Muffler Delete question

kkmitchell5 · January 5, 2017

Well guys back to the drawing board. it was still making that raspy whistle/hissy when driving under acceleration. No leaks and now the weep holes are welded over. They put it up on the lift to show me how the flapper affected noise, and confirmed they used 3 different pipe sizes... Then I had one of the mechanics drive it and one next to me listen to it and they all heard it and both determined it was the flapper. So after all that i absolutely ripped the guy for such shotty work and welding the weep holes. So now I'm back to square one, short a little bit of dough and have to take it somewhere else. So now i have a magna flow 18" muffler sitting at the house and I'm wondering what to do

GMC_SD_Ult_16 · January 5, 2017

Well guys back to the drawing board. it was still making that raspy whistle/hissy when driving under acceleration. No leaks and now the weep holes are welded over. They put it up on the lift to show me how the flapper affected noise, and confirmed they used 3 different pipe sizes... Then I had one of the mechanics drive it and one next to me listen to it and they all heard it and both determined it was the flapper. So after all that i absolutely ripped the guy for such shotty work and welding the weep holes. So now I'm back to square one, short a little bit of dough and have to take it somewhere else. So now i have a magna flow 18" muffler sitting at the house and I'm wondering what to do

Well I considered the following:

1. Getting another flapper off Ebay (if there) , check in with online salvage yards or calling multiple muffler shops in your area to see if someone left a flapper after having their truck or camaro done. I don't know if the camaro has the exact same flapper or not. I wasn't even aware that Camaros had a flapper until the forum member noted it.

2. Next was installing the expensive GM Borla system ($1,200 - $1,300) through the dealer. No drone and most liked the deep sound. Some feel it is not loud enough but my guess is for me it would be fine.

3. Get a tune or use the range device to turn off v4 and get rid of the flapper. You would have to play with the muffler to get the sound right but it would give you options. But many sounds on YouTube may help you choose.

These are the thoughts I was having if I ended up with flapper issues. I have heard from another forum member saying some of the Camaro owners had some flapper issues with springs etc... After finding another flapper it fixed their issue but you never know between vehicles how different it would be for the truck.

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kkmitchell5 · January 5, 2017

When the truck was on the lift they had a guy rev it up and it look like the flapper was functioning properly. I was thinking it may have something to do with the 6.2 (since i have 5.3) it would make a deeper sound as well as the larger piping that come along with it. Of course very well could be the flapper, but no way hell am i dropping 1300 for it and i told my self i wouldn't tune it until warranty it up and that the range device would be my last resort. Hopefully the next shop i take it to has much better insight with it.

Kens16Denali · January 5, 2017

Thanks for keeping us updated. I still plan on doing this once I finally get some free time.

Keep the updates coming.

bdbake01 · January 5, 2017

When the truck was on the lift they had a guy rev it up and it look like the flapper was functioning properly. I was thinking it may have something to do with the 6.2 (since i have 5.3) it would make a deeper sound as well as the larger piping that come along with it. Of course very well could be the flapper, but no way hell am i dropping 1300 for it and i told my self i wouldn't tune it until warranty it up and that the range device would be my last resort. Hopefully the next shop i take it to has much better insight with it.

Two things come to mind if the flapper is causing the sound. One, something odd about the actual flap itself. You would have to remove the piping to inspect. It's not unheard of for the actual flap/valve to become seperated from the stem. But this usually manifests as a rattle as opposed to a hiss.

The second, which could be more troublesome to diagnose, is simply the geometry of the setup you have now is introducing odd flow patterns for whatever reason. Multiple pipe sizes can do this as every time you change diameter of the pipe, the gases either speed up or slow down. Fluid mechanics. If this occurs at a junction point or INSIDE the flapper, I could see that causing problems. Is the pipe both before and after the flapper the same diameter?

GMC_SD_Ult_16 · January 5, 2017

When the truck was on the lift they had a guy rev it up and it look like the flapper was functioning properly. I was thinking it may have something to do with the 6.2 (since i have 5.3) it would make a deeper sound as well as the larger piping that come along with it. Of course very well could be the flapper, but no way hell am i dropping 1300 for it and i told my self i wouldn't tune it until warranty it up and that the range device would be my last resort. Hopefully the next shop i take it to has much better insight with it.

One other thought and maybe too much experimenting but what if you were to move the resonator back to its original location. My shop guy said the resonator is a tone adjustment tool and tends to take out higher pitched noises and allow the more desired lower tones. He said the GM resonator is fiberglass packed. What if it removed some of your flapper noise... I know it is opposite of what this thread discusses but I have heard many seemingly happy people with straight muffler deletes on YouTube as well. Just throwing that out as well.

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kkmitchell5 · January 5, 2017

Two things come to mind if the flapper is causing the sound. One, something odd about the actual flap itself. You would have to remove the piping to inspect. It's not unheard of for the actual flap/valve to become seperated from the stem. But this usually manifests as a rattle as opposed to a hiss.

The second, which could be more troublesome to diagnose, is simply the geometry of the setup you have now is introducing odd flow patterns for whatever reason. Multiple pipe sizes can do this as every time you change diameter of the pipe, the gases either speed up or slow down. Fluid mechanics. If this occurs at a junction point or INSIDE the flapper, I could see that causing problems. Is the pipe both before and after the flapper the same diameter?

