Magnaflow Muffler On the 6.2

truck_newbie · August 18, 2019

Replaced the stock muffler with the Magnaflow 11229 which has 3” in and out. Initially, the exhaust shop removed both flappers. It sounded very deep and rumbly but a bit louder than I preferred. The drone especially on the highway was unbearable.After emailing Magnaflow support, they recommended I have the shop put the flappers back on so I had both flappers welded back in. The flappers completely eliminated the drone but did quiet down the muffler quite a bit. Now, it’s about 70% as loud as the GM performance exhaust which is the perfect level of loudness I was aiming for. I didn’t want anything obnoxious. Sounds really good when you put your foot in it. Cold start (attached) is equally as lively.

If you find the GM performance exhaust a bit too loud for you, then this mod will be the perfect volume level. Just save yourself the headache and money by having the shop install the flappers from the get go. Cost me $220 for muffler and install. $80 to weld the flappers back in. All in all, very pleased with it.

fish_guru · August 19, 2019

Sounds good.

I wonder if removing one flapper and leaving the other one would get you to where you want it. But then the question would be, which flapper? Before the muffler or after?

To flap, or not to flap, that is the question.

truck_newbie · August 19, 2019

37 minutes ago, fish_guru said:

Sounds good.

I wonder if removing one flapper and leaving the other one would get you to where you want it. But then the question would be, which flapper? Before the muffler or after?

To flap, or not to flap, that is the question.

Hahaha, you must have read my mind. Had this same exact thought after they welded back in the 2 flappers. Definitely 1 flapper will give you more sound than 2 but the question is, which one would kill the drone. My suspicion without any evidence is flapper after the muffler will kill the drone.

Definitely going without both flappers is an absolute no-no for drone as i found out the hard way. Alternatively, a j-pipe without the flappers will also kill the drone and give you full sound but that requires experimentation and could get expensive if it takes multiple tries to tune it correctly. At that point, you might as well spend more and go for the full cat-back system.

Very happy with this setup though. Sounding better and better as muffler and truck both break-in.

brianc636 · August 19, 2019

Replaced the stock muffler with the Magnaflow 11229 which has 3” in and out. Initially, the exhaust shop removed both flappers. It sounded very deep and rumbly but a bit louder than I preferred. The drone especially on the highway was unbearable.After emailing Magnaflow support, they recommended I have the shop put the flappers back on so I had both flappers welded back in. The flappers completely eliminated the drone but did quiet down the muffler quite a bit. Now, it’s about 70% as loud as the GM performance exhaust which is the perfect level of loudness I was aiming for. I didn’t want anything obnoxious. Sounds really good when you put your foot in it. Cold start (attached) is equally as lively.

If you find the GM performance exhaust a bit too loud for you, then this mod will be the perfect volume level. Just save yourself the headache and money by having the shop install the flappers from the get go. Cost me $220 for muffler and install. $80 to weld the flappers back in. All in all, very pleased with it.

Maybe I’m wrong but it looks like you choked the system down to 3” to go into the muffler then necked it back up to tie it back in. Why not get a 3.5” muffler to prevent this?

truck_newbie · August 19, 2019

11 minutes ago, brianc636 said:

Maybe I’m wrong but it looks like you choked the system down to 3” to go into the muffler then necked it back up to tie it back in. Why not get a 3.5” muffler to prevent this?

The shop provided the muffler. The owner seemed very knowledgeable and considering i'm no exhaust expert, i trusted his judgement. I did some more research after the fact and the consensus i got was, after a certain diameter, going bigger is actually worse.

PS. I thought the factory piping was 3". Are you saying it's 3.5"?

brianc636 · August 19, 2019

The shop provided the muffler. The owner seemed very knowledgeable and considering i'm no exhaust expert, i trusted his judgement. I did some more research after the fact and the consensus i got was, after a certain diameter, going bigger is actually worse.

PS. I thought the factory piping was 3". Are you saying it's 3.5"?

