2014+ Exhaust Systems & Mufflers

Kevin King · June 4, 2019

Is it possible to run the flapper valve on an aftermarket exhaust?

if not what are the best ones out there that don’t make v4 sound like your truck is dying? Or even some that include one?

3tspapat · June 4, 2019

The GMPP Borla comes with the flapper valve. I haven't had any issues with crazy weird noise when in V4.

You can also have someone weld the stocker back on there.

Mileguru · June 9, 2019

Does the Magnaflow 12909 stay 3.5" all the way through the muffler, or does it bottleneck down?

I plan on using this muffler and will definitely cut out the flapper. Should I also cut out the resonator or leave the resonator in? I don't mind a little noise, but I don't want a LOUD system. From what I've read, it doesn't seem like deleting the resonator while using the 12909 will be all that loud.

michigan2500hd · June 9, 2019

On 6/4/2019 at 3:03 PM, Kevin King said:

Is it possible to run the flapper valve on an aftermarket exhaust?

if not what are the best ones out there that don’t make v4 sound like your truck is dying? Or even some that include one?

I have the Magnaflow 12909 I believe. ( The one for the 6.2 liter)

Just removed the stock muffler and welded this in it's place. Left the flapper valve in it. With the flapper operational it's hard to tell much of a difference from inside the truck. Pinned the valve open and it sounds much better. I left the resonator on because I was afraid it would be too loud.

I then tried a MBRP cat-back and it sounded really good but ended up being a little too loud, especially when towing a heavier trailer. Went back to the Magnaflow.

Had the girlfriend use the truck while I listened from the driveway and it sounds great. Deep, powerful sound but in no way loud. Sounds more like the 93-97 Camaro LT-1 with a nice rumble.

Kevin King · June 10, 2019

8 hours ago, michigan2500hd said:

I have the Magnaflow 12909 I believe. ( The one for the 6.2 liter)

Just removed the stock muffler and welded this in it's place. Left the flapper valve in it. With the flapper operational it's hard to tell much of a difference from inside the truck. Pinned the valve open and it sounds much better. I left the resonator on because I was afraid it would be too loud.

I then tried a MBRP cat-back and it sounded really good but ended up being a little too loud, especially when towing a heavier trailer. Went back to the Magnaflow.

Had the girlfriend use the truck while I listened from the driveway and it sounds great. Deep, powerful sound but in no way loud. Sounds more like the 93-97 Camaro LT-1 with a nice rumble.

Oh nice so it doesn’t really mess with it. I had a 16 with a Black Widow which I loved just wasn’t a fan of the V4 mode. Not the mufflers fault but I didn’t keep the flap on when I switched it over. Now with my new truck I was going to get the same exhaust but wondered if leaving the flapper on fixed the weird v4 noise.

michigan2500hd · June 10, 2019

4 minutes ago, Kevin King said:

Oh nice so it doesn’t really mess with it. I had a 16 with a Black Widow which I loved just wasn’t a fan of the V4 mode. Not the mufflers fault but I didn’t keep the flap on when I switched it over. Now with my new truck I was going to get the same exhaust but wondered if leaving the flapper on fixed the weird v4 noise.

Even with the flapper pinned open I don't get the helicopter noise. I can tell it's in v4 most of the time but it's not at all intrusive like it was with the MBRP cat-back. I can't imagine anyone being bothered by it.

Racindave · June 25, 2019

On 6/4/2019 at 2:03 PM, Kevin King said:

Is it possible to run the flapper valve on an aftermarket exhaust?

if not what are the best ones out there that don’t make v4 sound like your truck is dying? Or even some that include one?

I left the flapper in mine with flowmaster 50 and dual tail pipes.

Edited July 16, 2019 by Racindave

Kevin King · June 25, 2019

1 hour ago, Racindave said:

I left the flapper in mine with flowmaster 50 and dual tail pipes.

How does it sound on v4?

