Exhaust Flapper , mod?

[SquireSCA]

Maybe the DFM on the 5.3 sounds different than on the 6.2?  Mine, you can hear it,  but it is very subtle and doesn't sound like a helicopter...

[Scooter Scott]

This is a great question that I am looking for an answer too.  I have a 2019 6.2 and have held off to see what others are experiencing.  People don't understand the mesh screens aren't on the 6.2 but keep commenting on threads about 6.2s on how to fix them....

[MG386]

I have the 6.2 and the GM Cat back. I don't understand what people are talking about with this helicopter sound. I've driven 40-50 and all speeds windows up/down everything, and I can't get it to make any abnormal sound.

I'm just curious because I kept both my resonators just in case I need to put them back on to quiet it down, but I don't hear anything.

Are you towing while doing this?

Sent from my Pixel 4 XL using Tapatalk

[DaveHC]

On 12/29/2019 at 5:15 PM, Londart2020 said:

I have the DFM too, and the heli sound come from when goes to two or less cylinders. Anybody have any input on getting these put back on?

from what I have read, resonators handle the drone, cans on 6.2 and screens on 5.3 do the same job of cancelling it out on the stock exhaust, most cat backs don't have them and many say no drone so not sure how it works on them.

Edited January 28, 2020 by DaveHC

[snork]

went and relocated the spring tension to keep flapper open

[Texasdeere]

 

Interested in seeing how this sounds on my truck when disabled

 

 

Edited January 29, 2020 by Texasdeere

[Dick Messerly]

On 12/28/2019 at 4:33 PM, michael betz said:

Best mod ever.  Love it. Highly recommend the Borla atak. No drone. Perfect sound. Not too loud ,not quiet. Perfect 

Had the ATAK on my 2017 5.3L and I truly miss it. Did you just throw the ATAK muffler on or is it the whole system? If it's just the muffler where did you get it at I asked borla and they told me they wouldn't sell the muffler only. 

[Texasdeere]

Flapper pinned open, stock 5.3 single exhaust so far maybe a 5% increase in sound.  No undesirable noises.  Going to put some miles on it to make sure.

[JohnH4260]

On 2/2/2020 at 12:51 PM, Texasdeere said:

Flapper pinned open, stock 5.3 single exhaust so far maybe a 5% increase in sound.  No undesirable noises.  Going to put some miles on it to make sure.

How did you pin the flapper valve open? Thanks.

[flyingfool]

....

Edited January 13, 2021 by flyingfool

[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

[Texasdeere]

I just used a metal hose clamp but that looks way more professional!

 

Looking back it was more like a 10% increase in sound. Quite noticeable on cold start up.  You could hear it more when you "got on it"  Just right for me.

[SilveradoVictory]

Any noticeable change in fuel use or power? I would think that opening the valve would allow the exhaust gasses to flow more easily and therefore more efficiently clear out the cylinders on the exhaust stroke.  Does moving those gasses quicker increase the mileage or the horsepower?