Replace sound deadner with what...not Dynamat??

[expat]

While I'm in the process of replacing my carpet I also need to replace the sound deadner under the rear seats and transmission hump.

Now, my observation from removing the original deadner is that it also reduces heat (sorry - provides a barrier) in the cabin.

I've read several comments about Dynamat being good for vibration reduction and Dynamat Extreme being better again.

My interest is more in the heat reduction area.

What recommendations do you have to replace my original deadner (which is now completely dead!)?

[banjomike]

I don't know how heavy the original stuff is, but dynamat works well because of two reasons. It is tar-like and so absorbs vibrations pretty well, and it is heavy. The dynamat website says .5lbs/sq ft. for extreme and .7lb/sq for orignal.

Several vendors including PP sell the original pad, already cut to shape and in one piece. This is important since any gaps will significantly reduce the sound damping characteristics. Plus it'll be much easier to install and the factory has already made all of the effectivness vs weight decisions.

Having said that the TacMat material on the dynamat website might work well, but at .25" thick I bet it doesn't work as well.

[k9handler]

um......nothing! Go with the lightweight option, and listen to the music created by the porsche powerplant!

[speeder]

What about the heat created by the Porsche powerplant? That's the real problem, if it's a street car. (Or a track car, come to think of it).

With nothing at all back there I think that a 911 would be unbearable in regular use. The engineers at Porsche weren't idiots, they did not one day simply decide add 50+lbs. of frivolous weight to the rear half of the car.

[banjomike]

What speeder said!

Several people have posted to this board in the past saying that exact thing after removing some or all of the insulation.

[turbo6bar]

expathk, you need something that insulates. I think the Dynamat is more of a deadener. Something that insulates would be carpet padding and foil-backed bubble wrap. Two other materials off the top of my head are ceramic and asbestos. You could not use the asbestos under the car, but possibly under the carpet.

Go to http://www.mcmaster.com and go to page 3226. This page is for heat insulating wraps and blankets. There, you can view the heat flow and weights. Obviously, you want something that is going to be lighter than the stock padding, but still insulates well.

A product I use for insulating air conditioning ducts in homes (patch jobs to fend condensation problems), is Reflectix. http://www.reflectixinc.com I'm not sure how well it would work, but the stuff is relatively cheap to purchase. Coupled with a quality foil tape, it would be much better than carpet over bare metal.

Jurgen

[k9handler]

I have not seen that to be the case...yes it gets warm, but I don't ride in the back. I have had mine out and have has a few small passengers for quick trips around town and none said "It's hot back here". I do have the mat in the engine bay, but nothing other than lightweight carpet and the seat pads with original rear deck. Even after a 2 hour drive on the autobahn, nothing in the back is anything but warm to the touch...but that is everything inside since I don't have AC. Just my .02

[widebody911]

McMaster-Carr has lots of different self-adhesive sound damping products available, and they're a helluva lot cheaper than DynaMat.

http://vintagebus.com/cgi-bin/search.cgi?string=mcmaster-carr

[BGCarrera32]

Eastwood sells some silver waffle sheet heat reduction stuff along the lines of a dynamat type of material...

www.eastwoodcompany.com

For sticking to curves and doing noise reduction, you can't beat Dynamat. Waaaaaaaaaaaaaay overpriced tho IMO, you'd think they lined it with gold...

[Kemo]

What is the pad in the engine compartment for? Heat, sound or both?

[expat]

Just to clarify for anyone who reads this thread in the future...

I removed the interior sound pad, seats and carpet from my 1987 cab. Lost weight for sure.

Kids coundn't ride in the back so I put the seat pads and backs back in. The kids complained how hot it was.

I put my hand on the trans. hump and it was frickin hot - nearly capable of a light burn to bare skin.

I cannot tolerate this and the heat in the cabin must increase. I will take a surface temperature this weekend and post it here but I can tell you categorically it is real hot! So hot that the horse hair stuffing on the seat pads smelt bad after about 1 hr driving. (YEMD)

I am not concerned at all by the noise or vibration (I've got a cab. remember!) but I must reduce the heat problem. Note that my exhaust is a stock unit except for the cat bypass.

