Suggestions for muscle car sound muffler without drone

Mopar Exhaust Systems

  1. Robj

    Robj FABO Gold Member FABO Gold Member

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  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    These resonators are VERY interesting
     
  3. buck351

    buck351 Well-Known Member

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    An amusing point is here you may have thought what am I going to use this stuff for from Physics class when they were going over wave physics.

    I used the phone app I listed in the thread. On a my S3 android phone you can do a screen capture. I also took the file off the phone and put it on the computer that was connected to my 55 TV so I could more accurately measure the frequency on the graph.

    Yes the spike was where you want to tune it to. Actually from what I read it seems 125 to 130 something seems to be a common frequency for drone.

    Yes you include the length of the 90 and from what I read you don't have to worry about 90 effecting how it works. I assume a smooth larger radius 90 is better than a sharper bend.

    There is an equation for calculating the length but I found the site I listed an interesting alternative. I just plugged in some close length dimensions and it calculated the frequency the pipe was tuned to and the DB level Plus the harmonics. Larger diameter creates a larger DB of attenuation. If you try the same length dimensions on the site with different diameters you will see a difference in the DB level. I found the DB created by the 1.5" was more than the DB of the drone measured in the car with the 2" tail pipes. 1.5" diameter pipe was easier to fit too. I had thought about fitting them next to the mufflers but the location I came up with in the photo I like better. Also welding them on the pipe would make it harder to take things apart. So would a stub connection so I choose to make a saddle connection and use some muffler sealer. If you create a cap with some length for the end of the resonator, instead of welding it, and clamp it you can have some length adjustment to tune it. I would have tried it if I was a better pipe welder.

    I'll have to check on the length I used but I was running calculations in the 25" to 28" range. Maybe in the thread. I'll check.
     
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    • Robj

      Robj FABO Gold Member FABO Gold Member

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      I used the calculator last night and came up with 27.2' so that's in the range you have. I like the idea of tuning it with a loose cap. Thanks for all the ideas and information.

      I drove 90 miles today and was wishing it was already done...
       
    • buck351

      buck351 Well-Known Member

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      If you go here
      http://www.diracdelta.co.uk/science/source/q/u/quarter%20wave%20tube/source.html#.U0sfFVpOVaQ and use a 27" long 1.5" dia pipe connected to a 2" dia pipe you will get 125hz. You have to convert to meters for dimensions. You will get the following. Vertical axis is DB. Looks like I cut it off when I did the capture.
       

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    • buck351

      buck351 Well-Known Member

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      You are welcome. Let me know how it works out.

      I asked a muffler shop how much he wanted to install this once. This was a place that did custom work. Regular Midas won't do it. He wanted $200 and you needed to give him all the dimensions. I assume he would have welded it in place. He did one for a Dentist on his BMW and it didn't work. Talking with him I found out he just crimp down the end of the resonator and welded it. That's why it didn't work. The sound waves couldn't bounce off the end with it crimped. Needs a flat end.
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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      I've got tons of PVC and ABS around. Easy to work with, I think I'll mock it up with that and then take it to the muffler shop and have them match it up.
       
    • buck351

      buck351 Well-Known Member

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    • Robj

      Robj FABO Gold Member FABO Gold Member

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      Was going to work on it today but the new curbing around the driveway called me instead.
       
    • Hyper-Performance

      Hyper-Performance Late Apexer

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      Recently I was helping a friend work on his set-up (non-Mopar) with a terrible drone. He tried different mufflers without much help. We added an H-Pipe (more to help with the low end torque than the drone) and it did affect the drone slightly. We tried something a bit off the wall. He had two different length Flowmaster 50's, for grins and giggles we threw those on, looks a bit weird but the drone is all but gone!
       
    • buck351

      buck351 Well-Known Member

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      Interesting. I'm assuming it had something to do with changing the frequency a little and level between the two pipes so they didn't resonate. Wonder if this is a repeatable cause and effect. If it is you could just always do it when you change mufflers as a proactive approach for possible drone. Two different length mufflers of the same brand. Be a major experiment to prove the results are repeatable. Especially since drone doesn't always occur in every setup.

