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Old 09-05-2012, 11:02 AM   #1
JarHarms
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Info Nugget covering the possible options for thermal control used on exhaust components. Just documenting in case someone needs some info. I have always looked for something that could generally go over these options. As far as I know I could not find one except a bunch of fragmented info here and there.
So I have been sitting on this awhile trying to find a good home for it. It’s definitely technical in nature but would apply to both 2.0L and 2.5L. Screw it, I have a 2.5L so that is where I am placing it.

We are all interested in making improvements or quickly mitigating problems. Controlling exhaust heat is good example since it can affect engine power, engine bay temps, nearby components, material lifespan, etc.
Generalized list of some common thermal control products (in a sort-of order but not really specific)

1)High Temperature Paints – Usually a low cost DIY application of 0.0015” to 0.002” applied thickness. Components may take longer to complete since they require prep and oven/operation curing. Offers some degree of corrosion protection and multiple color choices are available. Honestly high temp paints do not offer any thermal capacity other than lasting slightly longer than a non-high temp paint. These just serve as a a starting point or rather the "low" point.
Failure modes typically include: improper application, flaking off, burning off, discoloration, etc.


2)Thermal Coatings – These cost higher than your average high temp paint and have varied degrees of ceramic content. I tend to think of these in two separate types "nano ceramic based coatings" and "plasma based barrier coatings". Components may take longer to complete since they require prep and oven curing with some prior experience. Offers some degree of corrosion protection.

Nano ceramic based thermal coatings – usually coating service, DIY application possible, 0.002” applied thickness, oven cured, multiple color choices
Failure modes typically include: improper application, flaking off, burning off, discoloration, etc.


Plasma based thermal barrier coatings – coating service, 0.012” applied thickness, application cured, any color you want as long as it is white, can be over-coated with a high temp paint of any color.
Failure modes typically include: improper application, flaking off, cracking, drop out (pebbling), discoloration, etc.


3)Thermal Wraps – Wraps are wraps are wraps. Wraps are usually mild cost DIY applications. Components can be completed quickly once getting used to the wrapping process. Wraps do not offer any corrosion protection without under-coating and even then it is minimal protection. There are differences in physical size and roll length offered by retailers. I have seen thicknesses in the 1/16” to 1/8” range. Essentially there are two material types which I suspect are manufactured at only a few plants and re-branded numerous times. Usually wraps are white or darker graphite color but use of over-coating paints can allow you various color options. The newest release in exhaust wraps is the Lava Rock (LR) type which has significant advantages over the fiberglass versions. The other main drawback of thermal wraps is their short lifespan. Fiberglass type wraps usually do not last long and require reapplication. I am not yet sure of the lifespan of the Lava Rock type wraps, possibly improved? Wrapping can be overdone, most recommend no more than 1/4" overlap and in some cases 1/2" overlap for motorsport use. The limitation on overlap is to reduce overtemp that can lead to substrate damage and weld failures. To me "motorsport use" means competition use where part longevity is mearly a single season or even a single race...hardly a daily (or weekend) driver. Those fancy metal bands are nice but only when you are working with decent sized tubing. Anything smaller and these bands do not remain locked. I prefer to use Stainless Steel safety wire applied with a pair of safety wire pliers. Much faster and more effective.
Failure modes typically include: improper application, clamps/wire breaking, wrap fraying, wrap combustion after absorbing fuels/oils, improper corrosion protection, etc.

Fiberglass Thermal Wraps – 1200 degF direct, 2000 degF intermittent, less pliable, pre-wetting recommended to aid installation, over-coating recommended, itchy as all heck, comes in natural (tan) and black.



Lava Rock Thermal Wraps – 1800 degF direct, 2500 degF intermittent, out-of-the-box pliable so pre-wetting not required/recommended, over-coating not required/recommended, significantly less itchy.


4)Heat Shields – Usually OEM equipped but there are some aftermarket and DIY materials available. There are many materials and mounting methods so the examples as well as cost could vary considerably. I'm going to lump solid formed shields and thermal fabric shields together in this category. These tend to behave similarly and are applied in comparable methods. There are some high tech shielding materials available but at a equally high cost. Shields do not offer any corrosion protection without under-coating. Depending on design a heat shield may be transferable to other parts while the paint, coatings, and wrap won't support re-use or re-sale.
Failure modes typically include: improper application, corrosion, contact with surrounding components, rattles, etc.






Typically application costs run from (lower cost) high temp paint -> thermal wraps -> nano thermal coatings -> inexpensive shields -> plasma thermal barriers -> high performance shields (higher cost).