Thanks for the leads on some of the products and I'll follow these up.

[turbo6bar]

From Eastwood Company, product numbers 70309 and 70312 look like excellent alternatives, but then you'd have to question the weight vs. the stock stuff. I imagine it's still lighter. You are interested in weight savings, right? Otherwise, get the stock padding.

Jurgen

[expat]

Nup - given up on the weight savings - more to be gained by me losing weight first before the car!

Thanks for the numbers, I'll take a look.

Mark

[Elombard]

I just bought some material for this. It was $20 US for a 6'x9' sheet of material from an auto parts store called PEP Boys here in the states. It is sold as auto under carpet pad/heat/sound insulation and has aluminum type foil on one side. As a bonus it is very light. Nothing like the quality of what they sell at Eastwood I am sure. It looks very similar to the carpet pad that goes under your house shag but with the foil. The density of the "foam" is very light so their should be a good air pocket and with the aluminum it may be an excellent light weight inexpensive solution for yours and my problem. I will report after I get it installed. Some one else on the board actually mentioned it maybe they will chime in with how it works. I think if you search for a thread with the "dynamat" in it we could find his name.

[kellzey]

What about neoprene sheets (like computer mousepad material)?

It's full of air holes and made of rubber so it should absorb some sound. Heat insulation...??? Not sure.

I've thought about getting some 3/8" thick sheets and using that under the carpet on the floorboards and the rear firewall?

[5axis]

right stuff for the job

http://www.thermotec.com/

[911pcars]

The best method of preventing heat from entering an enclosed space is to block the heat source outside of the container, not inside. That means placing some sort of heat insulator on the engine-side of the bulkhead (if that's the source of the heat). Considering engine compartment temperatures of around 150ºF or so, it could get warm inside the car.

I installed some mylar faced foam insulation (about 1" thick) in place of my decayed sound pad some years ago. It doesn't look anywhere close to what the factory provides, but I guess it's effective for what it does. I've been thinking of removing the horsehair lining from the rear to save some weight. I think sound dampening, if anything, is the material to use inside rather than any heat insulation material.

Sherwood Lee
http://members.rennlist.org/911pcars

[Randy Webb]

Virtually any porous material will give a high degree fo insulation to heat flow, and it will all be roughly the same "insulative" value. Different materials will differ in how well they hold up. and in how they perform at very high or very low temeperatures (but this situation is all at pretty moderate temperatures -- < boiling at the bulkhead [you hope], but higher than "room temperature). I would focus on the wt. and durability of the material. Sherwood is correct about stopping the heat before it reaches the bulkhead.
re: The post about somebody's kids getting fried -- we don't know the condition of his sound pad (or of his kids whine threshold either). It would be interesting for people who have done this to give ballpark estimates of whether pulling out the interior rear seat area pads chaned the heat level -- and of course, better if a statistically valid set of folks did this using thermocouples and dataloggers...

[widebody911]

Anything Eastwood sells can be obtained elsewhere for a lot less $$$.

[expat]

Originally posted by Randy Webb

re: The post about somebody's kids getting fried -- we don't know the condition of his sound pad (or of his kids whine threshold either). It would be interesting for people who have done this to give ballpark estimates of whether pulling out the interior rear seat area pads chaned the heat level -- and of course, better if a statistically valid set of folks did this using thermocouples and dataloggers...

It was my kids who complained Randy and I can attest to their 'whine', because I felt it and it was F$%#n hot!

The sound pad was in average condition for a 16 year old car, (a cab. at that), which I think means the pad has been wet several times in the past.

This weekend I will take temp measurements and post them but I haven't got data loggers or thermocouplers so maybe it wont be 'statistically valid'.

The suggestion about creating the barrier fro the outside has great merit. Need to investigate what materials would work there.

Mark