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  • Why round exhaust pipe?

    seriously.
    Doing it all wrong since 1966

  • #2
    A circle has the most area for the circumference. More airflow for less steel.
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    "If it don't go, chrome it!" --Stroker McGurk

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    • #3
      Because square exhaust clamps wouldn't work right!!
      Life is short. Be a do'er and not a shoulda done'er.
      1969 Galaxie 500 https://bangshift.com/forum/forum/ba...69-galaxie-500
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      1983 Mustang GT 545/552/302/Turbo302 http://www.bangshift.com/forum/forum...485-bbr-s-83gt
      1973 F-250 BBF Turbo Truck http://www.bangshift.com/forum/forum...uck-conversion
      1986 Ford Ranger EFI 545/C6 https://bangshift.com/forum/forum/ba...tooth-and-nail

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      • #4
        I just watched a video on that..but my eliptical internet lost it..have to wait for next july for it to come back.

        a tiny squish, lke half inch making an oval, knocked out several cc, and the guy proved it on video with beakers and fluids..and thoroughly explained something simple.

        as heat is an ongoing chemical process..round does something for that as well. not just volume of blasting the crap out.

        like mandrel at the head..it is a big thing to notice.
        Previously boxer3main
        the death rate and fairy tales cannot kill the nature left behind.

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        • #5
          A corollary to Jim's post is that boundary layer losses in laminar airflow are minimized in a round pipe. That said other concerns can out weigh the round pipe theory. This is usually a situation where packaging, sanctioning body rules or aero concerns have a greater impact on the overall exhaust system.

          In my case I used Dr. Gas frame clearance tubes, oval shaped with transitions from round to oval and back in order to squeeze the engine and trans I picked into th car I picked and still maintain some degree of street able ground clearance. Is it ideal, is it a good compromise? IMHO yes. Look at the boom tubes, flat ' mufflers the NASCAR guys use for another example.

          BTW Dr. Gas shut down their retail business last year.
          Last edited by CDMBill; July 28, 2012, 10:10 PM.
          Drag Week 2006 & 2012 - Winner Street Race Big Block Naturally Aspirated - R/U 2007 Broke DW '05 and Drag Weekend '15 Coincidence?

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          • #6
            Boundary losses should be eliminated in a large enough box

            There is a point to my question - I need to lose the pipes from under the IRS on the Corvette, but I'm not looking forward to unflattening side exhaust pipes every time I drive this lowered car into a driveway ramp or speed bump (where it goes under the frame) so - mathmatically speaking, pi *r2 = ~ 5 square inches (on 2 1/2 pipe).... which would be neat if 1 1/4 x 5 side exhaust tips would be no net loss in flow..... unless, of course, there's something I'm missing about airflow of round pipe.
            Last edited by SuperBuickGuy; July 28, 2012, 10:20 PM.
            Doing it all wrong since 1966

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            • #7
              Originally posted by SuperBuickGuy View Post
              Why round exhaust pipe?
              So you/the factory can bend it more easily/cheaply.
              www.BigBlockMopar.com

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              • #8
                If it ain't round then it is an exhaust duct not pipe.
                A Carter Carb Shop, sales and service

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                • #9
                  Originally posted by SuperBuickGuy View Post
                  Boundary losses should be eliminated in a large enough box
                  ......
                  which would be neat if 1 1/4 x 5 side exhaust tips would be no net loss in flow
                  A flat box has more boundary loss than a square box.

                  I'm getting a chuckle out of this discussion, remember I just put some new front springs in my 55, now I can get under the car without jacking it up first
                  My fabulous web page

                  "If it don't go, chrome it!" --Stroker McGurk

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                  • #10
                    Have you ever considered that the exhaust pipe is round because that's the easiest way to make pipe?
                    Act your age, not your shoe size. - Prince

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                    • #11
                      Originally posted by squirrel View Post
                      A flat box has more boundary loss than a square box.

                      I'm getting a chuckle out of this discussion, remember I just put some new front springs in my 55, now I can get under the car without jacking it up first
                      Yet if you climb under your house, you'll note that the main lines are square, and branch to round... when I asked the question, my initial thought was "dumb" but, I've never seen it discussed; nor do I believe know everything - thus I ask.... and it is a funny question

                      Originally posted by studemax View Post
                      Have you ever considered that the exhaust pipe is round because that's the easiest way to make pipe?
                      perhaps, yet with today's manufacturing methods, making square turn is as easy as hydroforming.....
                      Doing it all wrong since 1966

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                      • #12
                        interesting indeed.. I hadn't ever given it that much thought beyond the diameter.

                        Price would be my first response - oval tubing is kinda bucks up. I was looking into it for the turbo downpipe on the F250, and got sticker shocked pretty bad. Bad enough to consider yanking the mill and beating the crap out of, errr, clearincing the firewall with a sledge. I found out people were using a portapower with the engine in place.
                        Flying south, with a flock of bird dogs.

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                        • #13
                          Originally posted by SuperBuickGuy View Post
                          Yet if you climb under your house,
                          around here, houses are all built on concrete slabs.

                          But yeah...making a big square duct is easier to branch off of. This has nothing to do with exhaust tubing.
                          My fabulous web page

                          "If it don't go, chrome it!" --Stroker McGurk

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                          • #14
                            Originally posted by SuperBuickGuy View Post
                            Boundary losses should be eliminated in a large enough box

                            There is a point to my question - I need to lose the pipes from under the IRS on the Corvette, but I'm not looking forward to unflattening side exhaust pipes every time I drive this lowered car into a driveway ramp or speed bump (where it goes under the frame) so - mathmatically speaking, pi *r2 = ~ 5 square inches (on 2 1/2 pipe).... which would be neat if 1 1/4 x 5 side exhaust tips would be no net loss in flow..... unless, of course, there's something I'm missing about airflow of round pipe.
                            There will be some minor loss, but you'd need to run a bunch of Pipemax calculations or other software to figure what is ideal. Better to make it look good and give the ground clearance you want.
                            Drag Week 2006 & 2012 - Winner Street Race Big Block Naturally Aspirated - R/U 2007 Broke DW '05 and Drag Weekend '15 Coincidence?

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                            • #15
                              Originally posted by squirrel View Post
                              around here, houses are all built on concrete slabs.

                              But yeah...making a big square duct is easier to branch off of. This has nothing to do with exhaust tubing.
                              I can speak to HVAC because I'm a licensed journeyman (yeah, I have a few classes under my belt) it's square because turbulance is bad in a house-hold system (noise) that's why you have a squirrel cage (snicker, unintended pun intended ) - it moves air without turbulance, and you get great volume. In exhaust (commercial kitchen ductwork) the pipe is square because it's easier to clean out; but it is more labor intensive then round.... but still, I'm not hearing anything which would say "it's a bad idea to go to square and out." Square is really easy to make in 1 plane radii.
                              Doing it all wrong since 1966

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