed. Then to further testing I covered the mesh resonators and love the sound now. Perfect no drone whatsoever. 2020 LT trail boss 5.3 muffler shop charged $100.00 got the muffler for 230 on sale for fathers day 

Does the 5.3 have only 1 flapper? and your saying your setup has zero drone? 

 

buddy was thinking of grabbing some exhaust mesh tape and covering the screens to see if it helps reduce the drone a little more 

Edited January 13, 2021 by 204Denali

[JohnH4260]

On 7/26/2020 at 9:27 AM, Ratchetarms said:

Stock exaust. Clamped flapper open.  Slight in crease in sound at startup.  No drone. After a while I covered all 6 screens.  Notable increase in sound at low rpms. Perfect for me. I haven't noticed any drone, even pulling a horse trailer. I know exhaust sound is completely subjective. I don't want a loud exhaust, just a deeper tone. I would like to remove the flapper to get rid of the restriction,  but this is completely  reversible at any time.

How did you clamp the flapper valve open?

[Ratchetarms]

Use two hose clamps. One on the inner piece and one on the outer piece with a piece of metal strap between the two. You must turn it open when tightening the clamps. Someone posted a picture, I will try and find it

Edited January 12, 2021 by Ratchetarms

[JohnH4260]

On 1/11/2021 at 8:49 PM, Ratchetarms said:

Use two hose clamps. One on the inner piece and one on the outer piece with a piece of metal strap between the two. You must turn it open when tightening the clamps. Someone posted a picture, I will try and find it

Thank you, I really appreciate it.

[JohnH4260]

Found this today on how to temporarily lock open the flapper. Photos included. 
https://static.nhtsa.gov/odi/tsbs/2014/MC-10137883-9999.pdf

[HighCountry MP]

2019 6.2 has two flappers no screens so im still wondering ? my 21 Tahoe has only 1 no screens id love to get my 6.2 to sound like that.

 

[dgstarr63]

What is a flapper? Why did GM spend the money to build it? 

[shakenfake]

I thought that the flapper was a sort of valve that opens up when you step on it sort of like an electric cut out but throttle activated.

 

Could be wrong though, that's what I thought I remember reading