engine compartment sound pad alternative?

robphelan · 06-04-2003, 08:17 AM

Has anyone used an aftermarket sound pad for the engine compartment? PO took mine out and it looks terrible without it.

Any suggestions on where to find one? What material is it made of?

Thanks,
robphelan

norustscott · norustscott's Garage

I used the High Temo Dynomat...Took out the stock pad...cleaned everything. installed the Dynomat and then spent about 2 hours removing the hairy crap off of the rubber stock mat...I cleaned the rubber mat up and reinstalled it over the Dyno mat. looks stock, without the mess.

maf 914 · 10:34 AM

Scott,

Is the original mat a rubber mat with a horse-hair layer attached? Or is the hair mixed in with the rubber? Were you able to remove the hair layer or just clean it up? I am about to attack mine and was wondering what to expect.

Mike

Dynomat website: http://www.dynamat.com/

robphelan · 06-04-2003, 10:40 AM

the problem is that I don't have the original pad to make a template from - or to stick the dynamat onto.

Do I just buy a bunch of the dynamat and 'go at it' to the firewall? If so, will it help much without the original pad?

maf 914 · 06-04-2003, 11:11 AM

Will Dynomat help much? Good question. Does the original pad do much? I don't know, but I think I am going to find out by removing the ratty pad from my car.

Do a search for Dynomat or sound pad or sound absorbtion and you will see that this has been discussed many times in the past. There are several ideas and some alternatives to Dynomat in the posts.

Mike

norustscott · norustscott's Garage

I will take a picture and post later this evening...

norustscott · norustscott's Garage

Actually looks better than the pictures:

sean_V8_914 · sean_V8_914's Garage

Mike's 2.0 is much louder inside while driving down the road without the stock pad as compared to my 1.8 with pad installed

ss6 · 06-06-2003, 09:40 AM

I used the aluminum lined Dynamat on the engine side of the firewall like Scott did, but without the stock pad. Looks good, and I think the goo on the Dynamat pad will protect the firewall from corrosion quite effectively.

Despite addition of other Dynamat stuff on the inside of the firewall plus a layer of carpet on top of that, it's still pretty noisy inside. Could be the six and the bulkhead mount, but the noise level is also highly dependent on what kind of air cleaner you are running, and how well your rear window is sealed.

scotty914 · 06-06-2003, 09:46 AM

i have a stock sound pad that is not ripped but needs the fiber stuff cleaned off if some body needs/wants it

sean_V8_914 · sean_V8_914's Garage

John, your right on about sound levels and sealing the rear window. I just did my rear window and it is much better now.

tod914 · 06-06-2003, 10:07 AM

I think AA has a repro of the matt. I cant vouch for the quality of it.

ss6 · 06-06-2003, 12:26 PM

Sean, how did you get the rear window out in the first place?

sean_V8_914 · sean_V8_914's Garage

I think I read this on Pelican, but I could not find it for you so here it is. Back window comes off to the inside of the car. it requires taking apart alot of little trim pieces but it is relatively easy First remove the seats. 2 remove seat belt bolts. 3 remove vynil side trim pieces on teh inside B pillars. 4 remove the engine opening handle. 5 remove the four screws that secure the back pad. 6 remove center console tray or cushion. 7 pull the back pad out about 2 inches and then down about 2 inches. this will release the two hooks that hold it against the top of the fire wall. If things do not come apart easily, make sure all the screws have been removed. Once all this stuff is out of the way, the sealing area will be easy to pick at. gently push the window out starting from the loose areas first. you might need to use a thin wire to cut the previous glue away. good luck. I have better instuctions somewhere. I can send them to you when I get back from biz trip next month. have fun, good luck

mike95125 · 06-06-2003, 09:59 PM

Seans right. My 2.0 is loud without the pad, and also because it has a bad lower window seal. I'm used to it though because I usualy ride a motorcycle.

red-beard · red-beard's Garage

What? I can't hear you mike. Can you speak up a bit?

James

KWales · 06-07-2003, 06:31 AM

OK,

Thought I would post a little about noise reduction since no one else seems to know what works. Learned this many years ago when I designed and quieted dot matrix printers. Those of us familiar with them, know that they are very noisy. (Dating myself again!)

There are two sources of noise, direct transmission through an opening, and secondary transmissions through a wall. The teener engine compartment with it's open engine grilles has several direct noise transmission paths. The drip pan probably helps as a noise baffle, but not very much. The bulkhead wall has sound absoorption materials on 2 sides to dampen noise.

The engine compartment is a metal box with hard walls and sound reflects around vey well in there. To quiet the noise, you can do two things: block the noise source with a hard surface (block off your grilles and go for overheat) or place some absorbing material in the engine compartment.

To absorb some of the noise, high density noise foams work well. Sound is absorbed as it burrows into the foam and as it is reflected off of the hard surface that the foam is attached to. Sometimes they add a sheet of silvered mylar on the surface to absorb high frequencies and in an engine compartment this can acts as an oil barrier too.

The best way to absorb sound is to use a mass that the sound can excite, and a spring like material that couples the mass to a hard surface. As the mass is excited by noise, it moves, and the spring absorbs and dampens the sound energy. That pretty much describes the sound pad that porsche engineers developed with the black surface acting as both a mass and as a sound barrier, and the fuzzy stuff as the springs. After 30 years, the glue on the fuzzy stuff has degraded to the point where it doesn't work anymore.

What I plan on using is a sheet of sound deadining material that has a foam surface that can be glued to the firewall, a mass such as a vinyl or lead sheet glued to the foam, another layer of foam glued on top of the mass to absorb sound, and a mylar coating glued on the outside to absorb high frequencies and repell oil. This stuff is regularly sold for industry in rolls with a peel off liner on the glue. The best stuff that I have used has lead encased in the vinyl. More mass definately helps.

Adding a layer to the rear firewall might help also as that surface is a hard reflection surface and making it a "dead" surface would stop sound from reflecting forward.

Hope this helps

Ken

maf 914 · 06:52 AM

Ken,

Good explanation. Do you have a particular product in mind to meet your described specs? Do you thing the Dynamat products would do? They have an engine hood blanket listed as a standard product, but it is shown in a horizontal application (front engine hood).

http://www.dynamat.com/

McMaster Carr lists some multilayer products also. Search for "sound absorbers".

http://www.mcmaster.com/

Mike

KWales · 06-07-2003, 08:16 AM

Mike,

McMaster Carr doesn't have the right stuff. Most of the Dynamat products are for preventing resonance in large flat panels (floors, hoods, etc.).

The Dynamat Xtreme looks to be their best sound absorbing choice as it has the shakable lead barrier, the dampening layer and the absorption layer. For perfection it could be a little thicker (at only 3/8").

I used to use products from a company called Soundcoat.

Ken