Firewall sound/heat solution

I have an rx7 car with a totally bare firewall in the engine bay. The turbos are hot and that heat goes right into the firewall and roasts the cabin. What are my best material choices for cutting down on the heat? I was leaning towards fiberglass backed adhesive foil, and covering the entire outside firewall and underside of the transmission tunnel. Probably follow the exhaust routing as well, it's a damned sauna!

What are the other options? Is there a paint-on option I can do with a brush and the engine in the car? Trying to keep it as light as possible with reasonable compromises. Cost is a concern but I'd like to do it right, roofing tar tiles will never come near my cars

This stuff has been popular with the hot rod crowd for a few years now.

https://lizardskin.com

Design Engineering and Thermo Tec should be able to help. We have worked with both on our project cars. 

Good topic, since pulling the carpet from my pickup the heat from the transmission tunnel gets pretty warm especially in the summer. 

I have an FD and Spec Miata. In both cars, I used the DEI floor and tunnel shield under the tranny tunnel and a portion of the firewall nears the downpipe. Works well for heat. Doesn't do much for sound 

DEI floor and tunnel made a significant difference in my V8 Miata with no interior.

I used to have Thermo-Tec Cool-it, but it melted.

We used Lizard Skin in a bunch of builds. I'm not completely convinced. If you're worried about sound, I'd be concentrating on the muffler :)

Anyone used any of the "sheet hot" stuff from vibrant?

https://vibrantperformance.com/catalog/index.php?cPath=1531_1355_1356_1359

Keith Tanner said:

If you're worried about sound, I'd be concentrating on the muffler :)

Lol there isn't a shred of sound deadening anywhere on the car. Sounds are good, but the heat is wearing me out and forcing the A/C to work overtime isn't good for anything

Has anyone used sheets of fiberglass backed gold foil successfully? I'm a sucker for the look, but I can't find any thicker products that have more than a single sheet of fiberglass insulation. Yeah yeah McLaren F1 bla bla I think it looks great (and a 25 year old car should look good)

I would focus on keeping the heat in the turbo to start. Controlling heat from the exhaust under the car next.

A turbo RX7 can also be known as a Car-b-que.

mr2peak said:

Has anyone used sheets of fiberglass backed gold foil successfully? I'm a sucker for the look, but I can't find any thicker products that have more than a single sheet of fiberglass insulation. Yeah yeah McLaren F1 bla bla I think it looks great (and a 25 year old car should look good)

I tried it. I think the Floor and Tunnel is better. Certainly more affordable, and if it comes down to the entire tunnel vs about 2.5 square feet I'm doing the whole tunnel. 

Keith Tanner said:

We used Lizard Skin in a bunch of builds. I'm not completely convinced.

Sorry to hijack, but could you expand on your experience a little? Which Lizard Skin products were used, what were the goals and how effective/ineffective were they? In addition to the hot rodding community, that stuff is becoming very popular in the overlanding/van life crowd too. They use it to deaden sound and keep temps more reasonable in giant tin cans and most seem pretty happy with it. Some of the promotional videos seem pretty neat and I've been considering it for an upcoming project. Most reviews seem pretty positive, but I'd likely value your opinion a little more than a random person with a youtube channel.

racerfink said:

This stuff has been popular with the hot rod crowd for a few years now.

https://lizardskin.com

We've got lizard skin on the Nova.  I have no opinion on the product, since I paid someone to apply it, and the car is yet to run.  Prolly another few months out, maybe longer.

But it was recommended by a reputable restorer of classic cars in my area.  Supposedly has a "ceramic" component that rejects heat along with sound.  Snake oil, lizard skin, I dunno.  Sounds a little sketchy.

jgrewe said:

I would focus on keeping the heat in the turbo to start. Controlling heat from the exhaust under the car next.

A turbo RX7 can also be known as a Car-b-que.

I'm still on stock twins, very little room to add any sort of extra heat shielding down there. Also super hard to check for oil leaks with a blanket stuffed in around them, and an oil soaked blanket is a recipe for a fire. When they come off, I won't be putting them back on, so no ceramic coatings at this point. Firewall will have to do for now

STM317 said:

Keith Tanner said:

We used Lizard Skin in a bunch of builds. I'm not completely convinced.

Sorry to hijack, but could you expand on your experience a little? Which Lizard Skin products were used, what were the goals and how effective/ineffective were they? In addition to the hot rodding community, that stuff is becoming very popular in the overlanding/van life crowd too. They use it to deaden sound and keep temps more reasonable in giant tin cans and most seem pretty happy with it. Some of the promotional videos seem pretty neat and I've been considering it for an upcoming project. Most reviews seem pretty positive, but I'd likely value your opinion a little more than a random person with a youtube channel.

We used both their heat and sound product on a number of V8 builds. It was far easier to apply than patching on Cool-It, so that's a big plus. Note that we were paying to buy it and were not being given free product :)

At some point, we stopped and I'm not sure I ever noticed a difference. That's my biggest complaint.