In the end, proper application of thermal controlling products can provide useful gains. It is up to the user to fully understand the materials or consult with someone who can make knowledgeable recommendations. I am using a combination of parts used by myself, phone calls, conversations, and web research to collect this information. If there are any discrepancies please PM me but be prepared to provide supporting data.


**Yea I know that these photos are all Subaru related parts but I wanted similar looking photos for comparisons. Had to go with Google image search.**
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Last edited by JarHarms; 05-28-2013 at 09:49 PM.
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Old 09-05-2012, 11:02 AM   #2
JarHarms
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reserved for failure mode examples

Flaking thermal barrier. Not sure about this particualr case but I have seen this commonly occur due to poor coating prep and application. Have also seen this happen when a thermal barrier coated part is over wrapped with a thermal fiber blanket then operated at extreme temps. The thermal barrier coating cannot keep up with the expanding substrate and thus fails (cracks). Huh I wonder where those fiber remnants came from, maybe a turbine blanket?


Thermal barrier dropout or sometimes called "pebbling". I have only seen this twice and have yet to get a good (logical) explanation of why it occurs.



Thermal wrap with signs of corrosion underneath. This wrap was causing intergranular corrosion due to holding in high heat then exposing the substrate to moisture post heat cycle. If this part was mild steel or a lesser grade of stainless steel it would show much worse effects.

Last edited by JarHarms; 05-28-2013 at 09:37 PM.
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Old 09-05-2012, 11:03 AM   #3
JarHarms
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What about combining some of the above methods?
Some combination may provide improved results, some may offer no improvement, and others could actually cause problems.
1)Over-wrapping a coated component – This may seem like a worthwhile endeavor but is typically not recommended. Over-wrapping thermal coatings is a fine line between increasing barrier effectiveness and overheating the base material. Overheating the base material can cause expansion which the thermal coating may not be able to match. The result could cause crack development in the thermal coating. There are many factors to consider such as material properties, operating temperature, specific thermal coatings used, etc. In most cases it may be a trial and error learning curve.
2)Adding a heat shield to a coated or wrapped component - This can yield additional improvements as long as there is sufficient space to locate the shielding and you accept the added expense.

Coating component interior surfaces?
This would be the best method only if the application wasn't impractical. I tend to focus on external coatings since I (among others) feel that none of these products are able to properly bond inside most exhaust components. Worrying about the inside is realistically not worth the extensive hassle. Some coatings boast that they can coat the insides of exhaust components, I still have my doubts of their longevity. There are also concerns that upstream interior coatings could flake off and cause damage to turbos and cat-converters. In a perfect world if a decent ceramic thermal barrier could be placed inside and out....I would be pretty excited.

What about other exhaust components such as flex joints and cat-converters?
It is not suggested to use thermal coatings or thermal wraps on either of these types of components. The heat and materials involved do not bode well to the durability of the component or thermal control method used. Flex joints typically "flex" and converters typically have elevated surface temperatures. Usually any type of coating will flake off of flex joints and burn off of converters.

Why bake a coating in the oven when it gets hot during the first use on the car?
Oven cure allows a controlled environment to bring the substrate temp up to the proper cure temp and maximize the coatings' bonding, physical, and thermal properties. In addition to that many cure-on-the-car coatings are hella fragile when dry but have not encountered enough heat cycle. The install alone risks messing up the effort you spent coating those parts. Why cut corners and compromise your end result? I for one hate having to re-do a job.

What evil happens under the wrap?
Usually when steel and stainless steel components are directly wrapped they can exibit an appearance of corrosion after some operation time. This corrosion is more than likely carbide precipitation leading to intergranular corrosion rather than the "corrosion" most of us initially think about. Although corrosion can set in if the wrapped components get wet, do not come to temp, and sit for awhile. High temp exhaust gases can cause material property changes that weaken the metal causing portions of the surface to flake away and appear as corrosion. Using a high temp paint or nano thermal coating could reduce this effect. Certainly do not use a plasma thermal barrier under there due risking overtemp of the substrate.

How about that AeroGel stuff that was suggested in a post?
I was intrigued and looked into those. Besides the high price point I could not find a delivery medium that I would use for some experimental thermal shielding. The tiles were out since I doubt there is much use for rigid mediums. The ThermalWrap looks interesting but the 125 degC temp max is silly. The PyroGel XT (1200 degF) material is dusty (falls apart) but might be usable for some sort of partially formed shield. Same for the SpaceLoft (200 degC) material which is also dusty (falls apart) and isn't going to yield much for exhaust thermal control. If someone wants to try this out and share their results I will add what info you offer up. b3delta?

