2014 Used GT, how to make exhaust quieter and retune

Discussion in 'Mustang Chit Chat' started by ChosenJuan, May 9, 2021.

  1. ChosenJuan

    ChosenJuan Junior Member

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    I just purchased a 2014 GT and the exhaust is a little too loud for me, and there's also a rotten egg smell when I accelerate and also in the garage after driving. It's currently back at the dealer right now being inspected for an exhaust leak, but a mechanic friend of mine said it might also be tuned rich. From what the dealer said upon purchasing, it might have headers, but it has high flow cats and a Roush axle back exhaust (which I also had on my 17 GT).


    If there's no exhaust leak, what would you guys suggest to make the car a little quieter? Would I be able to get away with keeping the headers and high flow cats, but getting a quieter axle back (maybe MBRP, Borla Touring)? Or would I definitely have to go to stock headers and cats?


    Also, if there's no leak and it still smells like rotten eggs, would a retune fix that issue? I do have a local dyno tuner that I have gone to previously.


    Thank you. Right now my plan is to make sure there are no exhaust leaks, switch to a quieter axle back, and get the car retuned. Would like to hear thoughts from you guys. Thanks!
     
  2. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    First, welcome aboard. If there is no exhaust leak, but still have a rotten egg smell? it's more than likely your tune is running a bit on the rich side. If emissions inspection isn't a factor? you should be able to get away with keeping the headers and high-flow cats, otherwise, chances are your car will not pass OBDII emissions scan. If the sound of the exhaust is too loud for your liking? you can either add resonators, assuming the factory ones have since been removed or making the switch to a quieter axle-back like MBRP, Borla Touring or Magnaflow would be your best options IMHO. That being said, I would definitely have your car retuned if you still have the rotten egg smell with no exhaust leaks found :shrug:
     
  3. LarryJM

    LarryJM forum member

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    Borla sells a system to make your Mustang GT sound like a Ferrari. It was featured in a Jackson Barrett auction advertisement.
     
  4. ChosenJuan

    ChosenJuan Junior Member

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    I'm thinking of getting the Magnaflow Touring Catback to tame it down a bit.

    As for the rotten egg smell, provided there's no exh leak, how can I tell if its due to bad cats or due to the tune? I'm not sure what tune is on there right now, or if the previous owner retur ed to stock before trading in.

    As for emissions, will it not pass if tuned properly and not throwing a code? But I guess that depends from state to state, we don't have rollers here and they don't even look under the car. They just plug in OBD2 and check the gas cap
     
  5. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    The Magnaflow touring catback will definitely tame it down a bit. It was the same setup on my car until wanting something louder lol. Meanwhile, the warning signs of having bad cats are usually related to rattling/ticking noises followed by sluggish performance/acceleration, engine bogging down and the first sign is usually a check engine light.

    When the substrate materials such as ceramic break down/break apart, this leads to restricting the path of exhaust flow gasses causing them to clog up. Therefore the rotten egg smell is related to the clogging up of exhaust flow gasses. However, if you don't experience any of these warning signs, except for the rotten egg smell? then chances are it's from having a calibration tune which is way too rich. As for emissions, if your running high-flow cats? your car's ECM will throw a check engine light and code unless the rear 02 sensors are disabled in the tune. Also note that your car will not pass OBDII emissions scan if your rear 02 sensors are disabled/turned off in the calibration tube. If your running long tube headers? it most definitely requires a tune re-flash over stock as you cannot run long tubes on the stock tune. Anyhow, the best way to tell if your rotten egg smell is related to having bad cats or from having an improper tune? is by taking your car to a local dyno tuning shop and have them perform a complete diagnostic system test :shrug:
     
    Last edited: May 10, 2021
  6. ChosenJuan

    ChosenJuan Junior Member

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    Thanks for all that! I'm thinking of taking it to my local exhaust shop that does all my cars so they can inspect the headers and cat to make sure its all in good condition with no leaks, and maybe even weld in some resonators or install a quieter exhaust.

    I have a local dyno tuner as well that worked on my 17 GT so I should probably go to them if the exhaust is in good order. The dealer did say emissions testing was performed and passed a few weeks ago, and it shows that too on the carfax. I'll just jack the car up myself and see whats under it
     
  7. LarryJM

    LarryJM forum member

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    Just one tankful of leaded race gas will do the trick on cats.
     
  8. DieHarder

    DieHarder Member

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    I have a set of 2013/14 original exhaust piping and OEM mufflers if you need them. PM me if you're interested.
     
    Robert302 and ChosenJuan like this.
  9. eighty6gt

    eighty6gt forum member

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    Do this.
     
    Robert302 likes this.
  10. Robert302

    Robert302 Junior Member

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    This would be a good option if the car is too loud. I have OEM mufflers on my car and I think they sound decent.
     
  11. OX1

    OX1 forum member

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    This. Stock quiet and I was still able to trap 125 through totally stock exh.
     
  12. Enfield

    Enfield Member

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    Also running stock mufflers behind LTH's and catless X. Sounds good when stomped. NA.
     
  13. 2007black

    2007black Junior Member

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    Borla Touring, axle back, worked for me.[​IMG]
     
  14. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    Or go with the Ford Racing version which is also manufactured by Borla.
     
    ChosenJuan likes this.
  15. Mike in SC

    Mike in SC Lactation Consultant

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  16. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    Last edited: May 13, 2021
  17. Juice

    Juice forum member

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  18. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    Just to make certain we're on the same page, are you referring to actual high-flow catalytic converters or rear O2 mini cat, non-fouler extenders?
     
    Last edited: May 14, 2021
  19. Juice

    Juice forum member

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    Actual high flow cats. Flomaster universal 3 way, 3 inch pipe.
    I dont use those cheaters btw.
     
    06 T-RED S/C GT likes this.
  20. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    Okay, thanks for clarifying :waytogo:
     
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