My exhaust on my 6.2 (GMPP exhaust) is 3.5 based on circumference measurements. Looking at your pictures, if a 3” muffler was installed, the piping for it is definitely smaller than the piping before and after it.

truck_newbie · August 19, 2019

5 minutes ago, brianc636 said:

My exhaust on my 6.2 (GMPP exhaust) is 3.5 based on circumference measurements. Looking at your pictures, if a 3” muffler was installed, the piping for it is definitely smaller than the piping before and after it.

Oh, ok, That's interesting. Yeah, the muffler is definitely 3" in and out.

How are you liking the GMPP exhaust? Before going this route, i went back to the dealer to test drive a truck with it installed. I didn't love it as much as i did when i was purchasing my truck. I love the fact it has absolutely no drone but when you put your foot in, i felt it was a little too high pitch. Personally, i prefer a little more deep rumble.

brianc636 · August 19, 2019

It’s not bad actually. It’s extremely quiet going down the road but has a nice tone going down the road.

I wish it was a little louder (hence my decision to install a dynomax muffler later) but it has zero drone at highway speeds.

truck_newbie · August 19, 2019

That's cool. I think i might install a cat-back system down the road. It will probably be the Borla Touring. Unfortunately, i'm not able to find any sound clips of the Touring, only the Type-s. General feeling i'm getting from here is the type-s is fairly loud.

PS. I think the flappers are starting to squeak so the cat-back system might not be too far in the future. Maybe i need to find some high temperature lube for the flappers after i verify the squeaking is not coming from the engine belt.

brianc636 · August 19, 2019

I just ordered my dynomax muffler 17517.

If it sounds like I hope it does (used the on my 96 impala ss with a 383) I’ll sell my GMPP muffler in the market place.

truck_newbie · August 20, 2019

1 hour ago, brianc636 said:

I just ordered my dynomax muffler 17517.

If it sounds like I hope it does (used the on my 96 impala ss with a 383) I’ll sell my GMPP muffler in the market place.

Post a sound clip when you have it installed.

OnTheReel · August 20, 2019

The flappers are probably a much more substantial bottleneck than the 3” muffler when it all comes down to it.

Sounds good though. I have the GM performance exhaust and I was really surprised how rowdy it is for an “oem” type part. I’ve grown to love it though.

brianc636 · August 20, 2019

The flappers are probably a much more substantial bottleneck than the 3” muffler when it all comes down to it.

Sounds good though. I have the GM performance exhaust and I was really surprised how rowdy it is for an “oem” type part. I’ve grown to love it though.

Agree. The oem GMPP exhaust isn’t bad at all. I’m just wanting a bit more sound but not too much and definitely don’t want the drone. Good news is with Dynomax, if you’re not happy with the muffler, they’ll refund your money for it. All I’m out is about 35.00 for some stainless piping and time if it doesn’t work out.

With it being a stainless system, I’ll take it to work and have the shop guys tig weld an extension to the factory head pipe and clamp the muffler in. If it doesn’t work out, I’ll cut the pipe at the weld and bolt the factory muffler back in. Pretty easy solution, IMO at least.

truck_newbie · August 20, 2019

22 minutes ago, OnTheReel said:

The flappers are probably a much more substantial bottleneck than the 3” muffler when it all comes down to it.

Sounds good though. I have the GM performance exhaust and I was really surprised how rowdy it is for an “oem” type part. I’ve grown to love it though.

Right on. With the flapper fully opened, the hole is only about two-thirds unobstructed. Honestly, before i had the flappers welded back in, I didn't notice any seat of the pants difference in power. The drone was just hard to take.

MAK2013 · February 4, 2020

I’m adding the Magnaflow 11229 this week. I’m just so confused about the flappers. Clearly both off will cause too much drone. I want to remove one of them but that begs the question... which flapper is the right one to keep in order to prevent drone?! I’m thinking it’s most likely the upstream (before muffler) flapper that needs to stay but, again, I’m not positive. Anyone had any lucky recently with the flappers?