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Thread: Sound insulation install, with pictures!

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    Hubcap Enthusiast Scratchpaddy's Avatar
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    Sound insulation install, with pictures!

    I just finished installing vibration damping and sound insulation all over my Mirage. I did it as a fun project, a few hours each weekend morning. It took a month in all. I really took my time.

    First, I removed everything from the interior, except the dashboard. I may go under the dash eventually, but I didn't feel like doing it just yet.

    The floor has some asphalt patches applied from the factory for some limited resonance control. It's a cheap way to make the floor seem a bit less boomy. The asphalt tends to get brittle and come loose over the years, so I figured I'd take them off now and replace them with my own damping material while I had the carpet out. They were pretty easy to pull up.



    They did leave some asphalt residue behind, which I cleaned off with acetone.



    The first step in reducing noise in a car is damping vibration in the metal panels. The most effective way to do that is to make a sandwich of two stiff materials, with a viscoelastic layer in between. It's called "constrained layer damping," or CLD. Dynamat is the brand most people know of, like the Kleenex of automotive vibration damping. One stiff layer is the car's sheet metal, the other is a thin aluminum sheet, and butyl rubber adhesive makes up the viscoelastic layer in between.

    There's a lot of misunderstanding about how Dynamat-type products work. A lot of people think it's sound insulation. It's not. It blocks nothing on its own. But, when adhered to a metal panel, it makes that panel more resistant to vibration. It also lowers that panel's resonant frequency, making it less transparent to the most irritating high-frequency noise.

    People also like to cover every square inch of metal with the stuff, or even apply multiple layers, which is a huge waste of effort, money, and weight. CLD materials are most efficient when they cover about 25% of the metal panel's area. Covering everything does give a little more damping, but the benefit falls off fast after 25% coverage.

    I had a little bit of material left over from another car I did, from Sound Deadener Showdown. It was the best stuff around, but Don, the guy running the shop, just retired early this year. So, no more good ol' SDS CLD tiles. I went with KnuKnoceptz Kno Knoise Kolussus (what a name!) for the rest of the car, which testing on the DIY Mobile Audio forums showed was nearly as good. I only used about two-thirds of the 35-square-foot box I bought to do the whole car.



    I did the doors first, but only the outer skin. The inner skin isn't much of a concern with all the window hardware bolted to it, and the door card pressing against it.



    I found 65 to be the ideal temperature for peeling back the plastic dust covers from the inner door skin. The butyl was flexible, but not gooey, and pulled away from the metal cleanly at that temperature. I tried it on a 100 afternoon first, and it was a gooey mess.

    Thick, stiff structural members like the B-pillars are already sturdy enough that CLD material is of no benefit. I went around knocking on everything, and if it already sounded like a block of wood, I left it alone. The roof and the outer door skins benefited hugely from the CLD tiles. The red and blue areas of this graphic were already solid as a rock.









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    Hubcap Enthusiast Scratchpaddy's Avatar
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    At this point, if I were really serious, I would move on to making a mass-loaded vinyl (MLV) barrier, but I went with lighter sound-absorbing insulation instead. Insulation is not a direct substitute for a sound barrier like MLV; ideally, you'd use both. But, space is limited in a car, and the extra weight of MLV is noticeable in a car this light. Plus, there's the expense and hassle of working with MLV. I've done it before on my Metro, and I didn't think the benefit was worth all the extra cost, effort, and weight.

    I went with 3M Thinsulate SM600L for most of the car. It's a thicker version of the same Thinsulate used in high-tech lightweight winter clothing. 3M mostly sells it to OEMs, but there is an RV outfitter in Oregon who sells rolls of it through Amazon and eBay, as it's very popular with the conversion van crowd.

    It's more expensive than standard automotive jute, but it's hydrophobic, so there's no need to worry about it soaking up water. Plus, it's insanely lightweight, and very easy to work with. It's sold in 5-foot-wide rolls. I bought 10 linear feet, so 50 square feet. It was enough to do the doors, quarter panels, hood, and the roof. It's too thick to go under the carpet.

