Wrapping stock intake with tinfoil bubble and then heat resistant wrap?

I don't think I've written about the intake specifically but you can find a bunch of other posts on aerodynamic testing at the blog in my signature. I've been posting intermittently while I finish up a degree in aerospace engineering but plan to be more consistent once I have more free time in the spring.

I believe the duct I used was this one.

 

You say that the coolant is not the source of heat in the engine bay, it's the heat of the engine heating the air in the engine bay.

Guess what cools the engine? Yep, the engine coolant... lower engine coolant temperature will equal lower engine temperatures. Lower engine temperatures will result in lower coolant temperatures. Get a thermostat that opens at a lower temperature, or remove the thermostat like everyone has been saying.

If you want to wrap stuff, you might want to wrap the header and exhaust tubing in the engine bay, and also the larger radiator hoses. They all radiate more heat into the engine bay than the heat that gets picked up from the intake tubing.

SM-S936U ?

 

At the same time, the coolant loop accomplishes that mostly by exchanging that heat ... via the radiator ... into the air flowing into ... the engine bay.

So the coolant ... while cooling the engine ... also is a major source of the heat ... in the air in the engine bay.

I'm not sure what any of that means for the OP's interests, mainly because I'm still not sure I could coherently explain the OP's interests.