A Better Way to Insulate the Passenger Compartment from Heat

[Les]

I have searched the Superlite forum, and could find no reference to this, so I have decided to put it here. If it should go in a different place, moderators, please, you can move it.

Since the beginning of the SLC, heat has been a problem.

J. Salmon
Join Date: Aug 2005
Location: Lynchburg, VA

Another run at VIR - full critic mode (The SLC) was hot as snot. We kept the car under a tent with both doors open to keep it cooler. . . . One thing to be sure of is that you address the heat. It was a hot day for sure. The SLC windscreen is a work of art (it is my favorite bit on the car). But it also directs all the air away from the windows. So even with them removed, you will not get any fresh air into the car. I don't think you will get any water in either, provided you are moving. You have to stick your hand out the window a good 4-5 inches before you feel any breeze. Plan for some vents.

AIR CON is essential, if you ask me. Just pretend it is a LeMans racer, and realize that it is required. . . .

The engine is behind you. It gets hot. The cooling tubes get hot. This car does not have adequate heat barriers between the firewall or the cooling tubes. In 20 minutes as a passenger my right foot was pretty hot, sitting right next to the cooling tube. The footbox was clearly heating up. The engine heat was also slipping into the central tunnel, and we think this was responsible for heating up the stick shift lever. In 25 minutes it got so hot that you really could not hold it with your bare hand. Again, seal it up really well.

Plan on spending time addressing heat. This is not a new thing, and it is not impossible to tackle. But many cars in history have had too little attention paid to this area and have suffered for it. More on that next post too.. . . Liberal use of thermotec or similar insulation is highly recommended. As is sealing the cabin from all entrance of air from the motor OR the front radiator area. It obviously can work. With AC, a properly built car will be just fine on a 100 degree day for hours.

J. Salmon

Quote:
Originally Posted by CANTDRIVE55 View Post
J,

Thanks for the honest reviews. It's not too surprising however that ther would be a need for some AC and interior heat shielding. Those are certainly add-ons to my things to do list. Heat shielding was an issue I worked on for my Viper as well. I routinely ran the AC in it to prevent brain-fade from overheating. At the least, I will go with some gold foil outside the footwell and on the firewall, maybe more.

Certainly hope this is helping. All of us are spending a lot of time and thought and energy building, and I think it is important to see the bits that need to be done. Otherwise, you put the car together and get in to go for a drive... and you are sweating your butt off cursing.

Quotes edited by me for clarity.

Here is something that will really help us keep our SLC's cool: a material called "Aerogel."

General Motors uses Aerogel to keep the interior of its latest Corvette Sting Ray cool.

10 Awesome Things You Need to Know About the New C7 Corvette

Many owners concur that the center tunnel in the C6 can get toasty, and with the C7 now locating the exhaust in an even tighter space, the potential to exacerbate the problem is very real. To combat this, Chevrolet is using insulation made from Aerogel, a material developed by NASA for use in space suits. Considered for years to be the lightest solid material in existence, Aerogel is 99.8 percent air (thereby replacing the liquid portion of a gel with a gas), yet it insulates 39 times better than the best fiberglass. The C7’s tunnel has a 10-mm (0.4-inch) layer of an automotive grade version of the stuff applied to its sides, and another 5 mm (0.2 inch) on top.

NASA Aerogel Material Present In 2014 Corvette Stingray | GM Authority

The goal is to keep the heat of the transmission tunnel from transferring into the cabin . . .

That's nice for theory, but how does it work it the real world?

Mid-Engine Anatomy - 2014 Chevrolet Corvette Stingray Z51 - Motor Trend

Even after three punishing laps with Corvette racing ace Ron Fellows at the helm, the center tunnel walls stayed cool, thanks to a 10mm layer of Aerogel insulation (5 mm on the top of the tunnel). Used to insulate astronaut space suits, 1 cubic inch of the insulation has the interior surface area of a football field.

Read more: 2014 Chevrolet Corvette Stingray Z51 First Test - Motor Trend

Other component car makers are already using Aerogel to insulate their passenger compartments from heat: The American Ceramic Society | The American Ceramic Society: Ceramic Engineering, Ceramic Materials and Glass Science Resources

Where to get Aerogel? Here is a list! Aerogel suppliers

Don't want to buy Aerogel? Want to make Aerogel yourself? Here! [ame="http://www.youtube.com/watch?v=X24np30GS2o&list=FL5fX7S-zlCydPZw9wKDgrtQ&index=18"]Making silica aerogel at home - YouTube[/ame]

Lighter, thinner, works better than existing materials, already tested by manufacturers and component car makers, what's not to like?

