I don't know if any of you watch mighty car mods on YouTube but I saw this video yesterday
I watched it because I had not heard about painting your intercooler black so I just wanted to see what was up.
This is a summary of the video if you don't want to watch it.
Basically the idea is that black objects have better emissivity (I hope that's spelled right) and will transfer heat better but the questions were does it actually work and does adding the paint end up insulating instead or helping. The results ended up being that with air flow to cool the intercooler the black painted one was 3 degrees lower than the non painted one which is worse (not enough to make a difference though) HOWEVER without air flow to cool it from the fan the black painted one had an output temp that was about 40 degrees LOWER! That's good because it means when you're sitting still without air flow to cool the intercooler you can end up heat soaking it which is bad so the 40 degree improvement is great!
So I was thinking that since a radiator and intercooler work similarly to cool either the coolant or air, respectively, if you have a grille block that will allow much less air flow to cool the radiator painting it black could help considerably, especially in city traffic or in a jam on the freeway, to keep the engine from getting too hot. What do you all think?