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Thread: Daytona Drone

  1. #1
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    Daytona Drone

    I know this topic has been beaten to death on here, but I can not find an answer to my question. I have a 1992 Daytona IROC R/T. It has a 3" exhaust, down pipe back and soon to have a 3" down pipe too. I have a "Dynomax" Race Bullet Muffler in the middle of the car and a Magnaflow Oval muffler in the rear. There is no CAT. I added the rear muffler a year ago to quiet it down but the car still drones bad at highway speeds. I am understanding that this could be due to my exhaust exiting on the driver side slant cut at the same height as the bumper. So I am willing to extend it past the bumper, I am just looking to see what other people have done for a tail pipe and if this gets rid of the drone. Here is a pic of the back of my car. Thanks in advance.

    Thinking this down pipe may be part of the problem too.




    Here is a pic of the back of my car. Thanks in advance.
    Last edited by DoubleD; 01-22-2013 at 12:21 PM.

  2. #2
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    Re: Daytona Drone

    Exhaust noise is very subjective. With that said, IMO if you are going to keep the 3" exhaust, you are going to need to put on a chambered muffler. The hole is just too large to really be quiet. Every 3" straight thru muffler I have heard on a TM will get maybe not droney, but loud anyways at certain RPM's. I had two 3" straight thru mufflers, a oval GN ATR billet muffler and 3" round stainless Ultraflow on a masi 16V omni trying to quiet the car down. It was acceptable in the end, but just barely. WOT was still louder than I wanted.
    I have no cat and one chambered muffler on my 3" exhaust on my Shadow. Yes I'm losing some HP with it, but it's not loud or droney at all. For me, lesson learned.
    Todd

  3. #3
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    Re: Daytona Drone

    Have you tried the weights they put on luxury cars exhaust? If you look under the Lincolns you'll see them attached to the exhaust pipe. that's what they are for to eliminate noise/resonance. It's cheap and doesn't restrict flow may be worth a shot to see if it helps. I've gotten a couple out of the junkyard to try and kill the horrendous drone I have on my wagon but have not had time to try them out.

  4. #4
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    Re: Daytona Drone

    Definitely get it exiting clear of the bumper and bodywork. If you want to test, find an old rad hose the same diameter and cut an elbow and/or a 6" straight off it, and you can aim it down, off to the side, etc etc, to see which works best...
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    Re: Daytona Drone

    If its at the stock location, that's pretty good. As for drone, I've chased it for years. Make sure the exhaust doesn't touch any part of the car, use OE rubber hangers, and put a cat in place of the front muffler otherwise run some form of an OE type muffler or chambered muffler IE import Flowmaster as they have more drone control. You'll lose a bit of power but if you want quiet. I finally shut mine almost up and now have a 3.5" cutout if I want full power. Should have done that years ago,
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  6. #6
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    Re: Daytona Drone

    Does anyone have pictures of a Daytona with 3" exhaust? I want to see how the back will look.

  7. #7
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    Re: Daytona Drone

    I have been looking at pictures of Daytona's on Pbase and Google Images and I have yet to find one Daytona with 3" exhaust exiting below the bumper. All of these cars seem to be exiting behind the bumper, I don't get how they don't drone. Any help would be greatly appreciated with pictures too.
    Thanks

  8. #8
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    Re: Daytona Drone

    Isn't the drone a resonance? A certain RPM generates a certain frequency that resonates and that is where the darn noise comes from. There is such a device which can read the frequency of such sounds, and I think one of the objects is to not get the exhaust quieter, but to generate sound waves that are out of phase of each other so that they cancel each other. How to do that, I do not know, but if we can determine the wavelength and create exhaust exits that do this, it may accomplish the goal somehow.

    or maybe I am just thinking of it all the wrong way.

  9. #9
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    Re: Daytona Drone

    Drone is resonance, yes. However, if the tip exits behind the bumper, it traps the sound and amplifies it at certain frequencies making it worse. The 2nd and 3rd gen G-bodies with ground effects are kind of difficult to get the exhaust tip past the bumper without cutting the cover. I don't suggest that simply because it ruins the cover. However, adding a turn-down that aims the exhaust down and away from the car will help not only the sound inside the car, but outside as well.