      How's it sound?
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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      I've got my pipes ground to fit but every time I get a day off everything changes. Off tomorrow and was planning to mount them and my daughter just told me she needs brakes and an oil change. I should say she asked me if I could work on her car as only a daughter can. Working on the Honda tomorrow instead....
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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      I am sold on this technique. I finally got a free morning with my bro in law and we put the pipes on. The drone is gone, period. I honestly can't believe it. I'll post photos later today. There is still a beautiful muscle car rumble from the exhaust out back but no drone. I drove up my test hill which I have to always drive on the eay home and we can talk, listen to the stereo. You hear the pure exhaust rumble and that's it. My ears have been saved.
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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      Here are the two graphs overlapped in Photoshop. The old graph is ghosted behind the new one. You can see a rise in the 2-10k range but I don't hear anything all that different in the upper range. It is an even tone now which is very clear in the graph. This was recorded on the hill that always bothers my ears coming home from work by our house.

      View attachment pipe compare.jpg
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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    • clinteg

      clinteg Well-Known Member

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      This is sort of strange but I'm running 3" with X pipe and UltraFlo's dumped at the axle. I haven't noticed any drone thus far with them. I expected some but nothing yet. Possibly because they are still new? I do have some Fat Mat on the floor so that may be helping. The floor isn't 100% covered with the deadener. I installed it in patches.
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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      It seems to really depend upon your set-up. Some cars get it and some don't. Sometimes different mufflers or adding an X pipe eliminate it and sometimes they don't. After seeing this thread I searched more on the internet and found this is a sure fire cure for the drone. There's a ton of information out there from truck sites, to Hondas to Mustangs and exotic sports car sites.
       
    • 69_340_GTS

      69_340_GTS Well-Known Member

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      I had a 2001 Mustang GT. They came from the factory with an h-pipe, and the two mufflers were different lengths. I recall questioning this and I was told that Ford did it to reduce drone complaints from customers. I guess it works on Mopars too!
       
    • MoparDaddy

      MoparDaddy Damn Right I Carry!

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      Glad to see the results!
       
    • buck351

      buck351 Well-Known Member

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      Thanks for the update. Glad to here it worked out for you. Nice overlay
       
    • Robj

      Robj FABO Gold Member FABO Gold Member

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      Drove a ton today and it's so pleasant now. We've got a long slight uphill 45 mph blvd in town that I used to stay in 2nd gear for just to make it more bearable. Quiet as could be today in 3rd. Thanks for all the information buck.

      I grew up in Palatine- not too far from you. I took a lot of heat from all the Giants fans at work today wearing my Cubs hat after tarpgate at Wrigley.
       
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      • buck351

        buck351 Well-Known Member

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        Thats great. I have a sister inlaw who lives in Palatine. Small world.

        I tell people for me loud exhausts are only fun for about 5 minutes. Longer drives need more tame levels and no drone. It's also nice to be able to have a conversation or listen to tunes too. :)
         
      • iw378

        iw378 Well-Known Member

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        I got the app just to see where my drone is at. I know it's really bad from about 850 rpm to about 1200 rpm.
        [ame="http://s1277.photobucket.com/user/lukeb70/media/Mobile%20Uploads/photo_zpsea8635ac.png.html"]photo_zpsea8635ac.png Photo by lukeb70 | Photobucket[/ame]
        I assume the big spike at just over 50 is the drone ?
         
      • Robj

        Robj FABO Gold Member FABO Gold Member

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        Wow, that's really low. Looks like about 55Hz. Must shake your fillings in your teeth! Sure that's not your sub with the opening bass line from Cream's Badge playing??? :rock:
         
      • buck351

        buck351 Well-Known Member

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        That is low. Lower than the common frequency for a v-8. Interesting. Is it vibrating any of the car like the rear view mirror? :)
         
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