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Thread: Branch resonators - ways of reducing exhaust drone

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    Default Branch resonators - ways of reducing exhaust drone

    I'm looking for information on the use of branch resonators in order to reduce drone.

    Has anyone used branch resonators? Any information? Links?

    What I'm intersted in is where exactly to put them and how to determine the size (length/diameter).

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    Default Re: Branch resonators - ways of reducing exhaust drone

    found this, seems like an interesting concept: http://forums.corral.net/forums/show...hreadid=496793

    seems like they just put them wherever it fits on the car. to get it exactly right is going to take a bunch of math, but you could always put a T into your exhuast at a convenient place, then use exhaust clamps to test various sizes/lengths of pipe until you find one that works the best.

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    Default Re: Branch resonators - ways of reducing exhaust drone

    Sounds like it would jack with exhaust flow...
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    Default Re: Branch resonators - ways of reducing exhaust drone

    I have read that link before I posted but I can't figure out if it matters where the resonator is welded to the exhaust. Also when I try to calculate the length of piping needed it turns out to something like 2 meters due to the fact that our inline six cylinder engine fires like a 3 cylinder engine.

    I don't see why it would mess with exhaust flow - no exhaust is flowing in the resonator - only sound waves.

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    Default Re: Branch resonators - ways of reducing exhaust drone

    On my old 2jz car, I had a regular summit glass pack resonator with an apexi N1 canister and there was nearly no drone. The car was fairly quiet at idle/cruising (couldn't hear it inside with windows up a/c on and radio on low volume at 70 mph).

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    Default Re: Branch resonators - ways of reducing exhaust drone

    Our BMW 540i has a resonator that has a branch running off of it.

    *Not my pic, but you get the idea*


    To make something like that in a Supra, you'd just need to make the branch in front of the rear diff, and have it come around the diff on the other side of the rear subframe.

  7. #7

    Default Re: Branch resonators - ways of reducing exhaust drone

    HKS puts them right before the mufflers.

    Sometimes just the placement of the muffler in the system will effect drone.
    On an old Corona I owned years ago (first Toyota),
    I had installed a full 2.5" systems with a 'turbo' muffler.
    It was terrible at 60mph!
    My teeth would vibrate.
    Below 50, and above 65, there was no drone.

    I moved the muffler from behind the rear axle, to the original location
    (about a foot ahead of the rear axle)
    and the drone went away.

    So it all depends on the system, and how that particular system sets up resonance.
    Last edited by gofastgeorge; July 13th, 2009 at 09:03 AM.

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    Default Re: Branch resonators - ways of reducing exhaust drone

    Quote Originally Posted by gofastgeorge View Post
    HKS puts them right before the mufflers.
    Which car is that exhaust for?

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    Default Re: Branch resonators - ways of reducing exhaust drone

    Ok, I'm trying to figure out the length of the pipe to use for a branch resonator.

    I use this calculator to calculate the wave length:

    http://www.autolounge.net/calculator...resonance.html

    I assume I need to input the number of cylinders. The 7mgte engine fires two cylinders at the time, so I guess our 6 cylinder engine transforms to a 3 cylinder engine, right?

    If I get drone at 2000 rpm the standing wave length is: 11 feet.

    So I read this:



    http://www.enoisecontrol.com/related...rrier_wall.pdf

    at page 44 there is a formula for the length of the branch resonator. It says lambda/4 where I assume that lambda is supposed to be the wave length of the standing wave which is what causes the drone.

    So 11 feet / 4 = 2.75 feet = 82.5 cm

    The side branch resonator should be the same diameter of the rest of the exhaust (in my case 4 inch).

    So I need 2.75 feet of 4 inch pipe welded to the exhaust right before the last muffler to reduce drone with 20 - 30 db, right?

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    Default Re: Branch resonators - ways of reducing exhaust drone

    Drone is a myth... I have a full 3" turbo back, no cat with a Blitz Nur spec and It its honestly not that loud until under boost or heavy throttle, even then its not all that loud.
    Single turbo 1JZ......Just the basics

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