    The SM600L I bought is 1.75in thick when fully lofted. There's also a SM400L which is only 1in thick. You can compress it down to almost nothing if needed, but the more it's compressed, the less effective it is at absorbing sound and blocking heat. It turned out to be pretty much the perfect thickness for between the headliner and the roof.



    There are little styrofoam standoffs all over the top of the headliner. The Thinsulate fits neatly into the air gap enforced by those standoffs.



    It felt good to finally start putting parts back into my car at this point. It was an empty shell for weeks.



    The door panels do come with some jute insulation from the factory. I think they added it mostly to keep the plastic from rattling against the metal, as they didn't use enough to really absorb much noise. There's so much room inside those door cards, I kept the factory jute and added the Thinsulate right on top of it.





    The big trim panels covering the rear wheel wells and quarter panel had a little less clearance. I had to remove the larger of the two stock jute pads. They're fastened with light adhesive, and pull off easily. I re-purposed them for that board covering the spare tire. I had just enough Thinsulate to do under the hood, too. The stock hood pad leaves a pretty big gap between it and the metal.




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    Hubcap Enthusiast Scratchpaddy's Avatar
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    After using up all my Thinsulate, I moved on to regular "jute". Technically, jute is a plant fiber similar to linen or hemp. What we call "jute" in cars has nothing to do with it. It's a bunch of discarded textiles (carpet, clothes, rags, etc.) shredded up and bonded into a loose pad. There's a company called Bonded Logic that sells it through Home Depot, so that's where I got mine. I later found out that their manufacturing plant is just a few miles from where I live.

    Their 3/8" thick 48in x 6ft radiant barrier, meant for covering ducts and dishwashers and such, turned out to be the perfect size for the Mirage's floor pan. It's my understanding that a radiant barrier doesn't work without an air gap, so the aluminum actually has no effect here, but all I wanted was padding to make the floor a little softer and less hollow-sounding when you stomp on it. This did the trick, though carrying a 4-foot-long box home on my bike was... interesting.



    I bought their 1.8" thick pads for the remaining space in my car. It's not as easy to cut as Thinsulate, and it's a little bit dusty, but it's miles better than fiberglass or rockwool, and it's pretty cheap.

    There's a surprising amount of space above the rear wheel wells between the inner and outer skins of the car body. I stuffed it full of insulation. I did the same to the rear hatch. The little bit of extra weight didn't bother the gas springs; it still opens on its own.



    I put a nice lining around the spare tire. Then, for good measure, I added a whole layer between the cover board and the fabric mat on top, which already comes with its own thin layer of jute from the factory.




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    I'm pretty pleased with the results. It wasn't that expensive, and the weight added is negligible. It's still not a Lexus, but it's much improved. I took it on the highway at 70 mph, and I could easily understand the news with the stock radio at 25 (I think it goes up to 40?). The doors sound absolutely solid. It seems like such a small detail, but just the quiet click of the latch, and the gentle thunk the doors make when they're closed makes the car feel 4x as expensive now. I was worried that I'd somehow broken my power locks at first, because they hardly make a sound anymore.

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    Senior Member dspace9's Avatar
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    Quote Originally Posted by Scratchpaddy View Post
    I'm pretty pleased with the results.
    That is some project to tackle. Any mods on my own Mirage have to wait until I have another car. My Mirage is my daily driver. One day my little Mirage will be a summer car. That day has not come, but all I plan on is some sort of custom exhaust, and maybe new speakers one day.

    The 45 max volume on my Mirage isn't loud enough when the windows are down in the summer, especially on the AM for baseball games.

        __________________________________________

        click to view fuel log View my fuel log 214 Mirage ES 1.2 manual: 39.8 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.8 mpg (Imp)


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    Scratchpaddy, that's a great project and I really appreciate how you've documented and shared it here with us. Great pictures too.

