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  1. #1
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    Unique S55 exhaust sound solution

    Hi all,

    I haven't posted a whole lot on here after I unloaded my S5 (thanks sticky for featuring me in audiboost for a few of my 10 second runs in it!). I picked up a 2019 M4cs a few months back and loving every minute of it, even enough to stay stock for now.

    One thing that bugged me, I never fully enjoyed the S55 exhaust note, not even with singular mids or double x-pipe mids, there was something always off and buzzy sounding about them and it didn't seem like it was ever revving high like a sports car should (or like a classic inline-6 should sound like).

    Upon going over pictures, I noticed that the S55's downpipes are unequal in length, with a difference of over a foot between front and rear banks. They follow the same bends independently until they reach the center resonator, which has a built in H-pipe where the finally merge. But because the pipes never get an opportunity to even out in length, the H-pipe only serves to balance out exhaust pressures, but never to balance out an inline 6's naturally equal spaced exhaust pulses. Essentially, all exhaust solutions on the market only serve to amplify that S55 noise, but never changes the actual character of the sound to make it more of a traditional inline 6 sound, because the S55 exhaust set-up is naturally unbalanced length-wise.

    I have been discussing on the other forum on solutions to this. What is the solution I decided to take you ask? Well, I decided to equalize this difference in length as much as possible before it merges at a new X-pipe or H-pipe location.

    I did just that:

    -stock downpipes (all cats intact)
    -stock midpipes (all cats intact)
    -center resonator/H-pipe delete
    -revised rear section piping adding a "U-bend" on the passenger side (compact and effective given the tight area)
    -merge both driver and passenger pipes to a custom H-pipe (placement is now between the rear diff and OEM muffler).
    -all piping goes back to an OEM muffler (CS muffler, not sure of the difference).

    Here is the result (cellphone video, sorry for quality). I am going back for "version 2" to replace that custom H-pipe with a custom X-pipe. Spacing is tight, so no off-the-shelf x-pipe will work. The S55 as been in the US market since 2015, this is one of the 1st set-ups of this kind ( 2 others exist only because of behind the scenes discussions with other board members).

    It's a different sound to what you are used to in an S55, but the pitch-change as it revs completely changes the character of the S55, it sounds like it loves to rev now. Anyway, this is only version #1 , the H-pipe is spaced too far to effectively smooth out the sound completely, but hopefully that X-pipe will resolve it when it goes back in soon. Updated videos will come once that's installed.

    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  2. #2
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    sorry guys, i just realized I posted this in the wrong section of the forum!

    But here is another video of the audio only (the sound sorta sucks I know with the wind noise)

    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  3. #3
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    Do you have any pictures of the actual exhaust?

  4. #4
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    Yes, ill post the finalized version

    Here is a better audio clip part throttle. Full throttle induced too much distortion from my mic, and the audio tends to clip.

    https://drive.google.com/file/d/1KGO...w?usp=drivesdk
    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  5. #5
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    a drawing of whats done, version 2 now crosses over with an x-pipe vs an h-pipe (terrible drawing I know...), basically the U-bend is a compact way to add length in a tight space, once the pipes are close to equal on both banks, merge them at a crossover, in my case its now behind the rear differential. The RED in the drawing is what is new:

    Click here to enlarge

    and the new video of the equal-length pipes + x-pipe in action:

    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  6. #6
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    And a quick part throttle in 1st gear up to
    4,500rpm

    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  7. #7
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    More videos with equal-length + x-pipe

    Comparison stock, stock with single AA mid-pipe, stock with equal-length pipes



    And this one:

    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  8. #8
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    Sounds 1000% better. Surprised more people aren't looking into this.

  9. #9
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    Exactly what the S55 needs!

  10. #10
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    unfortunately these are currently all custom because nothing in the aftermarket has stepped up to create their own version.

    This guys before/after captures a better angle at how different equal-length exhausts can sound like (slightly raspy, but he is catless on both of the videos), sounds almost like an S54 with Euro headers after:




    This guy took it a step further and used an aftermarket muffler instead of the OE muffler:



    You basically need to offset the passenger side downpipe being shorter (approx 14-15") somehow before they merge. None of the pipes on the market correct this, so the S55 sounds the way it does because of it. If you add the 14-15" back to the passenger side, and then merge them, you'll create a classic straight 6 noise and not having 2 inline 3 exhaust notes.
    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



  11. #11
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    1 out of 1 members liked this post. Yes Reputation No
    looks like the aftermarket is finally catching on..

    Loe P.
    - 14' B8.5 Audi S5 3.0"T" S-tronic
    - 09' E90 M3 7-DCT Interlagos Blue / Novillo Silver - gone Click here to enlarge



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