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D.I.Y. Sound Insulation (lots of photos)

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  • D.I.Y. Sound Insulation (lots of photos)

    Hi everyone!
    Well, I had mentioned here before that I was going to do a sound insulation project on the Deathegg ('88 L+), and said that if it worked, I would do a write-up on it.
    Well, it works pretty well, so here it is!!

    I was getting quite tired of the high sound level on my car. I know engine noise is a main cause, but in this project i concentrated on road noise first. I plan to insulate the interior from the engine noise soon.
    After reading up on various methods of insulation, I found that there are different frequencies entering the car from different sources, and many different methods of insulation depending on who you talk to, so I took in all this info and made up my own sound insulation package employing different materials.

    Step one was to basically gut the entire interior. pretty much everything came out so all the different materials could go in. The only parts I did not insulate on this project were the doors, since I had already put Dyna-mat in them a few years ago.

    First was Dynamat (or in my case a cheap substitute). I know you don't have to cover everything with this material in order for it to be effective, but since I got it cheap, I DID cover pretty much everything in the car.

    In this pic I don't yet have everything covered, but I did cover everything: floor, inner panels, inner wheel wells, spare tire well, etc. Even did as much of the interior of the hatch as I could.

    Next was taking care of the inner quarter panels areas; the area between the actual fender and the inner panel where the plastic interior pieces attach to. I have read different ways of doing this: expanding foam, rigid insulation, etc. I decided on two materials: spray foam insulation, and actual fiberglass insulation, commonly used for homes.
    The spray foam takes a few practice "beads" to get used to how it adheres and how much it expands. There are two versions of this foam; one is a little harder and expands more than the other. I tried both, and found that it really doesn't matter. They seem to expand in the same way, and adhere the same too. As you can see in the pics, there are many "beads" of foam on the inside of the quarter panels. Again, Everything that i could reach was covered in that area, and put lots of it down near the rocker panel area.


    Then the fiberglas insulation over that. This is 3" thick insulation, so it just holds itself in place against the braces you see. This is just one pic, but again, it also went in the rear near the taillamps, and also into the void under the hatch latch.

    So, that took care of the side structures.

    Now the floor. I went to the local fabric supplier,and found two types of jute backing. One is a black jute, 1/2" thick, and a grey jute with a foil backing, much the same as OEM. It's much more dense than the black type, and more than twice the price, so i only used it on the front half of the floor and parts of the tunnel:

    I used 3M spray adhesive for these materials. Just spray both sides, wait a few secs for it to set, and press into place. Using this stuff, you will NOT have a second chance to get it in the right place, so be sure you have the jute in the right place before you actually set it in place!!
    On the rest of the floor (from the front seat brace ALL THE WAY TO THE REAR OF THE CAR), I used the black 1/2" jute:


    I'll say it again: it's not shown on these two pics, but EVERYTHING from the front seat brace to the hatch latch plate is done with this, including the spare tire well. I did cut out sections to fit the filler neck plate and the plate for the electrical connection for the gas tank, and fit jute pad to these parts individually, so I can still remove them if necessary if I have to, yet still have the insulation on these areas.

    Then, I decided to do the actual interior panels. These took forever, since they are all curvy, and have a combination of different ways of attaching them to the car. These various clips, screw holes and alignment posts have to be cut out individually, or else the panel will not fit flush, or may not attach at all. As you can see, the jute pad has to be cut into portions to fit the curves, so it looks like a piece-meal job, but it has to be. But the important thing is to cover as much as you can. I used the same adhesive for these parts too.


    This is just one panel, but this was done to all 4 panels.
    Take a close look at the very edge of the panel. I had a feeling that these parts were rubbing against each other and making noise, so I went to Lowes and got some 1/2" wide foam insulation, usually used for home use (door jambs, windows, etc). This stuff is self-adhesive; just take off the backing and apply. I also used this on the speaker assemblies.

    A few more things:
    *I also used the spray expanding foam on the inside of the hatch behind the license plate, and removed the little rubber grommets and filled the edges of the hatch on either side of the rear window.(put those grommets back on while the foam is still setting!)
    *Expanding foam also went...ready? into the rocker panels! I found that one of the reasons the really expensive cars (Bentley, etc) are so quiet is that foam is used in the rockers, the A pillers, etc, etc. I couldn't do everything, but I wanted to do the rocker panels.
    * I put small rubber grommets on the rear of the license plate to prevent rattles.
    * I re-undercoated the wheelwells with 3M rubberized undercoating
    * the jute pad with the foil backing was used as far under the dash as I could get.
    * the original fiberboard spare-tire cover was replaced with a custom made 1/2" plywood version, also insulated with the black jute.

