AFM and DFM Flappers

DuRsT · February 10, 2020

Ok, after reading multiple threads I believe that I have gathered that removing flappers from an AFM enabled truck would result in the helicopter type sound, but on the DFM trucks removing the flappers only results in additional drone.

Is this accurate?

SquireSCA · February 10, 2020

True on AFM, not quite true on DFM. Removing the flapper really doesn't produce drone, its FAR less perceptible than the helicopter sound on the AFM motors...

I removed mine on my DFM motor, along with the muffler itself, and no real drone so long as you leave the resonator screens intact. I have a video posted somewhere here of it.

DuRsT · February 10, 2020

26 minutes ago, SquireSCA said:

True on AFM, not quite true on DFM. Removing the flapper really doesn't produce drone, its FAR less perceptible than the helicopter sound on the AFM motors...

I removed mine on my DFM motor, along with the muffler itself, and no real drone so long as you leave the resonator screens intact. I have a video posted somewhere here of it.

I have the 6.2 in my SLT so I believe mine has actual resonators instead of the screens. I'm supposed to be getting a Magnaflow 11229 installed on Friday and am toying with the idea of just having all flappers removed.

Texasdeere · February 10, 2020

I've been toying with my stock 5.3 single side exhaust lately. First I pinned open the flapper, this added a slightly deeper tone, especially on start up. No drone and no womp, womp sound at 40 to 50 mph. Overall about a 10% increase in sound. It is very slight but after you drive around for a few days you notice the slight increase in volume. Completely removed I'm sure it will go up a tick more.

Next I added a 3" full tailpipe, ( no screens) flapper still open. I was actually shocked at how good the stock muffler sounded! For me it was the perfect volume. It was a nice deep sound. It sounded about the same as the GMP/Corsa 3" system but at 40% of the volume, not rowdy and overwhelming. So with the mesh screens gone I could hear the womp womp sound but it really wasn't that bad and besides I hate driving 40 to 50 mph anyway.

I put the stock tailpipe back on and decided to go the quiet route after all. But I am going to have the flapper section completely removed soon. I think the flapper itself is a pretty major restriction at WOT even pinned open.

The 6.2 is a different animal all together. I wonder how a 6.2 would sound with just the flappers removed?

DuRsT · February 10, 2020

Have to agree, the 6.2 having a larger displacement and different exhaust setup from the factory makes it a little different.

I'm wondering if using an 11229, no flapper, and leave the resonators would result in a fair amount of (good) volume without the drone or undesirable DFM related noises. We may just find out on Friday unless I wimp out and get the quieter 12589 Magnaflow.

snork · February 11, 2020

7 hours ago, DuRsT said:

Have to agree, the 6.2 having a larger displacement and different exhaust setup from the factory makes it a little different.

I'm wondering if using an 11229, no flapper, and leave the resonators would result in a fair amount of (good) volume without the drone or undesirable DFM related noises. We may just find out on Friday unless I wimp out and get the quieter 12589 Magnaflow.

Do the straight pipe minus both the flapper for the 6.2 and retain the resonators

SquireSCA · February 18, 2020

On both trucks, the resonators change the harmonics and resonance of the exhaust and keep the droning at bay... You can remove the muffler and flapper and it will sound great.

greco2003 · February 18, 2020

I had my single flapper removed on my 2019 5.3L Silverado. I need to get the resonators closed up now. I used a magnaflow muffler sounds great but not much louder then stock unless your on it

https://www.amazon.com/gp/aw/d/B000XQM1JE?psc=1&ref=ppx_pop_mob_b_asin_title

MAK2013 · February 20, 2020

On 2/10/2020 at 10:43 AM, DuRsT said:

I have the 6.2 in my SLT so I believe mine has actual resonators instead of the screens. I'm supposed to be getting a Magnaflow 11229 installed on Friday and am toying with the idea of just having all flappers removed.

I have the 11229. I tried removing both flappers on my 6.2. Ended up having them weld the upstream flapper back in. It was horrifyingly annoying with both off, it literally sounds like a Blackhawk is flying under your truck. At 65 mph with the upstream flapper it still drones, but not horribly. Without it there was a constant “wah wah wah” noise at any speed over 35. I highly recommend you keep the upstream (before muffler) flapper intact. And yes, you’re correct, the 6.2 has true resonator while the 5.3 has those screens

MAK2013 · February 20, 2020

On 2/10/2020 at 12:09 PM, DuRsT said:

Have to agree, the 6.2 having a larger displacement and different exhaust setup from the factory makes it a little different.

I'm wondering if using an 11229, no flapper, and leave the resonators would result in a fair amount of (good) volume without the drone or undesirable DFM related noises. We may just find out on Friday unless I wimp out and get the quieter 12589 Magnaflow.

This is with the upstream flapper and the 11229. Resonator left in place as well

11229 with upstream flapper