Hope this helps,

Les

 

[Ben Whittle]

It's very brittle though, not sure how they've made it not crack in the C7?

 

[Mesa]

That guy must be local to me, he shops at the same lab supply I do, Lab Pro. My buddy Bob owns the place, he has a Tiger and a Pantera in the back of the shop

 

[Howard Jones]

I think the main plan is avoid radiator exaust air from contact with the foot box. See my build page for how I did the ducting. What is missing there is another small insulator that covers the top of the foot box at the exit of the ducting. This is made of a piece of alum with high temp mat glued to it.

My GT40 is the same animal. Windows don't open and even with the drivers side off the car nearly no airflow INTO the car. BUT if you place a helicopter vent along the leading edge of the side windows at the A pillar they pull in a huge amount of air. Cools the interior to outside ambient in about a lap.

Water pipes will be enclosed with neoprene and shielded from the alum chassis with the same mat material. Firewall has the same mat on it also.

I've run my GT40 on 107F day at Willow Springs . About +110F inside.

 

[Ben Whittle]

Is it safe to ceramic coat (inside and out) water pipes?

 

[wayne]

What ever you do ,do not wrap your coolant pipes with with hushmat.hushmat raised the temp 10 degrees higher than ss pipe.
Howard are you going to glue neoprene to pipes?
Thanks Wayne

 

[Doc Kaler]

Ben,

My intuitive physics would tell me that you might risk raising coolant temperatures overall. For example, the exhaust pipes and engine compartment temps were lower with ceramic headers in my Viper, BUT the heat must go somewhere, ie., out the pipes.....With the closed loop of a coolant system, the higher temp water will recirculate.

 

[Ben Whittle]

Of course, that makes complete sense now you mention it!

 

[Seymour Snerd]

...the heat must go somewhere, ie., out the pipes.....With the closed loop of a coolant system, the higher temp water will recirculate.

But unless the cooling system is already operating at max capacity the thermostat will just open a little wider in order to keep the water at the thermostat's set temperature. So yes the heat has to go somewhere and that's out of the radiator, just like it always does.

 

[Doc Kaler]

Alan,

You are correct in mentioning that, but since the radiator coils have fixed exposure time to the flowing coolant relative to water pump speed I would guess that a new, albeit modest, increase in coolant temperature would be reached in steady state. In practice, not sure if it would be a significant increase though.

 

[Shane]

Just my $.02. In my experience with 18 GTM builds now, you can insulate and insulate all you want, but if the heat has no where else to go, all the insulation is going to do is delay the amount of time it takes for the heat to get into the cockpit. If you're just going to take short trips all the time, then insulation will make a noticeable difference. In the long haul though, I'm guessing you will still end up with a hot cockpit. Instead of focusing on insulation, in my experience, it's much more effective to focus on ways to get that heat OUT of the car all-together....before it has a chance to creep into the cockpit. There is a good reason that first 22 items I have listed on my website focus on heat management and all of them deal with air-flow. If you can find a way to get cool-fresh air into the area that is building up heat, and then vent that hot air back out of the car, then the heat can never build up there to begin with.

The mesh that comes with the GTM kits is very restrictive and flows very little air. If you build the GTM with the solid belly pans and the mesh in all of the body openings, the engine bay gets so hot that you can not keep your hand on the rear hatch glass, and just opening the hatch....the fg can blister your fingers. The tunnel gets extremely hot, the rear "firewall" gets extremely hot as a result. People have ruined their new paint jobs on GTM's when the whole hatch and rear of the body discolors because of the heat. Putting insulation between the body and engine bay to save the paint does not seem like the most effective solution, does it? Wouldn't it be much, much easier and more effective just to push some cool air in and vent the hot air out?

 

[Ricardo Montalvo]

I didn't realize the SLC had a heat management issue with normal (i.e.: no Turbos, or other heat generating mods) builds?

I didn't see this issue with Allan's SLC. He has the basic heat shielding on the firewall, insulated his coolant pipes along rockers, etc but I don't think he went crazy dealing with cockpit heat. Regarding engine bay heat, he did take a page from Lamborghini's book and installed a pair of Spal fans in the rear opening of the hatch to draw out heat similar to what Shane described. I believe he did that to lower his IAT though...not to deal with cockpit heat.