    So.. thats it.
    The big questions are: how much did all this cost and does it work?
    Price for all materials was about $150. This was about 6 yards of the black jute, 3 yards of the foil-backed jute, the spray foam (about 5 cans), spray adhesive, the thin foam strips used on the panel edges, and 3 rolls of the roofing flashing I used instead of Dynamat. (I got this stuff at a local TruValue hardware store; the local Home Depot or Lowes does not have it)

    How does it work? Really well! It's not a Lexus, but it makes a big difference. I do not have a sound decibel meter, but it is noticeably quieter in the car, especially when I have all the windows closed. Where before I had to put the radio on sound level 45 to hear it to my satisfaction, (I only have two speakers, both in the rear) now i can set it to 40. Also there are no rattles coming from the rear cargo area! This confirms what I thought about the plastic panels rubbing, not only on each other but the metal structure of the car as well. It really does make it easier to drive, since all that road noise can make me mentally tired after a while.

    All in all, I think it's a worthwhile project, and would only take a weekend or less.
    If it has boobs or wheels, sooner or later you're going to have trouble with it.
    Mark S.

  • #2
    Great write up! A couple of questions though.
    How well did the inner panels fit back together and in place once you put the backing material on them?
    How did you spray the foam into the rocker panels?
    Search Master - Honorary Member of Midwest Festiva Inc., Gulf Coast Chapter

    Everyone is entitled to be stupid, but some abuse the privilege.
    - Unknown
    I don't like superstitious people. They're bad luck. - Serge A. Storms

    If at first you don't succeed, failure may be your style.
    - Quentin Crisp

    God, please save me from your followers!
    - Bumper Sticker

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    • #3
      I've got another question, how much weight did this add to the car?
      2005 Mitsubishi Lancer Ralliart
      1991 Ford Festiva LX
      1989 Mazda 323 GT

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      • #4
        WOW!!! awesome project and great job.....outstanding
        Ski

        1986 Ferrari Testarossa
        2002 BMW 745i
        2002 BMW 325i
        1989 BP'd Festi :p

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        • #5
          +1 on the weight question.
          91GL BP/F3A with boost
          13.79 @ 100, 2.2 60' on 8 psi and 155R12's

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          • #6
            Absolutely awesome. This is going into my future projects. Thanks for the detailed pics.

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            • #7
              If you remove the rocker moulding that hold the edge of the carpet on the door jamb, right underneath it there are small holes that I used to spray in the foam. I probably didn't fill it all the way, but I know it's quite a bit. The thing is, you can't see inside there to see how much the foam has expanded, and therefore how much more to put in. It's a big guess.

              For the weight, I really didn't weigh it, (probably should have), but after thinking about it, I would estimate the weight of all the materials at about 25 lbs., and probably less than that. I used lots of that black jute, but it's actually pretty light even though it's dense. I removed my rear seat and seat belts long ago, so if the rear seat is about 35lbs, I am still ahead of the game.

              BTW, sorry about the huge pics; I thought I had reduced the size enough. But at least you can get a good look at everything.
              If it has boobs or wheels, sooner or later you're going to have trouble with it.
              Mark S.

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              • #8
                Ooops, the other question!
                The rear panels actually fit fine, no problems. That jute pad is thick enough and dense enough that it is laying right against the metal panels. I could feel the resistance of the jute being SLIGHTLY compressed as I installed them, so I think it was just the right thickness.
                You will note on the pic of the panel that there are places, near the very edges, that are bare, because if you put foam on those places, the panel would not fit right imo. But I didn't know until I did it. Much of it was: apply jute, test fit. Apply jute, test fit, etc etc.
                If it has boobs or wheels, sooner or later you're going to have trouble with it.
                Mark S.

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                • #9
                  Excellent job and excellent write-up Deathegg!

                  I'll definitely be referring to your methods and considering your materials for my own work when I redo Luxtiva, and put a little extra comfort into Twinstiva/Speedstiva.

                  Thank you!

                  Karl
                  '93GL "Prettystiva" ticking B3 and 5 speed, backup DD; full swaps in spring!
                  '91L "AquaMutt" my '91L; B6 swap/5 speed & Aspire brakes, DD/work car
                  '92L "Twinstiva" 5sp, salvage titled, waiting for repairs...
                  '93GL "Luxstiva," '94 B6 engine & ATX; needs overhauled
                  '89L "Muttstiva," now a storage bin, future trailer project

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                  • #10
                    great info. any specifics on the roofing flashing so i can get some?
                    92 Festiva - 1.3L 5sp work in progress DD
                    87 MJ - 4.0L AX-15 231 Dual 44's with Detroits and 4.56's TnT Long-Arms and 35x12.5 Claws

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                    • #11
                      One of the main products out there that can be used instead of Dyna-Mat is called Peel and Seal, by a company called MFM Building products. I couldn't find that here in SoCal, So I went to the nearby Tru-Value hardware store, and got a few rolls of a similar product, but can't remember the name. I think if you go to a Lowes or Home Depot, etc, and go to the roofing section, something of that type will be there.
                      If it has boobs or wheels, sooner or later you're going to have trouble with it.
                      Mark S.

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