This will change S55 exhaust sound market forever

Discussion in 'F80 M3 Saloon / F82 M4 Coupe / F83 M4 Convertible (2014-present)' started by zedtom3, Jan 12, 2020.

  1. 16 Jan 2020 at 5:15 PM #61
    DeadEye

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    Last edited: Jan 16, 2020
  2. 16 Jan 2020 at 5:16 PM #62
    wkdtime

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    I know I’m in the minority, but I don’t get the exhaust thing with the F80/F82, I don’t get why it gets such a bad rep for an in-line 6.

    I’m talking about the sound that comes out of the back of the exhaust and not the noise in the cabin or under the hood.

    I’m saying this after owning a Supra TT, E46 M3 and an R35 GTR.

    Compared to those cars, out the box, stock vs stock my F82 which has the OPF filter sounds better than either of those cars stated above.

    The worst for sound for me was the E46, I absolutely hated the tinny rasp which sounded like it had a pea shooter exhaust.

    I understand it’s all subjective, I’ll be honest, when seeing YouTube videos the M4 sounded really shite, but in person, at least for me, it sounds so much better, the pops and burble on over run etc.
     
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  3. 16 Jan 2020 at 6:20 PM #63
    ZeroFX

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  4. 16 Jan 2020 at 6:54 PM #64
    DeadEye

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  5. 16 Jan 2020 at 9:23 PM #65
    Moonstone

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    Don’t get all the fuss. Cars are sounding sh1tier and getting quieter each generation and with electric coming in, as these cars become rarer on the road the even the most subdued exhaust is going to sound over the top.

    I watched all the videos above and none of them really sound any better than the other to my ears. I see a lot of people spending a lot of time and money for only marginally different outcomes. It’s really not worth all the hassle in my opinion. If you want a car that sounds as good as an E92 M3....buy an E92 M3.
     
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  6. 17 Jan 2020 at 9:11 AM #66
    DeadEye

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    I've been looking at them... An E92 with Akra sounds fantastic.
     
  7. 17 Jan 2020 at 7:42 PM #67
    Doughboy

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    M2 has N55 single turbo (twin scroll single shaft, but still merged to one exhaust at turbo outlet. Also single pipe exhaust. So all pulses are merged in perfect timing.

    N54 335i has twin turbo but equal length downpipes resulting in same effect.

    No comparison with S55 setup.

    I had an E90 330i too, naturally aspirated so no contest..
     
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  8. 17 Jan 2020 at 7:48 PM #68
    Doughboy

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    Agree. Just putting big pipes on it won't fix it.

    S55 just sounds like two inline 3's fighting each other. At some rpms it works but at most it doesn't.

    No amount of fancy titanium silencer tech will fix that.

    Balance the lengths then merge.
     
  9. 17 Jan 2020 at 7:54 PM #69
    ZeroFX

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    Ive read this before somewhere else. Its the harmonics of the gases being out of sync. Not much the exhaust can do about that.
     
  10. 17 Jan 2020 at 8:10 PM #70
    Doughboy

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    It's not harmonics which is about resonance and vibration, It's more about the exhaust pulse mix timing.

    Pulses from bank 123 need to interleave with 456 at 120degrees crank rotation intervals. (I6 firing interval is 120deg).

    If 123 pipe is a foot longer than 456 at the merge point all the timing is f##ked. This can sound different of course depending on the difference and rpm. But if it's equal length then the timing won't change at any rpm.

    BTW firing order is same on all BMW I6, RB, 2JZ etc. .=153624.
     
  11. 17 Jan 2020 at 10:48 PM #71
    DeadEye

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    Are you the creator of this “new” exhaust?

    if so, post a video of it please.
     
  12. 18 Jan 2020 at 8:25 AM #72
    Doughboy

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    No not at all, but I've been involved in discussions about it with the U.S. guys for a while and taken a real interest in it from a technical perspective. Also back-read numerous threads going back a year or so. Lots of different theories and trial setups kind of evolved into the recent thread posted at the start of this thread.