    Another thing to try, some sort of dynamat over top of where the rear muffler is. The whole rear hatch of G-bodies is VERY good at amplifying low frequencies (part of the reason they are good for bass on big stereos...about 22Hz IIRC). It doesn't restrict flow, it only adds a little weight, and it could possibly solve the issue to the point of being acceptable.

    As Simon stated, take off the middle muffler and put a hi-flo catalytic converter in its place. The ONLY reason I have a cat on my car is to reduce the decibel level and the drone. It did exactly what I wanted it to! Hey, and I can claim I'm making a good bit of power WITH a cat in place...that blows some people's minds. My exhaust tip does extend past my bumper cover by maybe about 1/4" or so, but my bumper cover is a stock Shelby Z one, so it doesn't have any sort of rear ground effect on it at all.

  10. #10
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    Here is how my current exhaust exits the back.

  11. #11
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    Two more up close pics.


    Any input is appreciated.

  12. #12
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    Re: Daytona Drone

    I would get one of those band style muffler clamps and a 45 bend. Extend it out and see what it does. Try pointing other directions if straight back doesn't do well.

    If you don't like chambers, try a louvered core muffler. Its a good compromise between a straight thru and a chamber.
    MinivanRider

  13. #13
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    Re: Daytona Drone

    I agree...extend the tip out farther. And as stated above, try different angles, too.

    Have you installed a cat in place of the center muffler, yet?

  14. #14
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: Daytona Drone

    I would also try extending the tip, and possibly adding some Dynamat type product. There are other quality alternatives without the Dynamat name. Just try to stick with butyl products vs asphalt.

    I've also heard of people trying laying heavy moving blankets over the floor of their trucks or cargo areas with varying degrees of success.
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  15. #15
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    Re: Daytona Drone

    Ultimately, I think the G-bodies are acoustical nightmares. I drove a dynamat-filled IROC R/T a few hundred miles to Ohio years ago, and it was still loud. Base model G-bodies of this era have no sound insulation in the trunk, and the ES models and better do, but it doesn't seem to make much difference either way.

    Feel free to give experience otherwise, but at ~2800 RPM on the highway, the 4 cylinders are at their loudest. The V-6 cars are at their quietest at 2800 RPM and are at their loudest at about 2100 RPM. I see sort of a pattern here, but would need to do some calculations to determine the frequency and wavelength of the exhaust of a 4 cylinder engine at its 2800 RPM and that of a V-6 at 2100 RPM. Create dual-exhaust tips that are spaced apart so that the sound waves are 180 degrees apart from each other, and they should, theoretically, cancel themselves. Also, the length of both exhaust tubes would have to be a "multiple" of each other to make this happen.

    Or maybe I am over-analyzing the situation or maybe the wavelengths will prove to be impractical to work with--if the wavelength proves to be 7-feet or so.

  16. #16
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    Re: Daytona Drone

    Interesting. I just did some quick calculations, and I'd like others' opinions on what I discovered.

    Assuming that the number of power strokes that an engine makes per engine revolution directly corresponds to exhaust frequency...

    a 4 cylinder engine performs two power strokes per engine revolution. Simply put, you take the RPM and multiply it by 2 in order to get the number of power strokes per engine revolution. 3,000 RPM * 2 = 6,000 power strokes per minute. This is right about where I find the 4 cylinder engines to be the loudest.

    A 6 cylinder engine performs three power strokes per engine revolution. Simply put, you take the RPM and multiply it by 3 to get the number of power strokes per engine revolution. 2,000 RPM * 3 = 6,000 power strokes per minute. Right about where the 6 cylinder cars are at their loudest on the highway.

    Coincidence? I'm not sure yet. I am going to punch up some more numbers to see what else I can find. I am unsure as to how the doppler effect is going to come into play here. In theory, that would require factoring in the velocity of the exhaust and speed of the vehicle. Vehicle speed minus rear-ward exhaust velocity. I have no idea what the exhaust velocity is. Bigger exhaust should result in slower exhaust though. hmmm

  17. #17
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    Re: Daytona Drone

    Okay, I didn't plan on coming to any conclusion that is actually starting to make sense, but it is starting to seem a bit less coincidental.

    6,000 power strokes per minute is 100 power strokes per second. That is 100 hz. Thinking that was low, I pulled up a youtube clip of a 100hz sine wave to compare. Darn, that sounded strikingly similar, though I haven't driven my loud 4 cyl G-body extensively for over a year now.

