[lunarhighway]

i'm working on my own simplified version of this... a single louver will be opened by a 12v motor when the fan kicks in... i've ran a static version of the grillblock at 30°C/ 86F exterior temp... and than the car started to get really hot so i had to take it off.
at 25C/77F engine temps are right where they should be with the block in place.

the only time when i see "normal" people use a grillblock is in winter , so i doubt you can make a car overheat than... but given the proximity to the radiator to the system i think it's got a great defroster behind it, should that be a problem.

what's the biggest hurdle is make something that works reliable enough to trust it to open when your fan kicks in... i'd wire up some led's to monitor the door but for not i haven't been able to build something that's reliable enough