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Thread: Daytona Drone

  1. #21
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    Re: Daytona Drone

    Wow, this discussion got very complicated and technical, I wish I could chime in more. I need to dig back out my NVH textbook from college.

  2. #22
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    Re: Daytona Drone

    I'd like to read that book. Definitely post something if you find out. But to be honest, sound waves alone are not a complicated thing to understand. But one thing I don't quite understand is how it correlates with its transmittance through a substance other than air. Sound travels much faster through materials such as steel, and the wavelengths become much longer as a result. If I am thinking right (which has been frequently known to not happen) resonance occurs when a sound wave bounces back and hits another incoming sound wave, in which their amplitudes add to each other and causes the drone a.k.a a "standing wave". For this to happen, the entire sine wave has to complete itself in the distance that it has to work with before it bounces back so it has a chance to resonate. If just the crest of the wave hits a wall and bounces back, the trough of the wave which has not yet bounced off the wall will cancel the reflected crest. However, the crest will be reflected at a lower amplitude, so the trough will over power it and the sound will not be perfectly cancelled, but the amplitude will be reduced. To put it simple, 100 hz sound isn't going to resonate in the chassis of a car because the wavelength is way too long. Significantly higher frequencies such as wind noise and road noises can. Adding sound deadening stuff that sticks to the chassis won't do anything because the chassis cannot resonate with such a low frequency. The exhaust sound is going through the metal chassis and coming in contact with the air inside the vehicle, which just happens to have a wavelength of about 10 feet, which is the size of the passenger compartment. Simply having a notchback setup car would put more barriers in the way of the sound and lower its volume in addition to having a passenger compartment that is less than the wavelength, so the wave isn't going to resonate... at least not at 100 hz.

    Ever notice when the next door neighbor has a party, all you can hear through the walls is the bass? That's because the long, low frequency wavelengths aren't hitting anything that can cause them to bounce back efficiently or get fully absorbed. The higher frequency stuff with the shorter wavelengths are more easily trapped in a wall and such.

    Certain military communication systems utilize gigantic antennas so they can create super long wavelengths which are really tough to jam, because you need a transmitter with an antenna just as big to receive the radio wave and re-create and invert it in order to cancel those radio waves and thus "jam" them. At least I think that is how it works.

    I need to talk to an engineer about it. I know some people who are working for Bose here in the twin cities. I may try them.

  3. #23
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    Re: Daytona Drone

    The resonance comes from the application of sound waves or vibration at a certain frequency to a given volume (of air). It's the exact same concept as a subwoofer box. Even though we can prevent the chassis from reaching its natural frequency (for the most part), the sound waves still make it into the volume and resonate inside the volume.

    So, decreasing the amplitude of the waves is the only real option as we can't alter the frequency (sort of...I'll get to that in a minute). To do that you need sound absorbent material...something that reduces the amplitude. Dynamat does NOT do this very effectively. It's job, and what it was designed for, is to eliminate the panels from vibrating and making it sound like the car is falling apart.

    Ever notice those black bags that Chrysler stuffed in certain voids in the cars behind the interior panels? Those are sound absorbtion devices. Notice how they don't weigh 2 tons, aren't physically attached to the metal, and are squishy? That's because they are an open cell type of material meant to reduce the amplitude of the sound coming from that area. A closed cell material would work even better.

    An active sound suppression system would be pretty neat, and probably not hard to implement, but the thing is, you HAVE to have dedicated speakers in the car for that, or risk loosing sound quality from your music stereo. This type of system on that scale would add weight and complexity to the car, but if you are willing to deal with that, then I'm sure something pretty simple could be made to do exactly that. Just sample the sound in the car with a microphone, run it through a sound wave analyzer, have a logic system that delays the output of the sampled sound by 1/2 of the wavelength, then pump the output to an amp and some speakers. Done. Now,what other kind of problems might this create....who knows? It might interfere with your music! That would suck!

  4. #24
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    Re: Daytona Drone

    Back to the topic at hand, I was under my car last night running an amp wire to my trunk. I noticed that when I had my friend install my rear muffler, he had issues getting it mounted, it looks like the exhaust can swing and hit the frame of the car in a couple of spots, there is also no mount at the very rear to support it. I have a feeling all of this movement may be causing the drone, I need to take my car in and have the mounts fixed, I will get this done while I have my V- band welded on for the Jackson-made Holset Down Pipe. It was a mess under there...

