Magnaflow 12909 vs OE

Discussion in 'Performance' started by Shadow17, Oct 2, 2017.

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  1. Shadow17

    Shadow17 Full Access Member

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    I still have the OE muffler on my Denali with the butterfly valve open.
    Opening the valve helped add more sound but does require me to drive in M7 since the AFM is now more audible. This will be no big deal after my BB tune.

    Question- from watching videos is doesn't appear the Magnaflow really changes much of anything. I know the muffler is only $125, but labor will without doubt be 1-2x that to have it installed.

    Those of you that have done the change, was it worth $300 +/-?

    *UPDATE- quote I was given is $275 for muffler install and oil change. No clue if that is fair being how every oil change until now has been free and the shop doing the install is ballparking the estimate.
     
    Last edited: Oct 4, 2017
  2. CMoore711

    CMoore711 TYF Newbie

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    Great question as I've been looking into this as well. Really wanting to add some additional sound to my '15 Denali XL and get rid of the factory exhaust flapper valve. My previous daily was a Trailblazer SS with 1-7/8" Kooks longtubes and an SLP Powerflo exhaust and I loved the sound. Unfortuntely SLP doesn't offer an 3.5" In/Out muffler, they do offer an exhaust system for the Sierra/Silverado that sounds really good, but its only 3".

    I've also been considering doing this muffler swap with a Borla XR-1 Part# 40946: https://www.borla.com/products/xr1_...er_16x45x788__racing_muffler_part__40946.html

    The Borla XR-1 muffler is a bit more expensive, but I agree with you, from videos I've watched the Magnaflow 12909 doesn't seem to change much, and in the video below the change in exhaust tone and sound seems to be a bit more noticeable.

    This is the closest comparison video I have found that would give an idea of sound. Keep in mind this is a 2012 GMC with 6.2 so it's not the current DI 6.2 motor we have but should be "comparable" in sound:
     
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  3. Shadow17

    Shadow17 Full Access Member

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    Well I'm going to go ahead and give it a shot.
    Where exactly is the resonator? I read to remove the butterfly valve, but not the resonator. Want to make sure I give them the correct info.
     
  4. NORCAL SS

    NORCAL SS SUV SUSPENSION GURU Supporting Vendor

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    ive installed the 12909 on many 15 ups. i sell the muffler also cheaper then summit or jegs.

    When i install on customers rigs ill do the muffler and the keep the resonator which is at the rear bumper area.

    Upon changing the mufffler i tell them to wait about 2 weeks for it to break in and if they want it louder come back and i remove the butterfly valve.

    My escaldade has 1 7/8 headers/supercharged/magnaflow 3.5 cat back with the resonator cut off and it sounds great
     
  5. jl449

    jl449 Full Access Member

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    I did the 12909 and buttlerfly removal on my Denali 15i. Also did the AFE intake. All from Norcal as he had the best price.
    I think I paid 150 bucks for the muffler install and butterfly removal.
    The truck sounds mean and love the performance. Best bang for the buck IMO The stock pipe is already 3.5".
     
  6. Shadow17

    Shadow17 Full Access Member

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    This is good to hear. these are the same mods plus BB tune that I am looking to do.
    I'm not trying to turn my Denali into a performance vehicle, just trying to make it a bit more exciting to drive.
     
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  7. Shadow17

    Shadow17 Full Access Member

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    Well, just got the Denali back.
    It sounds oh so nice! It gives the Denali a truck sound now and not so hushed down.
    From factory I was extremely disappointed with the sound of the exhaust. I can't imagine what all these ecoboost guys are doing for sound.
    When I opened the butterfly valve it improved the sound. But left me wanting to hear more.
    The 12909 with butterfly removal is perfect, for me. It sounds great when started, and just as good upon acceleration.
    I always drive in M7 to eliminate AFM so it sounds perfect while cruising. You barely hear any exhaust noise. There is just a slight deep tone to let you know there is a V8 under the hood.
    I would assume it might be a bit annoying in V4 mode as it louder than with the OE muffler and butterfly valve pinned open.
    I paid $126 to have the muffler installed and $12.54 for 6" of 3.5" pipe.
    FWIW, the exhaust pipe is stainless before the muffler; aluminum after from factory.
     
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  8. CMoore711

    CMoore711 TYF Newbie

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    Nice. Good update and feedback. Also, good info on the difference in exhaust pipe material.
     

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