Installing some new carpet: Dynamat over top OEM sound deadening?

[aread]

Originally Posted by mickey356

If the rust is in the usual place, rear passenger seat bowl, it's a fairly simple patch job....accessible from top and bottom, and depending on the size, weld a piece of metal or buy a pre-cut piece from salvage or a re-pop.

What I'm trying to wrap my head around is how to get the carpet to lay smooth with all the recommended layers of dampener and deadner. It seems like there would be a lot of cushioning and therefore difficult to get a clean look.

Thanks Mickey. And your right, in the grand scheme of rust, this could be alot worse.

With regard to the carpet laying smooth, I'm wondering if the extra padding might make it easier and more forgiving for some of those awkward corners and curves (This is probably just wishful thinking)

[Quicksilver]

Originally Posted by john walker's workshop

Dry ice and a rubber mallet.

I've always wondered what that will do to the undercoat. Does that stay on?

[mickey356]

Originally Posted by Quicksilver

I've always wondered what that will do to the undercoat. Does that stay on?

There was a video of someone using dry ice on the floor coating...pretty impressive how it made quick work of it. I don't recall them making any mention of the undercoating.
My area dry ice isn't something you can just pick up anywhere so I used the HF electric cutting tool and that worked well.

[Tremelune]

A heat gun and any scraper will make quick work of the sound deadening. The tough bit is the carpet glue. It's pretty awful. Plenty of threads on it (most involving CitrisStrip), all involving labor.

[drcoastline]

Originally Posted by Tremelune

A heat gun and any scraper will make quick work of the sound deadening. The tough bit is the carpet glue. It's pretty awful. Plenty of threads on it (most involving CitrisStrip), all involving labor.

^^^ Agreed. A heat gun to warm the deadener just enough to make it pliable like taffy. Don't melt it. Once an edge of the deadener is lifted heat between the deadener and the floor pan it will come out in sheets.

[hcoles]

I've been observing the noise levels in the P-car 89 3.2 coupe and 06 Tahoe (both are parts getters for the other). What I'm hearing is very large changes in noise levels depending on the road surface at highway speeds. E.g. say there is a newly paved section (quiet relatively smooth) and the new paving section stops and I hit the "old" rough section, the noise level increases dramatically. This tells me that the noise at highway speed is largely coming from the tires not the engine/trans. So the question is - where/what is used to most efficiently reduce the tire/road generated noise?

[Mick_D]

New tires.

[enzoducoing]

Hello
I did not know how Dynamat worked when I did my first car and I ended up lining every inch of the interior with the stuff. It did reduce vibration noise and most of the chassis drone, but it was unable to reduce most of the outside sound, and it did add considerable weight. After reading to many posts regarding sound absorption, I decided to do a three layer approach in my second car using Dynamat, Dinaliner and Dynapad. I started with Dynamat only in the recessed portions of the sheet metal, then Dynaliner on the roof, doors, and on top of the Dynamat. To this I added two pieces of Dynapad on the floors under the rug. This definitely brought down the noise to almost contemporary car level. It's still very heavy but not as much as the complete Dynamat solution. Dynaliner is a very light two layer foam material. Dynapad its a very heavy three layer foam material of three different densities.
Hope this helps.
Cheers
MD

[Tremelune]

@hcoles The wheel wells and the floors.

[ossiblue]

Originally Posted by hcoles

I've been observing the noise levels in the P-car 89 3.2 coupe and 06 Tahoe (both are parts getters for the other). What I'm hearing is very large changes in noise levels depending on the road surface at highway speeds. E.g. say there is a newly paved section (quiet relatively smooth) and the new paving section stops and I hit the "old" rough section, the noise level increases dramatically. This tells me that the noise at highway speed is largely coming from the tires not the engine/trans. So the question is - where/what is used to most efficiently reduce the tire/road generated noise?

Read the following post. Dynamat is not meant to reduce outside road noise, only to dampen the noise from sheet metal vibrations. Road noise reduction requires a sound absorbing material like open-cell foam. Your carpet, alone, does a minimal job but does help. Adding absorbing materials under the carpet and behind the side panels (attached to the back of the panels, not the metal skin of the car, and between the vapor barrier and door card) will reduce road/outside noise considerably.

Originally Posted by enzoducoing

Hello
I did not know how Dynamat worked when I did my first car and I ended up lining every inch of the interior with the stuff. It did reduce vibration noise and most of the chassis drone, but it was unable to reduce most of the outside sound, and it did add considerable weight. After reading to many posts regarding sound absorption, I decided to do a three layer approach in my second car using Dynamat, Dinaliner and Dynapad. I started with Dynamat only in the recessed portions of the sheet metal, then Dynaliner on the roof, doors, and on top of the Dynamat. To this I added two pieces of Dynapad on the floors under the rug. This definitely brought down the noise to almost contemporary car level. It's still very heavy but not as much as the complete Dynamat solution. Dynaliner is a very light two layer foam material. Dynapad its a very heavy three layer foam material of three different densities.
Hope this helps.
Cheers
MD

[hcoles]

Originally Posted by ossiblue

Read the following post. Dynamat is not meant to reduce outside road noise, only to dampen the noise from sheet metal vibrations. Road noise reduction requires a sound absorbing material like open-cell foam. Your carpet, alone, does a minimal job but does help. Adding absorbing materials under the carpet and behind the side panels (attached to the back of the panels, not the metal skin of the car, and between the vapor barrier and door card) will reduce road/outside noise considerably.

Good point - the noise generated by the tires on the road can go "outside" and try to get in via the doors/windows/etc. I don't know how much that (outside noise long path) is compared to the noise coming off the tires and coming in directly (short path) via noise vibration of the wheel wells/floor pan/etc. I was referring to the noise coming in via the wheel wells/etc. Good points re. damping noise coming in via the outside long path.

Thanks.

[aread]

While we address the rust issue, I have been researching, going back and forth of what level of sound deadening I want to take this, while still keeping the weight in check.

Once I've prepped the surface from the old sound deadening and have the new pan primed and paint my plan is to follow nineballs method of a 40-50% coverage of a butyl based Dynamat. But then I am torn as to whether to follow it with some mass-load-vinyl or closed cell foam, to reduce the engine and road noise, before laying carpet.

But side note: Here's a photo I snapped yesterday while checking up on the progress. Rusty pan out, new pan on its way in!

[KNS]

Originally Posted by hcoles

I've been observing the noise levels in the P-car 89 3.2 coupe and 06 Tahoe (both are parts getters for the other). What I'm hearing is very large changes in noise levels depending on the road surface at highway speeds. E.g. say there is a newly paved section (quiet relatively smooth) and the new paving section stops and I hit the "old" rough section, the noise level increases dramatically. This tells me that the noise at highway speed is largely coming from the tires not the engine/trans. So the question is - where/what is used to most efficiently reduce the tire/road generated noise?

In my '84 I laid down on the floors 1/4" closed cell foam (CCF) backed with 1/8" mass loaded vinyl (MLV). I did not scrape up the old factory sound deadening, I then put the regular carpet back over the top. It made a noticable reduction in road noise.

The engine and trans do make a lot of noise (not just exhaust noise) that make it's way into the cabin. I noticed new engine mounts made a reduction in noise as well (standard, Genuine Porsche mounts because the standard aftermarket ones failed after a couple of years).