That also crossed my mind. And who the hell know why but there is different pipe sizes. Before relocated resonator one size(new pipe) then flapper and maybe a foot and a half of original pipe then bend over axel different size(new pipe) then summit racing corsa style dual tip, different size. Also there was no flanges used, so all the new pipe is one size bigger that he slide over.

One other thought and maybe too much experimenting but what if you were to move the resonator back to its original location. My shop guy said the resonator is a tone adjustment tool and tends to take out higher pitched noises and allow the more desired lower tones. He said the GM resonator is fiberglass packed. What if it removed some of your flapper noise... I know it is opposite of what this thread discusses but I have heard many seemingly happy people with straight muffler deletes on YouTube as well. Just throwing that out as well.

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i have seen many of those youtube videos as well and dont seem to have any bad reviews of that sound under acceleration.

GMC_SD_Ult_16 · January 8, 2017

OK.. I felt there was a tick that was still not right today when I started the truck. It sounds good but something just not right so I had my son video while I got under the truck and opened/closed the flapper. . Unfortunately the tick is the flapper... Maybe my two previous leaks were masking or the cold just made it more apparent to me but after watching the video it was clear... Flapper open clean deep sound... Flapper closed still similar sound but a raspy background noise that just sounds annoying... Know I have to decide clean sound with drone in v4 and Hwy driving or no drone but a slight raspy noise at idle. Has anyone tried adding a small size bypass tube the way GM Borla exhaust did around its flapper? Just curious I doubt I will go there but I am going to be dealing with a sound I don't like at some point. I don't know how to shrink and load videos but I can tell you it is obvious of the difference. Thanks and let's keep trying to make these things sound better than stock.

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kkmitchell5 · January 9, 2017

OK.. I felt there was a tick that was still not right today when I started the truck. It sounds good but something just not right so I had my son video while I got under the truck and opened/closed the flapper. . Unfortunately the tick is the flapper... Maybe my two previous leaks were masking or the cold just made it more apparent to me but after watching the video it was clear... Flapper open clean deep sound... Flapper closed still similar sound but a raspy background noise that just sounds annoying... Know I have to decide clean sound with drone in v4 and Hwy driving or no drone but a slight raspy noise at idle. Has anyone tried adding a small size bypass tube the way GM Borla exhaust did around its flapper? Just curious I doubt I will go there but I am going to be dealing with a sound I don't like at some point. I don't know how to shrink and load videos but I can tell you it is obvious of the difference. Thanks and let's keep trying to make these things sound better than stock.

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Yep, I actually went a head and clamped my flapper open and it was gone. 3 inch hose clamp and 2 minutes and it makes the world of difference. I will say it is slightly louder and you do notice a different sound in v4. As far as drone in v4 it is very minimal, it is almost more of a rumble instead of drone.

GMC_SD_Ult_16 · January 9, 2017

Yep, I actually went a head and clamped my flapper open and it was gone. 3 inch hose clamp and 2 minutes and it makes the world of difference. I will say it is slightly louder and you do notice a different sound in v4. As far as drone in v4 it is very minimal, it is almost more of a rumble instead of drone.

I am considering moving the flapper in front of the resonator but having a bypass similar to what Borla used on their design to see if it fixes the chatter... For now I will leave the flapper clamped open but it is louder than I really wanted but certainly sounds better.

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kkmitchell5 · January 9, 2017

Yea its right at tipping point for me. Wife seems to like it and doesn't thinks its too loud, but at some point ill take it in to have them do it properly. But let me know what you figure out in the future!

Kens16Denali · January 9, 2017

Hmmm......all this has me thinking about sticking with my original plan and just swapping out the main

muffler with a 14" magnaflow, getting rid of the flapper but leaving the resonator. Also debating just

doing a muffler delete and flapper delete but leave resonator where it is. Keep the updates coming and

thanks for be the test subject for the rest of us.

kkmitchell5 · January 10, 2017

If I honestly had to do it all over again I would... do a muffler delete, keep flapper (can always clamp open), keep resonator and leave it where it is. If i did not like that i would then put shorter magna flow muffler keep resonator, keep flapper( again can always clamp open). That way would also be most cost and labor effective, especially if you dont move the resonator. I tried this because other members had success with it, but i also have 5.3 while others had 6.2...

GMC_SD_Ult_16 · January 10, 2017

If I honestly had to do it all over again I would... do a muffler delete, keep flapper (can always clamp open), keep resonator and leave it where it is. If i did not like that i would then put shorter magna flow muffler keep resonator, keep flapper( again can always clamp open). That way would also be most cost and labor effective, especially if you dont move the resonator. I tried this because other members had success with it, but i also have 5.3 while others had 6.2...

I agree with you kkm...I have the 6.2L and an MIT...The sound is overall good but on the high side of sound for me with the flapper open....with flapper closed I am getting a strange flutter sound at idle but completely fixes any drone type sounds. Anyway I will have to fix it over the next few weeks but for know will drive it to see how I feel. On a positive note as the temperature warmed up to 60 in Texas today the sound was somewhat less noticeable.

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Crstfr · January 10, 2017

man i'm still on the fence about exhaust.. so much reading.. so many choices.. so many configurations....!!!...i get nervous about the helicopter sound....... i mean i'd like to just cut it before the last cat, run 3 inch all the way back and dump before the axle ... .. but i'm stuck on the muffler... borla. .corsa, flowmaster, grrr... ..makes my head spin