So Lloyd, what would you recommend using as a coating? In your opinion will the spray can stuff work fine?
A two part thinned Epoxy would be optimal in my opnion. Aluminized would probably be best, as the aluminum particles, will better match the base metal in thermal conductance, and have the lowest thermal resistance. Further, the coating is quite tough for a long lasting durability. I think it important to keep it thin, though. Two part paints are rather inconvenient. If you want a silver engine I suspect this would work well. But, I don't know about the fuel resistance aspect.
http://www.chiefaircraft.com/aircraft/chemicals/paint/ca-wp-silver.htmlAll the paints I have direct experience on engines with are no longer available in California.
However, I would consider this:
http://www.plastikote.com/products/Specialty/Brake-Calliper-Paint.htmlIf you can believe the MFG claims of "500°F coating that is chemical, chip and rust resistant". It seems ideal if you don't want or need flat black.
I would test any paint before committing to the whole engine. But then, I've been lied to by product salesmen many times, both on the job professionally and personally.
FYI: Radiators are painted black for a reason. Black has the best heat emissivity of all colors. So, it adds radiation to the transfer, as well as contact transfer to the air molecules. But, you never see a thick black coating on a factory radiator for a reason, and that is because black paint solids don't necessarily have high thermal conductivity values.
Black also collects heat and passes it to the substrate. Much depends on the temperature state at the instant of scrutiny, as heat energy needs a differential in order to transfer, and the more extreme the differential the faster the transfer in any conducting device. The coating can transfer outward and inward.
If the case has a thermal transfer resistance (it does), any additional resistance, as a path way component, however small, can only add to the resistance path, which diminishes the cooling effect.
If that were always the case, heat sinks would not work.
I don't know what the poster's definition of a heat sink is. But, any junior engineering student would observe that true heat sinks add at least two significantly important properties, mass and increased surface area. Neither of these fundamentals is present in a simple surface coating.
So, my statement IS true in this matter despite the implicit denigration and personal opinion fueled bias.
Further, one of my earlier lessons in applied engineering was, that questioning a design or product is NOT a bad thing as the good ones will withstand and prove themselves and the bad ones based on hype or human desire, will not stand scrutiny and maintain a favorable standing.
Simply slinging mud at the questioner, does not prove a product or design valid. It only obscures a product's or device's real functional integrity.
I did follow the diversion link (clubwrx) that was posted. I couldn't find out how the device was tested, where the measurement points were, what test equipment was used, its accuracy rating, and error component. I found the data to be inconsistent, apparently the dispersion coating worked better at some temperatures than others (I'd like to understand how that can be), and at times there were no differences. The numbers aren't consistent either in actuality or by measurement error. And on top of that, it was a test case of one, which is always inconclusive. So, the link was basically a waste of time. (Though, I'm sure the poster meant well. It's the testing skills that were lacking. It's not easy to set up and perform conclusive tests and experiments. Particularly so, if the training and basic knowledge are scant.)
In short, just like the manufacturers marketing claims, the link reference also has no science or engineering to support it. Any reputable engineering organization would dismiss both, as having no foundation data to stand upon. In any of the companies I worked for, it would have to be tested in house before approval, if the manufacturer could not provide substantive test data.
What remains is that the product recommend (TLTD), still has no test data to support their dubious claims. And, there is no evidence to believe they are the same or perform the same as some other manufacturer's product.
