Header Ceramic Coating

Last coating company I talked to, can't remember who, said their coating reduced heat by 400 degrees. I'd ask those questions to the coating companies.

 

I bought a header last year for the Ecotec engine on my Morgan. The manufacturer said something similar to me about heat reduction, so despite being somewhat skeptical I ordered it with the ceramic coating. I installed it on the car and went through the recommended heat cycling process to cure the coating. The radiated heat was so intense it would've scorched the paint on the hood in no time. I ended up adapting the heat shield from the OE exhaust manifold as well as applying reflective heat shield material to areas of the engine compartment. Problem solved.
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Have you considered blankets? I have a set of Capristio blankets over my FabSpeed headers. They have reduced the heat felt in the passenger compartment greatly and can be removed for header inspection without having to remove the header.

 

The color of the coating makes a big difference. Silver is cooler that black. I have seen dyno test that have 400 degree + differences in coated vs. painted. Silver ceramic is best for heat.
Black ceramic is better than black paint. I have had them coated on the inside and have not had a failure. It was a race car that sees frequent removal and inspection, not sure if I would put it on the inside of a street car.

 

White is the worst.

 

Color likely makes little difference. Visible light is only a tiny portion of the electromagnetic spectrum.

As a retired heat transfer analyst, I can tell you color only affects radiation effects, emissivity to be specific. Our references made little or no differentiation between different colors. Most paints have emissivities (Fe) in the 0.9 range.

There are multiple processes at work in transferring heat from a moving exhaust stream to the local engine compartment air. From inside to outside the header:

1. exhaust gas to inner wall of header : forced convection and radiation paths in parallel
2. if ceramic coated inside header: conduction thru a relatively thin, but effective, insulator
3. conduction through (stainless) steel header tube wall
4. if ceramic coated on outside of header: conduction thru a relatively thin but effective insulator
5. outer wall of ceramic coated header to engine bay air: free convection and radiation in parallel paths

The total heat transfer path thermal resistance is the sum of the 5-component thermal resistances listed above. It works exactly like an electrical resistance analogy, except a driving voltage is replaced with a temperature differential. Unlike a simple electrical resistance, radiation is a 4th order absolute temperature term. The other terms are linear.

Heat transferred is equivalent to an electrical current. Once the total heat transfer or current is known, temperature or voltage steps along the path, can be calculated.

I hope this helps.

Bill

 

Seems you assumed that the ceramic reduction was equivalent to the stock heat shield.

 

First you say color but all your observations are ceramic vs. paint.

 

The only thing I assumed going in was that the reduction quoted by the mfr. (350-400F) would obviate the need for a shield. I was wrong, and refitting the old heat shield was the remedy.

 

Todd, I think you may have misread or misinterpreted what Wade said. I understood him to mean that silver ceramic was better than black ceramic, and black ceramic was better than black paint.

p.s. Anyone tried Zircotec yet?

 

Well I just dropped off a set of Tubi headers for a Boxer and the professionals told me silver ceramic is the best. I mentioned black and they vetoed that idea pretty quick. Silver isn’t my first color choice but performance trumps color.

 

Thanks Bill. You are spot on and I didn't want to dig into this one because there are so many marginally informed opinions. As for color, in F1 they use white because even tiny amounts of heat are their enemy but in general use it has little impact.

 

In your capacity as heat transfer analyst, you must have some idea of the maximum heat reduction we can expect. Would you be kind enough to share your thoughts on the subject with us? Thanks in advance.

 

Black is the Coolest color for an Overheating Engine

If color doesn't make a difference then can you explain why these guys and others on the web believe that black radiates heat better than other colors?

Excerpt from the URL above.

Black radiates heat in the infra-red spectrum better than other colors, which tend to "specialize" by radiating less efficiently in the infra-red and more in just their color portion of the spectrum

 

Hi Ron

What year is your SE? Mine is a 1966, RHD S2 SE. I'm about ready to start a Jay Leno like, 26R clone.

If I was still in the aerospace industry, I would recommend that we do a controlled test to see what could be learned, because there are many variables and unknowns.