So what have I used on my past projects? "AKA what the hell do I know"
High temp paints have never met my criteria except for quick and cheap. Wish I had a nickel for every high temp paint job I have had to reapply in short order. As a result I no longer apply high temp paints on exhaust components other than under-coating thermal wrap. Any non-exhaust parts are instead powder coated which has provided me with vastly superior results than paint. And now a day it is not that much more money to have these parts prepped and powder coated.
I have used nano thermal coatings numerous times but tend to reserve their use for appearance and corrosion protection duties. I will occasionally use nano thermal coatings on titanium but will not use any plasma thermal barrier coatings or wraps. Simply too much risk to an expensive base metal.
Plasma thermal barrier coatings are my preferred product for steel and stainless as long as I have the funds and lead time available. However these coatings are troublesome if the exhaust component needs re-welding or modifications later on. These are tough and have to be ground off for a clean working surface.
Thermal wraps also work very well but I will only use them on stainless. I used to avoid thermal wraps altogether due to extra install fiddling, fluid absorption risks, and the itchy fiberglass effect. Since the introduction of the lava rock wraps my experience has improved. Lava rock wrap is a great alternative to thermal coatings when I do not have the funds and wait time. Even though over-coating lava rock wrap is not required I have still done so with a high temp sealing paint. Old habits die hard I suppose.
Looking back I have touched various high temp paints, Eastwood products, Jet-Hot, Tech Line, Performance Coatings, Swaintech, DEI fiberglass wrap, DEI Ti wrap, generic fiberglass wrap, and some sad attempts at heat shields. Have experienced failures with most of these options, honestly most were related to application error or just plain choosing the wrong option. I learned a wealth of information in each catastrophy.

Some threads of note:
NASIOC - Ceramic coating...worth it or no?
NASIOC - jethot or swaintech?
NASIOC - ceramic coating ..plus heat wrap ?

Last edited by JarHarms; 05-28-2013 at 09:46 PM.
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Old 09-05-2012, 01:18 PM   #4
UK-Wagon
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People, Send your stuff to Swain tech..... be done with it.

http://swaintech.com/
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Old 09-05-2012, 02:10 PM   #5
JarHarms
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Quote:
Originally Posted by UK-Wagon View Post
People, Send your stuff to Swain tech..... be done with it.
I also frequently use their barrier coatings with great success. However it alone is not the end all be all for every situation. Hence compiling the info in this thread.

Last edited by JarHarms; 05-28-2013 at 09:40 PM.
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Old 10-24-2012, 06:14 PM   #6
b3delta
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considered aerogel blankets/wraps yet? http://www.buyaerogel.com/ I might try em

What about mixing some coatings up? Thermal dispersant coatings on the intercooler fins, radiator fins, maybe some others. and then barriers on the hot stuff, Intake manifold/TGVs, and sides of the intercooler.

Also, the chimney for the heat shield over the turbo. maybe a barrier coating on it to fight that heat soak and still allow air to flow the heat down and away from the IC

I wanna buy some techline and an airbrush to test some of this out, screw sending it away to some company to do it, all exhaust components cook on the car - no oven needed.

As for the wraps, they are easy to apply, but the metal zip ties they give you to secure itare kind of annoying as a way to hold it down. Also after a year or so of the wrap it is starting to flake and fall apart. Started out black and is now a yellowish white. I am not an advocate for the wrap unless you are willing to swap it out every year. now another thing about the wrap, if u r in a "salt state" (northerners) the wrap is absorbant and may be holding salty water against your pipes which can increase the degradation of the steel, even stainless.

Last edited by b3delta; 10-24-2012 at 06:27 PM.
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Old 10-24-2012, 08:36 PM   #7
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Don't forget turbo blankets (such as PTP).

I'm doing that, plus ceramic coating of the turbo hot side, cobb downpipe, GS cross pipe.
I'm also DEI titanium wrapping the crosspipe since the stock heat shields won't fit, and will paint the wrap with VHT header paint to help avoid oil fire risk.
Also the Cobb heat shield will be ceramic coated.
I won't bother with the ported stock headers, they hold heat fine.

Thermal dispersant on the TMIC (composite TGV also), and turbo cold side.
I might do the rad if / when I get a mishimoto rad (hadn't thought of it)...

I think that's about enough...
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Old 10-24-2012, 08:58 PM   #8
b3delta
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im gonna order some of that aerogel mat and try to rig a turbo blanket out of it. stuff is crazy, can hold a blowtorch to it and the not being burned side is able to be touched with a finger
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