Sound deadening works too well

RallyJon · 03-08-2003, 06:26 PM

Nice day in Philly--50 and sunny--so I took the 911 out for its maiden voyage after redoing the interior.

I had driven it completely stripped to my mechanics to have the rust repairs done about six weeks ago, and was stunned how loud it was without the rear seat padding. I don't mind loud cars, but it had some seriously unpleasant boomy resonances. Before putting in the carpet I laid down a single layer of leftover Dynamat Extreme followed by a layer of B-Quiet Lcomp. I figured it weighed about the same as the pad I removed so it would be about the same noise deadening, right?

Um, wrong. There is now almost no perceptible noise coming through the firewall. The only engine noise I can hear is the Webers' intake sound and the exhaust noise coming in through the roof vent and the windows. It's eerie.

So if you're looking to quiet down your 911, this stuff really works. As for me--maybe I'll drill some holes in the muffler or something...

Here's the Dynomat layer

Here's the Lcomp layer

And here's a cross section of Lcomp

Elombard · 03-08-2003, 07:10 PM

Who sells the B quiet?

Schuey · 03-08-2003, 07:14 PM

where did you get this stuff?

speeder · speeder's Garage

Well, I'm one who believes in sound deadening in that particular place, IMO you want to hear the exhaust note of the car, not the valve train through tin.

Sounds like you might have overdone it a little, but nice to hear how well that stuff works.

john_colasante · 03-08-2003, 07:19 PM

What you did is more or less what 993's have stock. They have very think padding in the rear, tunnel and floors.

cowtown · 03-08-2003, 07:33 PM

RallyJon,
Could you let us know how much Dynomat you needed to cover this area? I'm interested in doing exactly what you did. My '75 is deafening without any sound insulation.
Thanks,
Colin

Todd Simpson · 03-08-2003, 08:20 PM

I gotta get some of this so I don't have to hear my 901 ring and pinion *howl* at any speed above 40 mph.

RallyJon · 03-09-2003, 01:06 PM

I had Dynamat Extreme lying around so we used that mostly, but I also got a roll of B-Quiet's competitive product, called Brown Bread. Despite the stupid name, the Brown Bread looks to be nearly identical to Dynamat Extreme, except it's more pliable and cheaper.

B-Quiet is a Canadian company and they sell direct at www.b-quiet.com

As for quantity, it took about 15 sq feet. The Dynamat/Brown Bread is a deadener, not a barrier, so it doesn't matter of you piece together lots of scraps.

The LComp barrier should be used in the largest pieces possible, because every seam is a place where sound can come through. I used 2 packages (@8 sq ft each) of LComp and had about 2-3 sq ft of left overs.

It's really not very thick: 1/2" of LComp and 1.14 mm for the Dynamat.

island911 · 03-09-2003, 01:46 PM

Excellent posts, Jon.

Why did you install it on the cabin side of the engine bay? (as opposed to in the engine bay)

RallyJon · 03-09-2003, 01:57 PM

The LComp isn't heat resistant and doesn't have an aluminized layer. I think B-Quiet has a hoodliner type product that might work in place of the engine sound pad, but it doesn't have the decoupler.

Dave Ploss · 05-14-2003, 01:54 PM

Rallyjon,
I'm going to be doing exactly what you did this weekend. I've taken out the rear seats and carpet but I have one question.
Do you put the black plastic with the felt on one side back in or do you leave it out after putting in the brownbread and bquiet?

I sure hope the answer is that you leave it out, but I don't think so.

Please let me know what you did.

Thanks.

Dave

RallyJon · 05-14-2003, 02:00 PM

Quote:

the black plastic with the felt on one side

Do you mean the rear shelf? If so, I left it out and cut off the mounting tabs with a cutoff wheel.

If it's a side trim piece and will fit over the carpet, you could go either way. I added back the panels that cover the inertia reels, but left out the full side panel.

Dave Ploss · 05-14-2003, 02:14 PM

I'm talking about the big heavy thing over the rear shelf. I'll leave it off. I was planning on putting the side trim pieces back on.

thanks. Can't wait to see what it does.

Dave

RoninLB · 05-14-2003, 02:40 PM

Quote:

Originally posted by Dave Ploss

. Can't wait to see what it does.
Dave

IMO, it kinda helps eliminate the tin can sound.. and makes the engine and exhaust sound cleaner.........Ron

beepbeep · 05-14-2003, 03:48 PM

What sound deadening?

expat · 05-14-2003, 04:22 PM

Jon,

Thanks for the post...timely. I tore out all my sound deadner a while back and I cant believe how much heat is getting transferred through the tin work so I'm going to put it all back in. Thanks for the link too.

Cheers
Mark

89944TurboS · 05-14-2003, 04:28 PM

Great job! I am all for the sound stopping too!

jyl · jyl's Garage

How much does it weigh? And do you see (hear) the need to put the Dynamat on the floor as well, or is the rear firewall enough? Assuming you don't want an isolation chamber, but just a car quiet enough to enjoy music and converse in a moderate voice.

fogcity · 05-14-2003, 07:42 PM

How hard is it to remove the seats, pannels, carpet from the back? I might like to lessen the ringing in my ears as well.

k9handler · 05-14-2003, 08:09 PM

well....I like mine loud!
But that's just me.