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A resonant instrument in the Ferrari muffler

Discussion in 'Technical Q&A' started by Geoman54, Jun 27, 2007.

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  1. Geoman54

    Geoman54 Karting

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    Michael McLaughlin
    #1 Geoman54, Jun 27, 2007
    I've poured over the threads on exhaust system design here, the cut-away pics of early and late-design mufflers, and I have a question. As we all know that the sound of our cars is one very alluring quality they possess, is there any source out there that discusses a deliberate internal design methodology to achieve audible bliss?

    I would think that a deliberate series of resonance points in the frequency range of the human ear could be "designed in" while not necessarily costing excess power absorbing flow restrictions.

    From my racing days in driving open-wheel Formula cars I can state that the sweet exhaust note of, say a Lotus Twin-cam at 9200 rpm or a Cosworth BDD at 9500 rpm was intoxicating. Certain engines sound "right" with a open exhaust. However-- street cars are a different animal altogether.

    The un-muffled acoustic "signature" of a Ferrari combustion chamber design and intake air-stream is not available to us (for obvious reasons). A few contributors to this forum seem to have a good handle on making better power. Anyone have a handle on how to make better music?

    I don't believe they are mutually inclusive. For instance -- did you ever hear the exhaust note of a IRL Indy Car with the Aurora/Olds engine? Or --- how about the V-10 Viper?.....

    Regards,

    Geoman54
     
  2. Mike C

    Mike C F1 Veteran
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    #2 Mike C, Jun 27, 2007
    Sure... talk to your Tubi, Stebro, Capriso, X-Ost, or ANSA dealer, and he'll tell you how... buy one of their exhaust systems and bolt it on!!! :p
     
  3. Geoman54

    Geoman54 Karting

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    #3 Geoman54, Jun 28, 2007
    Hey!-- thanks for the "tongue in cheek" response, but my posting was not to seek the "pitch" of an existing manufacturers salesperson on why their system makes better "music" than the other guys, and then open up the wallet and bolt it on. What I was asking was whether anyone on the forum had a lead pointing to the design philosophy on enhancing the acoustic signature of a silencer/muffler.

    There were guys in the different threads that discussed flow characteristics but only subjective reference to sound quality.

    best regards,
    Geoman54
     
  4. jm3

    jm3 F1 Rookie

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    #4 jm3, Jun 28, 2007
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  5. Geoman54

    Geoman54 Karting

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    #5 Geoman54, Jun 28, 2007
    This is exactly the kind of info I was looking for. I appreciate your response. I went through most of the article, printed it and looked at a lot of cut-away views of Commercial product I found under google image search. Now to cut open that 355 fabricated racing muffler I have and start laying out a plan.

    Regards,
    Geoman54
     
  6. k wright

    k wright F1 Rookie

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    #6 k wright, Jun 29, 2007
  7. kens

    kens Formula 3
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    #7 kens, Jul 2, 2007
    Do you have a cut-away pic of the stock 355 muffler?

    Thanks,
    Ken
     
  8. Geoman54

    Geoman54 Karting

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    #8 Geoman54, Jul 2, 2007
    Ken,

    I've only seen the pictures I came across on this site. One was of the internal piping on a stock 360 unit. The other was -- I believe-- of a 308 .

    I would be interested in finding others, but Google image searchs have not revealed anything.

    regards,

    Geoman54
     
  9. kens

    kens Formula 3
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    #9 kens, Jul 3, 2007
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  10. Geoman54

    Geoman54 Karting

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    #10 Geoman54, Jul 3, 2007
    Ken,

    Thanks a lot! I went to the site and the cut-aways gave me a lot of information. I find it fascinating that they choose different internal pipe diameters, some open end---some flared, different back-spacing from baffles and walls, etc. ....all to achieve what I started this thread about....and that was creating a musical instrument while attaining reasonable silencing -- on a high performance engine.

    Now I need to find somebody's design philosophy to get a better idea of how to handle the variables. This is probably the "black art" part of things that is going to prove difficult.

    regards,

    Geoman54
     
  11. f308jack

    f308jack F1 Rookie

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    #11 f308jack, Jul 3, 2007
    What we are talking about here is of course rather subjective, and the science of exhausts is not.
    You guys with longitudinally mounted engines are lucky, as this eliminates much of the problems of tract lengths etc.
    On my 308 GTSi Euro-spec, the PO went a different route: the original exhaust was dissed, and replaced with a fabricated system with equal length for all cylinders. No silencer, and in this country (South Africa) no cats either. Yes, it is loud, but the sound is glorious when you start climbing the rev range. And if I wanted to be inconspicuous, I would have bought a black Golf.

    Ciao,
    Jack.
     
  12. snj5

    snj5 F1 World Champ

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    #12 snj5, Jul 3, 2007
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    There are indeed times I wish the engine was longitudinal - it would make exhaust tuning easier. Actually, as a data point, the small Lambo transverse V-8s also went to a lot of trouble to get tract length for each side about the same. If you look under many Urracos or Jalpas there are pipes running everywhere - and they are well regarded to be the best sounding small V-8.

    Advice I received when I was doing my system mostly all focused on absorptive systems which are engineered a bit different from the resonant chambers like the 355. Anyway, I'm sure you have been through all the threads. We will be building what I hope is my ultimate exhaust here for the car in late July - Good luck with yours!!

    Here are a couple of cut aways on an aftermarket 355 that I looked at:
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  13. kens

    kens Formula 3
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    #13 kens, Jul 3, 2007
    My observation of the 355 drawing the diameter of tubing is likely includes the desired flow rate. The flared tubes all about direction of flow. The back spacing is extremely relevant with sound tuning. Also, note that the only reason for chambers 3 & 5 is spacing. There is no flow in 3 & 5.

    It is likely known, I will pass along for casual readers knowledge anyway. The center inlet on the 355 muffler has its own high flow catalytic converter and is used only with a heavy throttle.

    Ken
     
  14. jm3

    jm3 F1 Rookie

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    #14 jm3, Jul 3, 2007
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    Just in case you ever wanted to know......

    Incidentally, not clear in this picture is that the large center section, that the bypass dumps directly into, and the regular flow is channeled through, has perforated baffles all the way down each side (far away from the flow) to prevent resonance aka echoing.
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  15. Air_Cooled_Nut

    Air_Cooled_Nut Formula Junior

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    #15 Air_Cooled_Nut, Jul 4, 2007
    Exactly. Plus the firing order makes a big difference in sound ;)

    Hahaha, hell yeah!!! :D
     
  16. snj5

    snj5 F1 World Champ

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    #16 snj5, Jul 4, 2007
    I read today that exhaust systems from mild steel have different tonal quality from s/s. Could someone describe that for me, please?

    thanks!
     
  17. Geoman54

    Geoman54 Karting

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    #17 Geoman54, Jul 6, 2007
    It may have to do with the resonant frequency of the carbon vs. stainless steel. I would think that it also has more to do with the design type and wall thickness of material. For instance ---the absorption straight-through as compared to a chambered reflection type.

    Geoman54
     
  18. kens

    kens Formula 3
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    #18 kens, Jul 6, 2007
    In addition, the 355 muffler has exterior clading that must be a factor.

    I have direct experience with a 365 Boxer and 355 muffler. A common trait with these two exhaust systems is that they are both very heavy. Of course, weight is a very negative aspect. So, my guess is that somehow the tone from a large heavy duty muffler is worth the weight penalty. To be fair, wall thickness has been mentioned.

    Then we have the after market mufflers that are smaller and lighter. Do high decibels from these after market systems cover up some negative properties?

    Ken
     

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