    Thanks.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.9 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 59.9 mpg (Imp)


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    Quote Originally Posted by Scratchpaddy View Post
    There's a lot of misunderstanding about how Dynamat-type products work.
    CLD materials are most efficient when they cover about 25% of the metal panel's area.
    I was watching a show on TV where they were applying Dynamat to a DeLorean. Those guys applied it the same way you did. They didn't cover everything. It's interesting how a small patch of Dynamat can keep an entire body panel from vibrating. I definitely did not understand that until I saw that show.

    Awesome write-up! For another $100 of materials, Mitsubishi probably needs to do this at the factory on all cars headed to the US market.

    I have to take my mom on a 4-hour road-trip here in a couple of weeks. She asked me if we were taking my car. I just laughed and said no...we'll be taking yours because it's so much quieter. She has a 2019 Honda Pilot.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 51.7 mpg (US) ... 22.0 km/L ... 4.5 L/100 km ... 62.1 mpg (Imp)


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    Hubcap Enthusiast Scratchpaddy's Avatar
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    Quote Originally Posted by dspace9 View Post
    That is some project to tackle. Any mods on my own Mirage have to wait until I have another car. My Mirage is my daily driver. One day my little Mirage will be a summer car. That day has not come, but all I plan on is some sort of custom exhaust, and maybe new speakers one day.

    The 45 max volume on my Mirage isn't loud enough when the windows are down in the summer, especially on the AM for baseball games.
    So, you want your Mirage to be louder, not quieter? I may get new speakers for mine at some point, but I really don't use the radio that much. I don't even try if the windows are open.

    I've gotten used to going months at a time without a car, or without a working car. I work less than two miles from where I live, so I ride my bike there every day. I've actually never driven to my current job, which I've had for two years. I have an old Fuji that I've fitted with flat bars, a rack, and pannier bags for getting groceries. It gets the job done, but it is nice to have my car back. Today I picked up a 45lb bag of dog food in the car. I can't get bags any bigger than 15lb when I'm limited to the bike.



    Quote Originally Posted by Eggman View Post
    Scratchpaddy, that's a great project and I really appreciate how you've documented and shared it here with us. Great pictures too.

    Thanks.
    You're welcome!

    Quote Originally Posted by Top_Fuel View Post
    I was watching a show on TV where they were applying Dynamat to a DeLorean. Those guys applied it the same way you did. They didn't cover everything. It's interesting how a small patch of Dynamat can keep an entire body panel from vibrating. I definitely did not understand that until I saw that show.

    Awesome write-up! For another $100 of materials, Mitsubishi probably needs to do this at the factory on all cars headed to the US market.

    I have to take my mom on a 4-hour road-trip here in a couple of weeks. She asked me if we were taking my car. I just laughed and said no...we'll be taking yours because it's so much quieter. She has a 2019 Honda Pilot.
    They actually did a pretty good job for such a cheap car. The door seals are excellent, for one, and they did go through some effort to keep rattles at bay.

    Besides, if they made a cheap, efficient, reliable car that was also quiet and pleasant to drive, why would anyone spend more for a luxury car? Gotta maintain the market segmentation!

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    Quote Originally Posted by Scratchpaddy View Post
    I have an old Fuji that I've fitted with flat bars, a rack, and pannier bags for getting groceries.
    That's a pretty bike. You'll have to tell more about it. Looks like a Brooks B-17 and I admire the downtube shifters. Those brakes are not stock?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.9 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 59.9 mpg (Imp)


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    Senior Member dspace9's Avatar
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    Quote Originally Posted by Scratchpaddy View Post
    and they did go through some effort to keep rattles at bay.
    For sure, everyone's situation is unique, and different. For my life, my Mirage is my commuter car, a 10 mile commute each way to work. I'm in Canada, too. And real estate prices in my town, compared to where I work, makes the commute basically necessary.

    Talking about the loudness of the Mirage, the Mirage is a loud car. Not if you're being super gentle it idles actually quiet, but revving it, wow look out. Vroom! One of my coworkers thought the car is a diesel.

    On the musical side of things, I'm a 24/7 music person, so not sure if my Mirage's stereo has actually ever been off lol.


        __________________________________________

        click to view fuel log View my fuel log 214 Mirage ES 1.2 manual: 39.8 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.8 mpg (Imp)


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