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I need some sound deadening material for the underside of the hood.
Needs to be heat resistant, dull grey or black and self-adhesive.

Saw something in the net that looked OK , but it was in Asia somewhere.
the highly reflective and expensive racing stuff can be found anywhere.

Any ideas

Dynamat works, but it's shiny on the underside

If you use Dynamat, make sure it's Dynamat Extreme

The other stuff isnt heat resistant

Why do you need sound-deadening material for the hood?

Dynamat actually makes a specific "Hoodliner" that costs about $70. See here:

http://www.dynamat.com/

Thanks for the responses.

vrg3--With the removal of the snorkus and the addition of the
fmic there has been an increase in intake noise--as you would
expect.

I've spent years driving modified cars and at one time loud
was good, but not no more.

Quiet is another dimension of having a "sleeper".

I don't think the sleeper part is worth adding that much weight.

Add the dynamat to your firewall, wheelwells, and doors (as well as under all carpeting) instead and you'll have a much nicer interior sound (or lack of). Most people cannot hear your intake and stuff from their car anyways.

Yeh, Dynamat weighs a crapload.

Well---the other part of the exercise was to shield the hood
from the heat of the pipe from the turbo to the I/C. Also
the new stock one is one grade above cardboard, and looks
it. Also it doesn't line the full underside of the hood.

Other than one of Laurel's layer cakes, what's an alternative?

Weight is not good.

There's that basic heatshielding stuff that you could get at home depot and probably spray paint with a vinyl paint or something

+1 for Laurel

The underhood pad isn't really designed to reduce noise. It's fire suppression.

Sound deadening is usually controlled in the cabin, and if you are really concerned with noise, invest sound deadening material where it will make a difference.

It's not going to make much difference on the outside, how much sound deadening you have under the hood. Really fast cars are loud. It's the way the world works.

It will barely be any quieter from the outside, if you install sound deadening material under the hood. It could be a potential fire hazard though.

Years ago I had a 1600 Alfa roadster--took the air box off, and
put velocity stacks on the twin-choke Webers. The
sound was awesome and the thinly insulated hood amplified
the intake roar. , then.

Now I just want to isolate the hissing sound and diminish the heat
transfer to the hood.

you could heat wrap the intake pipes and turbo stuff with that expensive stuff you spoke of. i'm pretty sure it will still be cheaper than dynamatting your whole firewall and under all the carpet. not to mention easire than pulling out all your engine stuff that attaches/goes through the firewall.

Don't mod?

You gotta pay to play, so just remember that. Anything you do to supress the sound of power, will slow you down.

Why is there more heat transfer to the hood? Because the IC pipe runs close to it? Every FMIC kit for the WRX either touches, or almost touches, the hood, and no one has problems with that. I wouldn't even worry about that aspect of it.

Oops--All I need is some stuff to stick to the underside of the hood to
reduce the heat transfer and to reduce the intake noise--neither has
anything to do with performance.

Also, where the turbo to fmic pipe is closest to the hood there is no
insulation at all, and a patch would make it look even worse.

Low frequency noise is reduced better by heavy materials - like dynamat

high frequency noise is reduced better by low density materials like foams. you mentioned hissing so you should really be reaching for some of the adhesive foam that sticks to the underside of the hood

still as vrg3 mentioned, its mostly the sound radiating through the firewall that you hear.

Most of the noise audible from outside the car comes from the exhaust

IMO, muting the hood will do little by itself.

You'd have to do the hood, the fenders, the bumper, and somehow stop sound from coming out the bottom of the engine compartment and bouncing off the road

Prof.

I'm with you --I took a B.Sc. in Geophysics.

There are 2 ways of looking at it. One is to prevent sound from coming in,
by adding to the the insulation already put in the body shell. The other is to
absorb some at the source and at the same time ease the heat to the
hood , as well as getting rid of the OEM garbage liner.

No big deal, and all advice has been appreciated.

I guess I'm just not sure why you are trying to do this?

If you sound deaden the hood, you'll still hear everything just as loud outside the car as well as inside the car. You'll add weight (reducing performance), and the only "benefit" is to get rid of the OEM "garbage" liner (which is for fire suppression, NOT sound deadening).


So I guess use some Dynamat Extreme or whatever to accomplish whatever your actual goal is. I would be almost certain you won't notice any difference, or any difference worth the extra weight you'll add (even though you'll only add 2 pounds at most, it wouldn't be worth it to me).

Two lbs I can handle.

Last year the twgon got about 40 lbs lighter---Got rid or 20 by shedding
the mechanical U S seatbelt BS and went on the Atkins diet.

But you won't gain anything noticeable in the sound suppression department unless your intercooler pipes are rubbing your hood...