Reducing sound
filed in 1999 Honda Civic
Question: I know most folks think JC Whitney is a merchant of junk, but they do have some nice aftermarket accessories.
You may be able to find a low cost underhood insulation blanket that will be far cheaper than a manufacturer specific one that you have to cut down anyway.
Another trick is to get some sound deadening pads from an automotive paint dealer. This look like 12 x 12 self stick floor tiles. You trim them and paste them onto the sheetmetal. The effect is amazing. One brand is called “Q-Pads”. I just got some generic ones made by 3M.
Take of th inside trim like on the doors and other quarter panels an stick on the pads and replace the trim. I put them under the carpet and under the seats wher there is typically not any carpet or insulation.
Also put some insde the hachback door. Another trick a friend used was expanding insulation foam, sold in spray cans. He filled all the empty channels and spaces between body panels with the stuff. It really killed the noise but was a pain to get it in and then have to trim off all the place where it expanded too much
Answer: My friend’s got a 1988 Honda Civic hatchback… It’s not in the best shape, but it’s nice. One thing we’d like to do, though, is reduce the amount of noise from the engine and outside that gets into the passenger compartment.
My 1984 Mercedes 300D has sound (and maybe also heat) insulation on the underside of the hood. It’s a huge single piece of absorbent material of some kind. I was thinking we might be able to buy that and cut it to the right size and put it on the underside of his hood and/or on the firewall (if there’s space).
Would that work? Is it safe?
What are other options to look into?
You can’t make a silk purse out of a sows ear. My brother has an 86 300D and I’ve driven 88 civics. There is just no comparing these two cars. You’d think the 300D would have a noisy engine but you can barely hear it inside the car (windows up). OTOH, an 88 civic has a buzy resonating little non balance shaft 1.5-1.6 liter four banger. I’m not saying the civic is not a quality car but it’s a basic transportation ride. Adding insulation under the hood might help a tiny bit but what about the dronning resonances and intake howl from the small air box and snorkle. Besides most the engine / road / tire noise is coming into the passenger box via it’s thin, non insulated packaging. I think the hood is basically irrelevant to sound. To quiet down the driver’s compartment, you could pull out the carpet and put an extra layer of sound absorbent material down there. Put some dynomat in the doors, and pull down the headliner and put sound insulation up there. The 300D might also have a double firewall with two separate insulation layers (the Olds diesels sure did).
Look at it this way: A basic Dodge minivan costs $17,000. A Chrysler Town and Country LXI costs $36,000. The metal body is exactly the same. So they make them sound different by hiding sound insulation everywhere they can. Just think about where you could hide it. P.S. Dynomat is expensive.
Want to give your own answer? Want to comment?