Here are my current thoughts on the coatings from reading a number of posts on the subject on VAF and performance auto applications.
Piston tops / Combustion chamber coatings
Uncoated pistons / Combustion chambers will build a layer of carbon that will prevent heat transfer, which is what the effect these coatings accomplish. It is thought that one of the factors causing new / new rebuilt engines to run hot during break in, is the lack of this carbon heat barrier. During this time the coatings will act as a heat barrier. Also if you clean the piston (additives, physically) this layer of carbon deposits will need to build up again and you are at a higher risk of thermal damage during this time. The coatings do not prevent build up of carbon. I believe that it is a good thing to reduce excess thermal transfer to the heads / valves / pistons during break in, but getting the "greatest coating ever" is not necessary since it will be shortly covered with carbon deposits serving the same purpose. NOTE: If you are going to run LOP, less carbon will build up, this could be a reason why the LOP/ROP discussions occurs, and the stories that LOP destroys engines.
Piston Side Skirts
This reduces friction "scuffing". Get it. It is reported that over time the coating will wear off. My thought is if you get a couple hundred hours of better, lower friction running, you'll have a better chance of reaching TBO.
Exhaust coating
Coating the outside only will cook (melt, embrittle) your pipes. It has been recommended on VAF, that if you coat, you coat the inside or both. Seems like a good idea to keep under cowl temps down.
Heat Emitting Coating
Thick black enamel is an insulator. NASA document 19730058055. Seems to recommend a very thin layer of no more than .002" of black paint will help move about 3% more heat out of the cylinder versus raw metal.
References:
http://x-jets.com/a_cooling_efficiency.html
Nasa document #19730058055
NOTE: This is a derived work. I'm just trying to collect the best info as best I can. Any comments appreciated. Also I reserve the right to be completely wrong.
Piston tops / Combustion chamber coatings
Uncoated pistons / Combustion chambers will build a layer of carbon that will prevent heat transfer, which is what the effect these coatings accomplish. It is thought that one of the factors causing new / new rebuilt engines to run hot during break in, is the lack of this carbon heat barrier. During this time the coatings will act as a heat barrier. Also if you clean the piston (additives, physically) this layer of carbon deposits will need to build up again and you are at a higher risk of thermal damage during this time. The coatings do not prevent build up of carbon. I believe that it is a good thing to reduce excess thermal transfer to the heads / valves / pistons during break in, but getting the "greatest coating ever" is not necessary since it will be shortly covered with carbon deposits serving the same purpose. NOTE: If you are going to run LOP, less carbon will build up, this could be a reason why the LOP/ROP discussions occurs, and the stories that LOP destroys engines.
Piston Side Skirts
This reduces friction "scuffing". Get it. It is reported that over time the coating will wear off. My thought is if you get a couple hundred hours of better, lower friction running, you'll have a better chance of reaching TBO.
Exhaust coating
Coating the outside only will cook (melt, embrittle) your pipes. It has been recommended on VAF, that if you coat, you coat the inside or both. Seems like a good idea to keep under cowl temps down.
Heat Emitting Coating
Thick black enamel is an insulator. NASA document 19730058055. Seems to recommend a very thin layer of no more than .002" of black paint will help move about 3% more heat out of the cylinder versus raw metal.
References:
http://x-jets.com/a_cooling_efficiency.html
Nasa document #19730058055
NOTE: This is a derived work. I'm just trying to collect the best info as best I can. Any comments appreciated. Also I reserve the right to be completely wrong.
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