    So, at sea level, at 72 degrees fahrenheit, the speed of sound is 763 mph. Subtract 60 mph since that is the speed the car is moving at a V-6's loudest, and you get about 700 mph Doppler-corrected sound speed. The wavelength of 100 hertz sound wave moving 700 mph? 10.3 feet! That is pretty darn close to the dimensions of the combined steel passenger and luggage compartment of a G-body. Conditions are sufficient for exhaust tone resonance.

    As a side note, when driving my Geo Metro which lost its muffler several months ago, I could move my head closer to the windshield, and the exhaust drone became substantially more bearable.

    So, I thought more about my idea of dual exhaust tips to cancel the noise and have not yet factored in the wavelength in hot exhaust so I am going to assume the same 10.3 foot long sound wave. With a sound wave 10.3 feet long, it would only take a 5.15' space between the tips to produce sound waves that are 180 degrees out of phase from each other, which is do-able. However, the length of the exhaust tubes would have to be considered. Unless you can find a way to make the exhaust tubes exiting the left and right side of the car equal length, the sound waves will not cancel each other. The sound will have to travel an extra 5.15' to the other side of the car by just splicing in a "Y" behind the rear "axle", so the sound waves are going to match up when they are emitted, and thus accomplish nothing.

    Any brainiacs out there who can de-bunk this?

    These conclusions are strengthening my ideas of a faux-dual exhaust setup with an electric cut-out, so I can divert the exhaust to a muffler on the passenger side when I want to, and then have balls-out exhaust out the drivers side, or possibly a little bit of both.

    Lastly, has anyone considered an audio noise cancelling setup? Basically, all that would be necessary is some kind of amplifier, speakers, and microphone in the rear of the car that inverts the sine wave and emits new sound to cancel it. Fighting sound with sound in other words.

  18. #18
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    Re: Daytona Drone

    Seems to make perfect sense to me! Good job!

    Now, keeping in mind I haven't driven my V6 Daytona since the early 2000's, I seem to remember my V6 Daytona being its loudest at right around 60mph, which I think was around the 2000 rpm area.

    Now, something I learned and fully agree with is from a site somebody posted up here (possibly in this thread) about different sound reducing materials.

    Dynamat (and similar products) are made to reduce panel rattling and resonance. To reduce actual SOUND decibel level, you need some sort of closed cell soft foam to absorb and insulate the inside of the car. Let me see if I can find that link and I'll repost it.

    ---------- Post added at 01:08 PM ---------- Previous post was at 01:03 PM ----------

    Here's the link to the site that I learned the information from and it all makes perfect sense.

    http://www.sounddeadenershowdown.com/

    HTH

  19. #19
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    Re: Daytona Drone

    The principle that article is working on is the fact that sound is emitted from a source, which vibrates whatever is in its way, and then vibrates the air on the opposite side which reaches a person's ears. If something is in the way of the vibrations (such as a steel panel) and it resists the vibration, the noise is inhibited and won't pass through it very well.

    With this in mind, a vibrating panel needs the sound deadening stuff to be firmly attached. With the factory original sound mat in the trunk, it isn't going to help stop those low frequency/long wavelength vibrations much. The sound is going to hit the steel, and the steel is going to vibrate around and "slip by" the sound insulation. Now, if that sound mat is firmly attached, the steel cannot vibrate without the mat vibrating as well. Since the mat doesn't like to vibrate, the sound is stopped much quicker. The sound mat can probably be loose if the wavelength is short enough.

    Hmmmmm. In theory, that dynamat stuff would be quite efficient by just strategically placing squares of it every here and there, but it should still be effective when covering something in its entirety. Oh well... its getting a bit late to think.

    If I ever get blessed with boredom, I think it would be cool to test my theory of the equal length exhaust pipes and placing their tips 5.1 feet apart from each other. The math works out to a point, but since sound undoubtedly travels a different speed through steel and the sound will undoubtedly hit the steel before the waves meet each other to cancel themselves, the distance the exhaust tips will need to be placed will have to change because the wavelength has changed.

  20. #20
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: Daytona Drone

    Interesting point to add to your theory.

    Srt4 owners with unequal length dual outlet exhausts have reported more drone with unequal length dual exhausts than with equal length pipes, or single exhausts.
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