  5. #25
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    Re: Daytona Drone

    If there is no mount holding the muffler, then usually what happens is the pipe going over the axle will hit something in that area and rattle. Plus, yes, the exhaust is very much free to swing around. The rear mount for the muffler is pretty darn important!

  6. #26
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    Re: Daytona Drone

    I have the mount that would look to be inline with the rear tires "sorta" (too much side to side movement for me) mounted, but the mount at the very rear is not attached to anything. Going to take the car to a shop and have it done right! Only issue is finding someone to work on my car with no muffler.

  7. #27
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    Re: Daytona Drone

    Just tell them Neon SRT-4's didn't come with mufflers from the factory and your car is the same!

  8. #28
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    Re: Daytona Drone

    I didst mean muffler, I have two of them. I mean Catalytic Converter. I don't have one of them.

  9. #29
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    Re: Daytona Drone

    Ohhhh! Yeah, unless they do work under the table, most shops now won't mess with that stuff.

    If you get a good high flow converter, it WILL help the drone. I can't remember if that was covered in this thread on not, but I figured I'd mention it. Good converters aren't a restriction to high power anymore. Are they more than straight pipe? Yes. So much you'll notice it? Not unless you are looking for that last n'th of power.

  10. #30
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    Re: Daytona Drone

    I band clamped a 90 bend at my exhaust tip pointed towards the driver's side. It seems pretty quiet at 45 degrees to the ground. Its less droney than my other car with the pipe exiting straight back. I'll experiment with swiveling it to some different angles to the ground later.
    MinivanRider

  11. #31
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    Re: Daytona Drone

    I am in the process of swapping turbos and when I went to remove my down pipe, one of the 3 bolts was missing and the other two were not very tight, my down pipe was not very securely attached to my turbo. This could be part of the problem. Getting ready to install the HE 341 and Jackson's down-pipe,then take the car to a shop to have the rest of my exhaust re-attached. The v-band connection should make sure this never happens again.

    I also have gone thru and covered the entire rear floor with A mass loaded material and I am replacing all of the non-existent carpet padding. I covered and padded the spare tire well also. I hope all of this helps, I also added a nice Kicker 10" Sub in a ported box in the spare tire hole. I would like to get the drone managable or make it go away mostly. Time will tell thou.
    Last edited by DoubleD; 05-14-2013 at 02:29 PM.

  12. #32
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    Re: Daytona Drone

    This should really help with the drone up front at least, much cleaner, and much more free flowing.


  13. #33
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    Re: Daytona Drone

    nice.. when you get a chance could you snap a quick pic of the sub box

  14. #34
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    Re: Daytona Drone

    Very good thread. Just make sure none of your exhaust system is touching the body or cross member. if you have no space between downpipe and the firewall, you will definitely have a drone when driving. If you have an after market bobble strut, don't have it pre-loaded, just have the nuts to where they prevent the engine from rocking back under acceleration.

  15. #35
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    Re: Daytona Drone

    Quote Originally Posted by 88C/S View Post
    If you have an after market bobble strut, don't have it pre-loaded, just have the nuts to where they prevent the engine from rocking back under acceleration.
    I agree with this 100% if you have filled, or poly mounts. However, with stock mounts, a little preload (not much!!) will go a long way in helping wheel hop and even smoothing out the shifting.

  16. #36
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    I have a combination of filled and poly mounts. I think I put a lot of preload on the strut before, I will put very minimal on it this time.

  17. #37
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    Re: Daytona Drone

    Took my car to a local shop to a guy that has been in the business for 40 years. He did great work, ended up swapping the Dynomax turbo muffler for a Magnaflow resonator. He welded that into my system and attached that resonator to my new down pipe. He also added an extra exhaust clamp to the rear and really limited the movement, the drone is much less now.



  18. #38
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    Re: Daytona Drone

    You didn't happen to get any pictures of the inside of the resonator did you?

  19. #39
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    Re: Daytona Drone

    I did not but the Google images search function works very well, the part is a Magnaflow resonator PN# 14419.


  20. #40
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    Re: Daytona Drone

    Cool, so they aren't louvered. That's what I wanted to know! Thanks!

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