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  •  » If you have an anoying exhaust drone here is the SCIENCE to remove it

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    10/26/2023 3:18 PM  #1

    Daze
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    From: Kalispell MT
    Registered: 1/24/2013
    Posts: 1,129

    If you have an anoying exhaust drone here is the SCIENCE to remove it

    After making a DIY exhaust for my 62 the old Gal had a terrible exhaust drone but I was able to fix it with a set of DIY wave resinator tubes.



    https://youtu.be/cwWK-xz7jho

    If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     

    10/26/2023 4:38 PM  #2

    Ron68
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    From: Mukilteo, Washington
    Registered: 4/01/2013
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Cool video Day - If I had a droning issue I would look into this, but luckily I don't. You smart guys amaze me. That is something I never would have thought of to fix an issue like that.

    68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
     

    10/26/2023 5:07 PM  #3

    Rudi
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    From: Stuck in the 50's Welland Ca
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Great idea with a lesson on math and acoustics.
    For myself if I had drone it’s way to complicated, I’d just change one muffler.
    Ford did a good job designing my factory pipes with resonators and transverse muffler , they totally drone free.

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    10/27/2023 6:00 AM  #4

    Mach1Driver
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Yep quarter wave cancellation. What I find amazing is that a sound wave and a radio wave both work the same way. Most microwave ovens have a little chamber (of just the right dimensions) on the door where the microwave enters and is reflected back, cancelling out the main wave and preventing leakage around the door of the oven. Its called a quarter wave choke and works on the same principle. Pretty cool huh?

    Last edited by Mach1Driver (10/27/2023 6:13 AM)

     

    10/27/2023 9:36 AM  #5

    Daze
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    From: Kalispell MT
    Registered: 1/24/2013
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Ron68 wrote:

    Cool video Day - If I had a droning issue I would look into this, but luckily I don't. You smart guys amaze me. That is something I never would have thought of to fix an issue like that.

    Not smart just good with google and willing to fail.  I have always been one to try and if it doesn't work try something else.

    ​

    Rudi wrote:

    Great idea with a lesson on math and acoustics.
    For myself if I had drone it’s way to complicated, I’d just change one muffler.
    Ford did a good job designing my factory pipes with resonators and transverse muffler , they totally drone free.

    There are two issues in my case one it was a DIY exhaust and two it is so large. I don't have the benefit of a factor design so issues like this were not accounted for in the design.  As to the size you see this as a common problem on trucks with custom exhaust.  The bigger the exhaust system the lower the frequency.  I think the exhaust on most Mustangs is so much smaller that the frequencies don't line up in most cases.  Mine was so bad I am not even sure two different mufflers would have gotten it done.

    Mach1Driver wrote:

    Yep quarter wave cancellation. What I find amazing is that a sound wave and a radio wave both work the same way. Most microwave ovens have a little chamber (of just the right dimensions) on the door where the microwave enters and is reflected back, cancelling out the main wave and preventing leakage around the door of the oven. It's called a quarter wave choke and works on the same principle. Pretty cool huh?

    I think  it is very cool
     

    If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
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    10/27/2023 10:07 AM  #6

    Rudi
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    From: Stuck in the 50's Welland Ca
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Just out of curiosity what  was the factories system configuration.
    Typically aftermarket and home brew systems don’t have the benefit of the dollars , engineering and research that the car manufacturers do.
    I can’t remember any o/e dual exhaust set up that had drone. The 05 Mustang I owned had big chunks of cast iron hanging from  the suspension and exhaust in various places. I removed them and couldn’t tell the difference.

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    10/27/2023 11:35 AM  #7

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Daze - you arrived at "4 pulses per revolution" for your Galaxie.  How does one measure, or calculate, this value?  (or did i miss this explanation in the video?) 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    10/27/2023 12:29 PM  #8

    Daze
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    From: Kalispell MT
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Rudi wrote:

    Just out of curiosity what was the factories system configuration.

    It was a problem addressed from the factory.  This picture is a 61 Galaxie I parted out but same chassis and exhaust.  If you look at the large round exhaust pieces just behind the back wheel those are resonators.  The mufflers were under the car in front of the axle.  I didn't know any better at the time didn't realize their function.


    BobE wrote:

    Daze - you arrived at "4 pulses per revolution" for your Galaxie.  How does one measure, or calculate, this value?  (or did i miss this explanation in the video?) 

    Sorry I should have addressed that in more detail.  V8 each cylinder fires every other rotation so 4 detonations/pulses  per revolution.
     

    If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
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    10/27/2023 2:01 PM  #9

    Nos681
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    From: Atlantic Mine, Michigan
    Registered: 7/14/2016
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Does this apply to single exhaust systems?
     

     

    10/27/2023 2:12 PM  #10

    Daze
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    From: Kalispell MT
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Nos681 wrote:

    Does this apply to single exhaust systems?
     

    I don't know, however my exhaust has an x pipe so from a harmonic stand point it is sound from both sides exiting both sides very similar to sound from both sides exiting one pipe SOOOOOO my guess would be that it would work with a single exhaust the only difference is you would only need one.
     

    If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
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    10/27/2023 4:25 PM  #11

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

    Daze wrote:

    Rudi wrote:

    Just out of curiosity what was the factories system configuration.

    It was a problem addressed from the factory.  This picture is a 61 Galaxie I parted out but same chassis and exhaust.  If you look at the large round exhaust pieces just behind the back wheel those are resonators.  The mufflers were under the car in front of the axle.  I didn't know any better at the time didn't realize their function.



    BobE wrote:

    Daze - you arrived at "4 pulses per revolution" for your Galaxie.  How does one measure, or calculate, this value?  (or did i miss this explanation in the video?) 

    Sorry I should have addressed that in more detail.  V8 each cylinder fires every other rotation so 4 detonations/pulses  per revolution.
     

    Are you sure about four firing per revolution?  Does distributor rotate at half crank speed?

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    10/27/2023 4:51 PM  #12

    Daze
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    From: Kalispell MT
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    Re: If you have an anoying exhaust drone here is the SCIENCE to remove it

     

    Are you sure about four firing per revolution?  Does distributor rotate at half crank speed?

    I’ve never thought of it in terms of what the distributor is doing, but I can only assume the distributor is moving at half speed? All I know is it takes two full rotations for one combustion cycle. You draw fuel and air in then you compress the fuel and air.  that’s one rotation. Then you ignite fuel and air, causing the piston to go back down into the bore and then you push the exhaust out that’s a second rotation. With eight cylinders and two rotations required per each cylinder fired, you only get four ignition’s in one rotation .

    If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
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