So these are on my 97 Miata and I am not so sure they really do any good as far as getting more cool air under the hood. I still have original un-vented lights and will re-install them if these vented units aren't doing anything! Besides, the tiny lights on the vented units are just barely visible and with a car this small I want to be able to be seen when about to make a turn!

 

They are actually counter-productive to cooling.

 

How are these counter to cooling SixShooter? Doesn't having more air "rushing" into the engine compartment keep things a bit cooler and add more air for the engine's intake? I am not doubting what you've said just wondering what you mean.

 

Air "rushing" around the radiator instead of through it does you no good in cooling. The pressure differential between the air in front of the bumper and the air within the engine compartment creates flow through the radiator at road speed. When you allow the air a short cut and therefore increase the pressure within the engine compartment, the radiator will perform less well.

The engine itself is not air cooled and is not designed to be air cooled. If you removed the radiator entirely and simply looped the hoses so the water flowed directly back to the water pump, took the hood off of the car entirely, and drove at highway speed in 40*F weather, the engine would overheat in just a few miles. The primary purpose of the radiator is to present a large surface area for the transfer of heat to the passing air, something the B-series block and head are not designed to do.

The Miata is susceptible to overheating with the simple removal of the stock radiator undertray and bumper mouth ducting to the radiator due to the tendency for the air to circumvent the radiator rather than to proceed through it. This is exacerbated when a turbo or supercharger is added and the amount of fuel burned and heat generated is increased. If there is ever a complaint of overheating on a Miata the first question is, "Do you still have the factory ducting and undertray in place or have they been removed?"

 

Thanks again SixShooter. I have taken the air-breathers out and re-installed the stock light fixtures.