Engine sound pad does it do any good? - Page 2

KTL · 04:03 PM

The early cars may not have as much sound deadening as the later cars. I know my car has a very thick rubber-topped interior sound pad that is on the interior of the car, behind the rear shelf and firewall, which has to be blocking the vast majority of the sound from the engine bay. I took my interior padding out and noticed a bit more road noise, but the engine sounds did not seem to be overly increased.

My engine bay pad is starting to come down and since I have my engine out this winter to fix a cam/chain box leak and a crank pulley leak, I will be pulling the engine pad out and will find out the difference. A friend has all this removed from his '86 coupe (with B&B single out header system) and I don't recall the sound being unacceptably loud when riding in his car.

Removing the old glue is best done with an organic adhesive remover or engine degreaser. A friend got all the glue off his quite easily with a degreaser made by Ricmar that is biodegradable and very friendly to you and your paint. He sprayed it on, let it set for a little while, wiped it off. After two applications, you'd never know the glue was ever there.

jtfreels · 02-22-2007, 04:26 PM

Thanks for the opinions guys. Noise.... I had to wear ear plugs any way when I drove long distance time, Targas are noisy beasts. How it effects the heat is a decider. But the biggest is that nasty glue, like Dan I don't have the time to spend to get that off, unless the stuff Kevin refers to is something I can try tomorrow.
The engine IS going in this weekend.

On thing I've discovered in my short Porsche ownership, it's MUCH worse to have a Porsche you can't drive, than not having one at all.

Jay

hcoles · 02-22-2007, 05:23 PM

I finally got all the old glue off and put two layers of stuff I got from a place in Canada... I think the company used to be Brown Bread..
I can dig up the info. if you want. My old sound pad was shot I would say the new pad set is a definate improvement.... there is still the whine but if just cruzing the noise is not bad at freeway speeds...

bigchillcar · bigchillcar's Garage

as long as your pad isn't disintegrating, as mine was, doesn't much matter either way really. but if it is disintegrating, you don't want loose bits of foam working their way into your intake..my primary concern with very old pads. i had to drape a sheet over my engine when i removed it as it was literally raining thousands of tiny bits of rotten foam.

Mysterytrain · 02-22-2007, 05:43 PM

I had the new version of the sound pad in my car. The grey didn't look so hot on a black car so I tired to replace it with the old original style from our host..after shipping me 3 pads we found out that the old style black pad was no longer available. I wound up making my own with some 1" black foam that I got from work. I used the old pad as a template. Looks great.

imcarthur · imcarthur's Garage

As above I replaced it to hide the glue. Standard stock one from Pelican. And yes, even in a Cab it makes a very noticeable reduction in cabin noise.

Ian

AL MEREDITH · AL MEREDITH's Garage

I bought a peace of aluminized fabric from JC Whitney. Made a template and cut a new one . Took it to a trim shop and had a black border sewn around it. 3Med it in ...looks great. I had enough material to make 3. So I have two extra pads if anyone wants one $50 I'll pay freight. Al ljgmere@aol.com if you need pictures. Al

randywebb · 02-22-2007, 08:46 PM

Quote:

Originally posted by 1974carrera
The purpose of this pad, at least the oem one, is thermal insulation. The new one (oem) I installed is a closed-cell foam and weighs much less than one pound. Its density is so low I can't imagine it could do much to attenuate sound.

You are correct about the weight, but are conflating density with sound attenuation. Put a new pad in; it significantly attenuates noise, and serves as a thermal barrier as well.

Use the aluminum faced stuff if you believe that the engineers at JC Whitney are significantly better than the ones at Porsche AG....

jtfreels · 02-23-2007, 04:59 PM

Update...., I left the pad in the car. Got some glue that worked and glued it back in place. It was the easy way out!

Jay

1974carrera · 1974carrera's Garage

Quote:

Originally posted by randywebb
You are correct about the weight, but are conflating density with sound attenuation. Put a new pad in; it significantly attenuates noise, and serves as a thermal barrier as well.

Actually, I do think I am conflating density and sound attenuation just a bit...and perhaps you will too if you consider the mass-density law, an approximation which indicates that the heavier the material the better it insulates sound.

Generally, the mechanisms for reducing sound depend on where the sound originates relative to where you are listening from. For example, if the sound is generated within a room and you are listening from within the room, then sound can be absorbed to achieve some attenuation. If the sound is originating from outside, then to keep sound out it is necessary to insulate the space you are listening from.

Cellular and porous solids can be good absorbing media, but they are not very good at insulating against sound. Typically, foam materials are not good at providing insulation from sound. Again, the degree of sound insulation depends on the mass-density law...the heavier the material the better it insulates sound.

Considering these general concepts, I can see how the oem foam pad inside the engine compartment could absorb some sound, although it still seems, to me, that its porous, foam structure best serves as thermal insulation. On the other hand, a primary purpose of the dense pads on the passenger side of the firewall and underneath the rear seats is to insulate the passenger compartment from sound occurring outside the passenger compartment. It seems to me that Porsche got it right: a good thermal insulator and some sound absorption in the room with the sound and a sound insulator in the room adjacent to the sound.

Quote:

Originally posted by randywebb Use the aluminum faced stuff if you believe that the engineers at JC Whitney are significantly better than the ones at Porsche AG....

You must have confused my post with another as I never mentioned JC Whitney nor any inane comment suggesting that the Whitney engineers are significantly better than the P AG engineers?!? And no thanks, I'm not using the aluminum-faced stuff. I chose the oem pad when it came time to replace. You say a new pad "significantly attenuates noise"...I am certainly not refuting your individual experience, but as another reference I will say I ran my engine without the pad in the engine compartment and, subsequently, with the oem pad in place (see pics below) and I couldn't tell the difference in sound in the interior. Maybe that's due to too many years of rock 'n roll when I was younger and too many years with a sport muffler as I've gotten older :-) .

Larry_Ratcliff · 02-26-2007, 07:37 PM

I went without in my 74. But I love to hear my engine. I dont even have a stereo just a radio delete plate .... no need for tunes with the sound of perfection roaring in the rear

Larry_Ratcliff · 02-26-2007, 07:44 PM

Quote:

Originally posted by 1974carrera

On the other hand, a primary purpose of the dense pads on the passenger side of the firewall and underneath the rear seats is to insulate the passenger compartment from sound occurring outside the passenger compartment. It seems to me that Porsche got it right: a good thermal insulator and some sound absorption in the room with the sound and a sound insulator in the room adjacent to the sound.

I ditched the back seat insulation along with the rear seats too... put in a RS rear seat delete set and stuffed the back seat full of roll cage

BTW looks like a sweet car you have there.