Racindave · June 25, 2019

11 minutes ago, Kevin King said:

How does it sound on v4?

Can’t tell any difference whatsoever

Racindave · June 27, 2019

On 6/25/2019 at 2:40 PM, Kevin King said:

How does it sound on v4?

Just FYI. I went back and pinned the flapper open yesterday and there is definitely a helicopter sound. I wouldn’t want to run it in v4 without the flapper.

jimbrown1 · June 29, 2019

So I purchased the Borla 400130 back in March 2019 just after purchasing my new Sierra (2018) from the dealer in February. The sound was not at all like the GMPP muffler produced by Borla, and was discontinued under the GMPP part number. Borla said they continued to get requests for this muffler and began producing it again, but it's not $75 any more, it's $200. With that being said, the muffler seemed to not be the same as the GMPP I had installed on my 2011 Silverado. Borla said the packing materials and design are a little different than before and you had to put some miles on it to break it in, probably around 800-1200. Well, I did that, and no change. The next thought was the resonator behind the rear axle is muffling the sound so I went to Aces Performance Exhaust this morning to just have them cut that out and leave the rest as is. It's not as loud on start up as a Corsa cat back(14848) for sure. I had no drone in the cabin and you can definitely hear it in the cabin now when accelerating whereas before it was very, very muffled. I can only upload a video of 4.88MB and both files exceed that.

Todd1982 · July 14, 2019

Anyone have the torque specs for the following items after header install .

Steering shaft bolt

Transmission Cross member bolts

Transmission mount nut

Thanks

00pooterSS · July 19, 2019

On 6/9/2019 at 12:54 PM, michigan2500hd said:

I have the Magnaflow 12909 I believe. ( The one for the 6.2 liter)

Just removed the stock muffler and welded this in it's place. Left the flapper valve in it. With the flapper operational it's hard to tell much of a difference from inside the truck. Pinned the valve open and it sounds much better. I left the resonator on because I was afraid it would be too loud.

I then tried a MBRP cat-back and it sounded really good but ended up being a little too loud, especially when towing a heavier trailer. Went back to the Magnaflow.

Had the girlfriend use the truck while I listened from the driveway and it sounds great. Deep, powerful sound but in no way loud. Sounds more like the 93-97 Camaro LT-1 with a nice rumble.

I have a little test spot where I test mods. When I replaced my muffler with a magnaflow and removed the cutout at the same time I gained 3 mph and after that I saw an increase of a couple of mpg too.

I gotta ask, why would you choose to keep the flapper, it's a pretty big restriction and makes adding in a free flowing muffler pointless.

michigan2500hd · July 19, 2019

Because of previous experiences of adding a louder muffler and the helicopter sound of the 4cyl. mode I wanted to have the flapper if needed. I pin mine open now so I can't imagine it's restriction is too large. I would have removed it if I knew it wouldn't be needed. Which it's not. I added the Magnaflow for the sound not really for the power gain which is small anyway. The 6.2 has plenty of power and I bumped up the throttle sensitivity so take offs are much more enjoyable.

00pooterSS · July 19, 2019

Gotcha. BTW I gained the 3 mph and mpg vs having the flapper wedged open with the stock muffler, and then went to the magnaflow and cut out the flapper.

That sucks about the v4 helicopter sound, but if you have it wedged open and are fine with it then sounds like you'd be okay getting rid of it. Maybe take the flapper home and keep it in case you want it put back in.

I just personally hate the idea of having the flapper after taking a good look at it after it was cut off. Even wedged open it takes up a considerable amount of space in the pipe.

Your truck your thing, just tossing out my experience with removing it and looking at it in my hand and thinking holy crap, even open, that's a big restriction. (keep in mind the restriction to flow wont just be from the physical size of the flapper, but also restriction of air trying to get around it and the disturbance in flow, add the physical size and the flow restriction together, makes for quite a bit of a restriction)

Edited July 19, 2019 by 00pooterSS