Ceramic acts as a heat barrier, not to keep heat in but rather to keep heat on one side of a coated part from crossing over to the other. In this case we're talking about the upper intake. The upper intake doesn't have "internal" heat like a header primary, it gets hot due to heat soak from the hot air outside of the intake heating the aluminum and that heat passes through to the inside and thus heats up the incoming air charge. It also gets hot from surface to surface contact between it and the lower intake which is in contact with the heads which do have an internal heat source. Also, if the EGR is hooked up some hot air can be introduced inside of the intake as well. Although these need to be concidered, if you can eliminate the heat soak problem it will help greatly in lowering the intake temps.
So... by applying a ceramic coating to the outside of the upper intake you are helping to eliminate one of the three problems. Delete your EGR and run an intake spacer and you delete the other two.
In terms of the lower intake, its probably best to leave it in "as cast" finish since cast aluminum has a greater surface area than polished, and anything you coat it with will hinder the part from radiant cooling. Its going to get hot regardless, so don't do anything to it that'll make it worse. I powdercoated my lower and now I wish I hadn't, I only applied one layer though knowing that it was going to keep more heat in.
So... by applying a ceramic coating to the outside of the upper intake you are helping to eliminate one of the three problems. Delete your EGR and run an intake spacer and you delete the other two.
In terms of the lower intake, its probably best to leave it in "as cast" finish since cast aluminum has a greater surface area than polished, and anything you coat it with will hinder the part from radiant cooling. Its going to get hot regardless, so don't do anything to it that'll make it worse. I powdercoated my lower and now I wish I hadn't, I only applied one layer though knowing that it was going to keep more heat in.