Maybe he'll see this thread and chime in with his experience.

I am also installing fans to extract heat out of the engine bay. But that is more for IAT and because of all of my exhaust area.

Has anyone else had issues abnormal issues with cockpit heat and keeping it cool?

 

[wayne]

Hi,all good points but me point is when you touch ss pipe the ss pipe is 10 degrees cooler than hushmat,also tried hushmat on tunnel where coolant tubes go threw and hushmat is 10 degrees hotter small piece of foam same temp as tunnel.If hushmat is used on fire wall may increase temp

 

[Howard Jones]

Here's the mat I used on the rear bodywork of my Gt40 over the exaust. Still good after 10 years.

https://www.pegasusautoracing.com/productselection.asp?Product=1832

and glue

https://www.pegasusautoracing.com/productdetails.asp?RecID=6854

Roots, no, I just glued the split together, I want to be able to remove it, and tie raped around the whole thing about every foot. Snug not real tight.


I agree completely with the airflow in and out of the car being crucial to cooling. If you don't expel the hot air and replace it with ambiante then the car will continue to heatsoke until something fails. Driver, electronics, power train etc.

Just letting cool air in isn't good enough, there must be a good route out of the car for the hot air, especially radiator, engine radiant heat and oil cooler exaust.

 

[Mike]

If outside air temps are in the mid to upper 90's (heat index 103) the cab was unbearable. I didn't have my a/c working at that time and using this kind of crazy summer heat as an example may not be fair. Since then I have built an air deflector to help move the air up and out the radiator bay and exiting thru the hood rear vent. Not sure yet if the int. cab will be cooler - likely not. Plus I have my a/c running now..... big difference.

pre-deflector: see pic
with air deflector: see pic

It hasn't been that hot lately but it appears, at least, that the engine is running cooler i.e. air thru radiator and out of bay cavity thru hood scoop more efficient.

The roof scoop, I believe, is also channeling hot outside air down thru the interior side roll bar hoop covers. You can place your hand under the corners of the lower dash and it feels like a heater vent. I plan to remove the interior cosmetic roof panel and build some type of conduit to move the air from roof scoop to engine bay without air leakage. This also may help with rain intrusion if I get trapped in a storm.

Regarding the engine bay -- it gets extremely hot. Open the rear engine hatch after driving around and you could fry an egg on the upper horizontal frame rails. Who knows what it's doing to my IAT's. I have wrapped the headers and it has helped some, prior to me getting the exhaust ceramic coated over this winter. I've spent a week looking for venting options on the rear deck lid/window. I found a couple carbon fiber options that I was planning on installing into the back engine window.

The 1st picture shows some mustang hood vents. Mocked some cardboard up and moved around back window.... too large looks goofy (picture). Settled on two naca ducts and they are in transit as I type (see pic).

Didn't want to hijack this thread and make it a engine bay heat thread but they're all related. My main focus is removal of hot air - not it's suppression.

 

[Terry Oxandale]

I'm going for thermal barriers and air movement. The NACA duct will be installed on the under-panel immediately under the front of the coolant tubes running down the middle of the interior. With some air being forced through the tunnel, front-to-back and out the engine compartment, plus ceramic coated SS coolant tubes, and a layer of closed cell foam insulation, I've found that the heat is not noticeably bad, but I don't have an enclosed cockpit either.

 

[Jack]

Mike, take a look at Howard's front clip pics. He extended the opening below the windshield and fabricated a pretty well sealed deflector. I have the race tail and in process of opening up the side scoops, as a few have done to aid in more airflow.
Also looking at rear window vent options. I did make a solid FRP part but have not decided to use it unless I find a workable vent solution. Please post the results with those NACA ducts.

 

[Mike]

How can you go wrong with NACA ducts! So cool, literately! :thumbsup:

 

[Troy Truglio]

What about ducting some air to pass along the side pods and go into the engine bay area. I would think a small duct in the front, maybe 2" could do it, but I am not sure how it would be routed right now. Maybe a NACA duct on the top and/or a small spal fan. The engine bay can use more air anyway so might kill 2 birds here. Even if the air entering the engine bay is a little above ambient here from the hoses it can still be cooler than the million degree temps back there.

 

[Jack]

well, how about a NACA duct on the top wheel arch flat on the rear fenders (leading edge).