Heat management, reflective tape, thermal wrap, ceramic coating - EMISSIVITY

[dyezak]

So I keep seeing a lot of people who dump their money into many random heat management techniques with no real understanding of the underlying physics behind heat and managing it.

Emissivity

If you don't immediately know what this word means and the physics implications it has in transmission of heat take a day or two and read up on it. Sit on that info. Then start applying it to under hood heat management.

You will soon realize why JetHot has their patent, why their product works almost 10x better than ANY competing product (i.e. ceramic coating), and why in about 2-3y when their patent runs out the entire industry (i.e. ceramic coating) will swing towards their technology.

You will also see why reflective gold tape works.

You will also see why most ceramic coatings are just for surface protection and don't do much for heat management.

And finally you'll start to conceptualize why thermal wrapping is only good if something was at risk of touching that component...and in general is a bad choice for thermal management.

Just a PSA. I don't have the energy to type up a 10 page explanation of this.

 

[dyezak]

Oh, and if you do understand this. I realize this doesn't cover every situation (i.e. the *need* for a thermal blanket on a top mount turbine housing that will likely touch wires/etc). But it covers most situations and is actually the basis of the factory heat shields too.

 

[cloud9blue]

Agree.

However, the wrapping is still an effective way to reduce engine bay heat. the fiberglass not only as an excellent insulator and reduces the convection of hot air from the bare exhaust pipes, but it also reduces the IR emission from the exhaust as the heat wrap itself just wont get as hot as the metal underneath. It really is as good as it gets unless you are spending big bucks to get custom inconel shielding on your hotparts.

 

[NoQuarter]

Is there an issue with moisture and wraps? Just a vague reference I read once way back.

Something along the lines of wraps holding moisture causing pipes to rust. I suppose if it is actually being driven then hot pipes should take care of that.

 

[fmorelli]

You will also see why reflective gold tape works.
[...snip...]
Just a PSA. I don't have the energy to type up a 10 page explanation of this.

Someone told me that all gold tape is not the same, performance wise, by a long shot. In fact, that the stuff that works is pretty expensive (like what pro car teams use) versus what one may order (say off Summit or Amazon). That the "regular" stuff is pretty ineffective?

Good thread. Thanks.

Filippo

 

[dyezak]

Someone told me that all gold tape is not the same, performance wise, by a long shot. In fact, that the stuff that works is pretty expensive (like what pro car teams use) versus what one may order (say off Summit or Amazon). That the "regular" stuff is pretty ineffective?

Good thread. Thanks.

Filippo

Unless they were talking about the adhesive quality that's not a universal rule of thumb. But like anything...how it is used/installed is just as important as the product itself.

Something that rarely talked about is the fact that emissivity is impacted by the cleanliness of the product. If it gets coated with oil then dirt....all its properties are then gone. This isn't the case with fiberglass thermal wrap. That stuff can get dirty and maintain its same qualities.

 

[R.G.]

Anytime your looking at the tapes make sure to check the temp rating for direct and radiant. Stay away from electrical tape near heat as well. Turns in to goo. There is cheap thermal tape for wiring from 3m that works great.

I use exhaust wrap on my downpipe double wrapped and that ish is awesome. Bossed aluminum works amazing as well if you have some air space. Can buy it cheap off ebay used and get creative if wanting to be extra careful.

I spoke to a commercial coating co that does aircraft, military etc. and the short and sweet of that long convo was the mil thickness of the coating is the most important factor in coatings. Will have to look at Jethot again, was a while back and re sparked my interest in it.

 

[dyezak]

Anytime your looking at the tapes make sure to check the temp rating for direct and radiant. Stay away from electrical tape near heat as well. Turns in to goo. There is cheap thermal tape for wiring from 3m that works great.

I use exhaust wrap on my downpipe double wrapped and that ish is awesome. Bossed aluminum works amazing as well if you have some air space. Can buy it cheap off ebay used and get creative if wanting to be extra careful.

I spoke to a commercial coating co that does aircraft, military etc. and the short and sweet of that long convo was the mil thickness of the coating is the most important factor in coatings. Will have to look at Jethot again, was a while back and re sparked my interest in it.

Yea, I think it's more effective when people educate themselves. But it makes me LOL when someone ceramic coats or jet hot coats a part then wraps it. That eliminates the heat rejection benefit of the coating completely (though it still helps with corrosion resistance).

Anyhow, I just hoped to get some people to think.

 

[The Convert]

Anytime your looking at the tapes make sure to check the temp rating for direct and radiant. Stay away from electrical tape near heat as well. Turns in to goo. There is cheap thermal tape for wiring from 3m that works great.

I use exhaust wrap on my downpipe double wrapped and that ish is awesome. Bossed aluminum works amazing as well if you have some air space. Can buy it cheap off ebay used and get creative if wanting to be extra careful.

I spoke to a commercial coating co that does aircraft, military etc. and the short and sweet of that long convo was the mil thickness of the coating is the most important factor in coatings. Will have to look at Jethot again, was a while back and re sparked my interest in it.

Coating thickness is not the most important, but it does play a role. The composition of the coating is the most important part for heat rejection.

 

[The Convert]

Yea, I think it's more effective when people educate themselves. But it makes me LOL when someone ceramic coats or jet hot coats a part then wraps it. That eliminates the heat rejection benefit of the coating completely (though it still helps with corrosion resistance).

Anyhow, I just hoped to get some people to think.

Ceramics are insulators. It matters not to the ceramic if it is then wrapped or not. It's whole benefit is that it keeps heat from transferring from the exhaust pipe to the engine bay.

 

[Bigdaddyaaron]

I think it is more important to use a solution that is applicable in a specific practice and not just theory.
Jet Hot:
In theory: the jet hot coating will decrease underhood temps while coating the product and insulating heat/reducing emissivity
In practice: (relatively) anything that touches it will melt/burn

Wrap:
In theory: Provides the same/better insulation (not sure on emissivity) as JetHot. Cheaper to apply.
In practice: you can touch this with your bare hand and not think twice, but it is subject to breakdown

physics is important and should be *considered* when making these thermal management decisions, but as we all know from working on our cars, theory doesn't always work out as planned lol. In a perfect world where none of your hot parts are near anything sensitive, a coating like jethot will be fine.

***And lets not pretend like all you n54 bois running gold tape care more about thermal management than looking cool for the gram lmao.