The Mazda has a grille opening large enough and placed properly enough to pull in a lot of air through the radiator. They even have an undertray to help facilitate that airflow.
In regular production street cars, the angled footwell portion of the firewall is enough to direct under-hood air out from the engine compartment and out the bottom of the car, but that can begin to fall short of what’s required for racing. That dynamic also can create lift on the front of a car, which is less than desirable, particularly for high-speed cornering where front grip is essential.
One simple solution is the addition of hood vents, which relieve under-hood pressure and also remove heat from the engine bay. That’s true for any car, but we happened to know a guy who needed to do the job on his Miata, so we followed along for the most important part of the job: finding the right place to put them.
As air travels over the hood of a car at speed, it creates areas of low and high pressure. Low-pressure areas are better place for locating the hood vents because they “pull” air out from under the hood through the vent.
On a Miata, the low-pressure areas best suited for removing hot air are pretty well established. You just need to figure out which vents you like, or which are legal for your class, and where to put them.