The biggest issue is how to get a handle on the air flow through the engine compartment. Some areas would be affected a lot more than others.

What's really important? To me, the most important thing is the temperature of the air entering the engine. But, in the case of the 308, outside air is routed to the intake, so local engine bay air is not a big concern from a performance standpoint. Still, lower temperatures in the engine bay, are generally a good thing, unless it's 20F below zero.

If I had to run the numbers and didn't have a finite difference (SINDA) or finite element (ANSAS) program to help, which I don't, the best I could do is look at the difference in external, exhaust manifold, surface temperature, under steady state conditions. This might be enough to be useful. If I could show that ceramic coating of the inside and outside surfaces dropped the external surface temperature of a portion of pipe by say 300F,for a given condition, is this useful information? What would not be possible is to quantify the drop in engine bay temperature do to the coating of the manifold.

Simple questions don't always have simple answers.

Bill

 

Hi suicidedoors 1964.

It's not clear who the author is, but I'm quite sure he's not a heat transfer type. It appears he is confusing a black body, with the color black. The terms are quite different in the heat transfer world. A black body is a perfect emitter, which is the same as a perfect absorber. The color black only affects energy in the visible spectrum. I'm not saying color means nothing, it could account for a degree or two, only that is not a design driver and with 30 years in the field, I never once took color into consideration. Surface finish, yes. My experience was the packaging of electronics for commercial and military aircraft (mostly) engine mounted controls (F15, F16, F22, F35, 747, 777, A380, various choppers, etc.,).

 

Any reason why most radiators are painted black?

 

Hi again suicidedoors1964.

You ask a good question.

It looks nice? People think black works better than silver? Lots of folks have had high school physics and equate the color black with a black body, which is probably impossible to actually achieve. Also radiation heat transfer also depends on view factor and emissivity of both bodies, both the emitter and receiver.

If the fins and tubes of a an aluminum or copper radiator are not painted, the surfaces will corrode. The corrosion is actually pretty good from a radiation point of view, but adds an insulator film to the surface. Radiator is actually a misnomer from my prospective. Heat exchanger is a better description IMHO. At low temperatures and temperature differentials, convection is the dominant heat transfer process. At high temperatures and large differentials, radiation heat transfer becomes more important, like on an exhaust manifold. This is because, radiation is dependent on the difference (delta) in the 4th power of the absolute temperatures. Absolute temperature to the forth power of one body surface, minus the absolute temperature to the forth power of the second body surface, if you will.

Radiation is not very important to a automotive radiator. Most of the fin surface area faces itself. If there is no temperature difference between fins and they are facing each other, there is really no heat transfer by this mechanism. Radiators really work by the flow of ambient air over the finned surfaces. This is primarily a convection process.

I hope this helps.

Bill

 

really interesting and many thanks for taking the time to post.

my unscientific view is that my 355 spider runs much cooler in the engine bay with fabspeed ceramic coated (white colour) headers than stock with the heat shields. i live in hong kong and the ambient air is rather warm so every little bit helps

 

Hi DM18.

You might be right, but without a good analysis or test data, it's just an opinion.

As far as running engine temperature, this is controlled for the most part by the thermostat. It's only when the thermostat is fully open and running at the capacity of the cooling system, that differences due to header temperature might be measured.

Bill

 

I had a vintage race car with silver coated headers inside and out by Jet-Hot. The difference was amazing! It always looked like new, even after many track miles.

 

The Zircotec "Performance White" or Swaintech "White Lightning" are plasma sprayed zirconia and go on much thicker than the chrome/aluminum looking ceramic metallic paints that are more of an esthetic type coating.

[ame]http://www.youtube.com/watch?v=MDazh7f1Q_o[/ame]

 

Yep, am aware of the specs. Just looking for any feedback from someone here who's used it.

 

I put white lightning on my headers, but didn't do a controlled test. I did however measure stock, compared to after the coated headers were added and posted my findings in the 360/430 section awhile back. I since added a couple of naca ducts on the rear in addition to the stock ones, to try to increase airflow through the compartment, with one right near the alternator.