Calling engineer types - exhaust technology

Discussion in 'General' started by HPPT, Apr 14, 2022.

  1. cBJr

    cBJr Well-Known Member

    Yeah, no argument there. I can't see it making a significant difference. But given the assumption all other things equal, that's the biggest effect I would expect.
    G 97 likes this.
  2. pfhenry

    pfhenry Well-Known Member

    That is fucking thin!!!
    Ducati89 likes this.
  3. pickled egg

    pickled egg Works with puppies, too

    Pfft. Like we’ll take your word for it without seeing your report card. :Poke:
    Ducati89, Trainwreck and 27 like this.
  4. nlzmo400r

    nlzmo400r Well-Known Member

    If geometry is identical different material won't make any chance, especially on something like a small gas engine. Metal surface conditions could play a factor here or there, but again, if we're looking at a 150hp engine it'll be negligible and I'd argue almost immeasurable.

    For a combustion engine the biggest factor in exhaust design (beyond the cylinder head) will be the primary diameter and length and collector length and shape. Most other things don't matter in the grand scheme of things.
  5. Steeltoe

    Steeltoe What's my move?

    That's what she said.
  6. pfhenry

    pfhenry Well-Known Member

    lol I had to look it up.. thats like welding 30 gauge.
  7. Trainwreck

    Trainwreck I could give a heck

    Inconel is also a very popular material when 3D printing exhausts, or any other extremely high heat fluid transfer system.
  8. Black89

    Black89 Well-Known Member

    I would look into thermodynamic simulations. I’m an EE but our thermal team does simulations and different materials have different emissivity. This could make a difference in heat transfer.
  9. nlzmo400r

    nlzmo400r Well-Known Member

    It'll certainly make a difference in heat transfer, but at this scale that heat transfer will make almost zero difference in exhaust velocity. And if there's no difference in velocity there won't be any change in how effective the air pump behind it is.
    G 97 and HPPT like this.
  10. tzrider

    tzrider CZrider

    The wave action 'air pump' isn't based on exhaust velocity but rather on the speed of sound wave doing the actual 'pumping' and the length of pipes (primary & secondary) an exhaust will have.
    Speed of sound varies with heat so, for example, adding pipe insulation is a sort of a cheat to shorten pipe lengths.
    The main advantage of Ti is its lightness and capability to withstand extreme heat.
    The heat transfer is an interesting possibility for the power difference, meaning that a steel pipe to the correct lengths would pretty much emulate the same power curve.
    Speed of sound varies with pressure (or back pressure in this case) so finding cause/effect can become very tentacular. :D
    Michael Hausknecht, 27 and CBRRRRR999 like this.
  11. Britt

    Britt Well-Known Member

    It is also very fun to weld...625 and 718, check out any of the jet engine stuff..(yes, I welded 98% of their prototype little engine and the Aft engine combustion chamber, some of it is sheetmetal not printed, on the new J85 setup.)

    Many factors in exhaust flow, Laminar Flow, Deformed Flow and Boundary Layers need consideration in design, Material selection is mainly decided by Costs, Weight, and Operational Heat parameters.
    Last edited: Apr 14, 2022
    vfrket, Phl218, Steeltoe and 6 others like this.
  12. Knarf Legna

    Knarf Legna I am not Gary Hoover

    The thermal transfer of titanium is about a 60% of stainless, so it heats faster. Hotter gasses flow better. All things equal it won't make much of a difference in HP. Unless a turbo is involved.
    Trainwreck likes this.
  13. pawpawrc

    pawpawrc Well-Known Member

    Ok that’s pretty badass. I had never even heard of these guys.
  14. pfhenry

    pfhenry Well-Known Member

    i remember an add from a motorcycle
    i cant imagine welding that thin on my 83 miller dial arc... u using purple 1/16th tungsten?
  15. Montoya

    Montoya Well-Known Member

    No idea why, but remember reading a technical article years ago with the head engineer of a major motorcycle exhaust manufacturer… stating he didn’t know why to exhausts sometimes provided more hp either. Always struck me as brutal honesty. Not my discipline or specialty, there’s a lot of plausible explanations… but am sure it’s not a simple answer.
  16. backho

    backho Well-Known Member

    Inconel 625 also is highly corrosion resistant.
    Trainwreck likes this.
  17. Trainwreck

    Trainwreck I could give a heck

    Yes, that is very true. However, in motorsports I am not certain that corrosion resistance is much of an advantage. Most cars at the level where exotic alloys are being used get torn down pretty far between rounds.
  18. nlzmo400r

    nlzmo400r Well-Known Member

    much better said. I know with my limited knowledge of designing exhaust systems on cars and bikes, the Ti/exotic material has always made zero change in power, but length and collector placement etc have made huge changes. I don't know why but I've never taken into account designing the lengths for the specific material being used.

    Everyone complained about the 'torqueless 1199 Panigale' when those came out - my buddy designed an exhaust to try to help that situation about 10 years ago and it worked VERY well. And this was long before any of the current long pipe/undertail type panigale units we see today. When this design was made, everything was still 'KTM style' two canisters under the sump type of routing.
  19. R Acree

    R Acree Banned

    Fack!!!!!have we slipped into a time warp?
    G 97 likes this.
  20. iagsxr

    iagsxr Well-Known Member

    I understand them to be a ride quality thing because the unibody chassis is so flexible with no roof to tie it together.

    Thermal coat the stainless exhaust and go back to the dyno. One way or the other it will be a tell if it's a heat transfer/thermal dynamics thing.
    27 likes this.

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