I think one big reason is that a V8 Miata is going to be loud no matter what magic stuff you slop on the floorboards. I can see how it could damp some vibrations but that's not where the noise comes from in those cars and I think that's probably better handled with a few small squares of a Dynamat-type material.

As for heat, applying it to the inside of the car only means you're trying to prevent a heated chassis from transmitting heat to the occupants. I've had much better luck keeping the heat out of the metal in the first place with Floor and Tunnel and to some extent, Swain. Swain was not as effective as I'd hoped.

My own car has a bare metal interior and had no sound/heat insulation at all. Swain helped, gold was...okay in a small area, Cool-It melted, Floor and Tunnel made a big difference.

mr2peak said:

Keith Tanner said:

If you're worried about sound, I'd be concentrating on the muffler :)

Lol there isn't a shred of sound deadening anywhere on the car. Sounds are good, but the heat is wearing me out and forcing the A/C to work overtime isn't good for anything

Put the carpet and firewall insulation back in?

It doesn't weigh all that much, and as a driver aid it is worth every ounce.

In reply to Keith Tanner :

Thanks! Good point about vehicle type having an impact on the effectiveness. I suppose a fairly modern vehicle with a decently stiff chassis that's had some level of attention paid to NVH from the factory probably benefits less than an older muscle car or  giant cargo van might.

I think the benefit for sound control comes from preventing the large panels from vibrating like a big speaker, which will happen with any vehicle. Big areas will be worse for low frequency, though, so I can certainly see it being most effective in a large coupe or van. Is it better than a square foot of Dynamat in the middle of the panel? That would be a worthwhile test. It sure is a tempting story, though - just hose it on and you're done.

LOL all you guys talking sound. It's a heat issue only. After 1/2 an hour in the car, everything just heat soaks. I can feel it in the chassis, everything is hot.

I'll have to lower the engine to properly cover the firewall and trans tunnel. Might see if I can get some quality fiberglass backed gold foil I can apply without removing everything. DEI trans tunnel looks like I can't really have anything in the way. Not feeling like dropping the engine and trans just for heat reduction at this point, need a few more things on the to-do list before that happens. Then I can use a proper heat shield you guys have recommended.

Never heard of DEI (thought it meant Dale Earnhardt Inc at first glance) but this looks like the product to try..

https://www.designengineering.com/under-hood-thermal-acoustic-lining-32-x-54/

I can imagine the hardest part with panel products is getting a flat sheet to confirm to a surface that is anything but flat. 

mr2peak said:

LOL all you guys talking sound. It's a heat issue only. After 1/2 an hour in the car, everything just heat soaks. I can feel it in the chassis, everything is hot.

I'll have to lower the engine to properly cover the firewall and trans tunnel. Might see if I can get some quality fiberglass backed gold foil I can apply without removing everything. DEI trans tunnel looks like I can't really have anything in the way. Not feeling like dropping the engine and trans just for heat reduction at this point, need a few more things on the to-do list before that happens. Then I can use a proper heat shield you guys have recommended.

Yeah, the post has veered off track. I also see that a lot of people confuse vibration damping, sound absorption and heat control. You need three very different products to combat these three different issues.

I wish I would have thought of heat control on my car. Like you, I don't want to drop the engine/trans to put proper heat shielding on the correct side of the firewall/tunnel/floorboards.

I think the multi-layered, waffled aluminum panels would be the most effective but the most difficult to install.

The aluminum used in these products is not super rigid, you can easily deform it to follow contours. If you have a sharp angle it can't handle, you just make a seam. 

I tiptoed around removing the trans for years and tried a bunch of things for heat management. Ugly, expensive and ineffective. I dropped the drivetrain last  and did it properly and it's so much better. Didn't really take that long, less time than I spent farting around trying to avoid the right solution :)

Pics can be found here: https://grassrootsmotorsports.com/forum/grm/the-targa-miata-moves-to-the-next-stage/176398/page3/

mr2peak said:

LOL all you guys talking sound. It's a heat issue only.

Well, to be fair, the thread title IS "Firewall sound/heat solution"...

I'm also on stock 99 twins. Assuming you already have a downpipe, wrapping the downpipe in header wrap helps. if you have the stock pre cat , remove pronto. 
The DEI stuff can be stuck on the existing heat shielding that's on the tunnel over the exhaust. Just need to clean the surface very well so that it sticks. 
The Por15 degreaser is awesome for this. Spray on and agitate with a nylon brush like those they sell for kitchen cleaning. 
https://por15.com/collections/preparation-products/products/cleaner-degreaser

mr2peak said:

LOL all you guys talking sound. It's a heat issue only. After 1/2 an hour in the car, everything just heat soaks. I can feel it in the chassis, everything is hot.

Sorry for diverting the thread. I figured since you titled your thread "Firewall sound/heat solution", some discussion of sound deadening stuff wasn't off base.