    I first contacted a local exhaust place to discuss this in October last year, but have been to busy with work etc to get organised. But since then with ntg44's work its grown legs a bit.

    But i will be creating my own M2C version next month hopefully. Got a few things to try and see. Should be fun..

    There are also guys pursuing varied unequal length systems to create what they feel is a good sound.

    For me as an engineer and car nut the equal length is the technically best solution for creating a clean I6 sound where you can hear each firing pulse.

    With unequal length you often "hear" only a louder 3 cylinder engine because pulses overlap at the merge depending on rpm so the sound we hear is only 3 pulses per 2 crank rotations instead of 6 pulses. Ie it sounds like half the revs and out of tune and louder as the pulses overlap and therefore increase the sound level, but this all changes with rpm to further confuse the issue.

    Exhaust pulse timing is an important part of naturally aspirated exhaust design for performance reasons. But with turbo engines it has no performance benefit post-turbo so it gets forgotten about i suppose.
     
    Last edited: Jan 18, 2020
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  13. 18 Jan 2020 at 11:03 AM #73
    DeadEye

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    I accept all that but at the end of the day I'm yet to see any proof that this exhaust sounds any different than any other which is why I'm asking for a vid...
     
  14. 18 Jan 2020 at 11:13 AM #74
    Railgun

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    There are a few in the thread on bimmerpost.

    I think the effort of a proper equal length is only part of it though. I properly sized/designed muffler/resonator is the other. I just don't care enough to do it myself.
     
  15. 18 Jan 2020 at 11:25 AM #75
    Chrisyboi

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    Surely it’s not hard to have someone make up an equal length downpipev? It’s hardly a complex bit of fabrication. Company’s like Walton motorsport, APW or autoworx will easily do something like that. My car has just had a full custom turbo back system from Autoworx.
     
  16. 18 Jan 2020 at 11:52 AM #76
    Unit

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    Totally agree mate. I *get* the initial hate for the launch cars after the V8 of the E92 as they did sound like farty tractors. I didn't like it tbh but I got used to mine. However the Comp Pack really fixed it and I think they sound great. I have an 18 plate pre-OPF car and haven't felt any need to add an exhaust or mod it.
     
  17. 18 Jan 2020 at 12:08 PM #77
    Doughboy

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    When I've had the work done then I'll get some audio up.

    Yep, the equal length fixes the pulse timing issue, but then the mufflers etc will set the tone. No amount of mufflers can sort the pulse timing out though.

    Agree, that would be a good fix. The US guys looked at that but space is the main issue. There's not really room to fit in a foot of extra downpipe onto the rear 456 bank post turbo right at the bulkhead. You can barely squeeze a hand in there let alone over a foot of 3" tubing and still have clearances for movement.

    But if someone can do it, fair play to that.

    You can see how short the rear DP is and how little space between turbo flange and DP end flange there is:

    [​IMG]
    [​IMG]
     
  18. 18 Jan 2020 at 12:44 PM #78
    harrypevo

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    The exhaust pulses are all messed up by the bloody great windmil sat in the exhaust!

    A lot of turbocharged cars over the years have been ruined by fancy equal length exhausts. Sure it's good for power, but it can also remove a lot of the character the uneven pulses give to the exhaust sound.

    I wouldn't be getting my hopes up until I'd heard one in the flesh.
     
  19. 18 Jan 2020 at 4:12 PM #79
    Doughboy

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    The pulse timing is not altered by the turbine. Sure the pulse pressure wave shape is blunted but not the timing of it relative to engine speed.

    We're talking about after the turbo where it makes no performance change at all.

    The best post-turbo exhaust for performance is no exhaust at all. The next best thing being a straight pipe out the bonnet or something.

    ...not very practical though :)
     
  20. 19 Jan 2020 at 8:10 PM #80
    Mr Hankey

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    :beer:
     

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