[lunarhighway]

some carmakers like bmw are using automatic grillblocks that open/close depending on cooling requirements.

for cars where a full or even partly grillblock can cause overheating can be a problem with the grillblock a manual or automatic variable grillblock might be interesting.

using the electric fan signal as a trigger should give you a fairly good indication when things need to open.

cooling can also be improved by using hood vents abouth halfway the length of the hood just ahead of the windshield stagnation bubble. as hot air rises these will even aid cooling when the car is stationary.

than again if a grillblock is not an option, it means the designers did a good job of giving it the right size for the engine and it's as efficient as they could make it.

manually installing a grillblock in winter is also a good practice, cars like the old citroën 2cv used to have a factory supplied, grille sleeve with just a few tiny openings to block the grille in winter, but even a piece of carboard in the coldest days is something.