i've thought about it, talked about it, but i though it was time i actually started building the thing, so here we go
the plan is to have a shutter for the top and bottom grille that are moved with a central locking motor and that will open and shut when the fan comes on and off.
i might leave a very small portion of the grill open to ensure enough cooling.
i ordered the motor of ebay for around €6 including shipping, it's a two wire motor and switching the direction of the curent will change the direction of the piston. it has about 1.5cm of travel, testing it on the car battery showed it has quite some power so i think it'll work pretty well
after some test fitting i found the best place to put is was horizontally at the top of the radiator frame.
this however meant i had to come up with somethign to change the direction of the piston motion from horizontal to vertical.
i made some drawings in inkscape (a free vector drawing program) so i could simulate the motion of the components. the setup is pretty simple but it was a little fiddly to get togeter and make sure everything aligned and ran smooth. one handy thing i found was locking nuts wich have a small rubber washer at the end that will prevent them from comming loose over time.
behind the upper grill there wasn't much usefull to attach anything to and the whole shape was slightly curved so i made an insert for the shutters to attach to from coroplast. i'll reinforce this with a few aluminum braces to prevent warping, the pivot points are aluminum as well,this should allow me to install the everything as a complete unit.
next i'll have to make the shutters, i'm currently in doubt between coroplast or aluminum and than i'll have to rig up the electronics.