Movable air dam/grill block for lower air intake

I had problems with grill blocking during the Fall and Spring seasons in Virginia because we experience quick swings from near-summer temperatures to near-winter temperatures. My solution was to construct an air dam with movable panes of Plexiglas in the lower air intake. The panes are mounted in an aluminum picture frame formed to fit the lower air intake. Currently, the movable panes are held in the "open" position (Summer air flow) or "closed" position (Winter grill block) by small bungee cords:

For the Summer position the panes slide behind the relocated front license plate. A front license plate is required in the Commonwealth of Virginia ( and I still have to fill the holes from the old license plate mounting):


For the Winter position the panes slide out to the left and right hand sides of the picture frame assembly and close off the air flow:



Shifting from Summer to Winter positions involves unhooking the bungee cords, sliding the panes, and rehooking the bungee cords, which takes 10-15 seconds and is a lot less hassle than removing the foam grill blocking I used the last two winters.

This solution would work in all USA states that require a license plate as all states have a standard 12-inches wide by 6-inches high dimension for their license plates. A European license plate is wider, but the frame assembly can be built wider to accommodate that change in width and the sliding panels could probably also be commensurately widened. Unfortunately, I do not have a European license plate available to try this approach out and cannot be sure the design is feasible for those plate dimensions.

I am monitoring coolant temps with a Scanguage II, so I will let you all know how this works out in practice in the next few seasons.
Questions?
Comments?
Vague Misgivings?

 

I embedded them in the text, and can see them either from a Windows 7 system with Chrome or my Apple IPad , so not sure how to help, but if you PM me I will try to send them to you directly.

So far the blocking seems effective in expediting a quicker warm-up and does not cause overheating at 55 degrees F outside temperature, although the water temp stabilized at 195 F, which seems to the the thermostats wide open setting, when on the freeway.

 

Thanks for info.
I also will leave the upper grill unblocked as I think that airstream directly impacts the inverter cooling radiator loop and keeping the inverter as cool as possible is one key to a long inverter life.
The ICE is happier running near the 195 F thermostat setting, though, and that's what I am trying to maximize. I'm in Virginia so we have hotter Summers than in Edmonton, and next summer I will see if the cooling system can keep the ICE down at safe temps when the ambient outside temps are in the 90s, which is fairly common here, with the the two roughly 6 inch X 4.5 inch openings when the doors are slid behind the license plate.

 

Thanks!
Good idea and I have the foam left over from last winter's grill blocking, so can do if it stops raining today.
I joined party late and missed this plus probably other good ideas. Anyone have a good schematic diagram of exactly how,the airflow is supposed to pass around the engine transaxle unit and exhaust underneath?
Some piston engine aircraft use cowl flaps to regulate airflow cooling the cylinders so as to minimize drag in a cruise configuration, and I am wondering if a similar approach would work maybe under the engine bay of the Prius? But I surely do not wish to screw up the airflow pattern designed by the Prius engineers and inadvertently make things worse!

 

3-year update on the Original Posting:

Shutters (vents) open:



Shutters closed:



The movable lower grill block has endured very well in practice. When climbing the Allegheny Mountains with the grill block in the “closed” position, I observed ICE water temps,of 200-201 degrees Fahrenheit on the Scangauge and stopped to open the grill blocks before proceeding up the mountain, which did bring the ICE water temp back down to 198 F.

The two pics below show the right and left sliding plastic ‘doors’ in the “grill closed” position, and when opened they slide behind the central license plate. The picture frame sections I used for the framework are aluminum and show no signs of corrosion, but the steel eyelet in the corner that secures the small bungee cords has started to rust a bit. The small bungee cords last about a year when exposed to the weather, so they have been replaced twice.