I am bringing this thread back from the dead of 2009.
A quick update. I did install the grill block on my 2003 Matrix. It did not open and close properly because the grill block conformed to the front grill which is curved. When you bend a hinge it doesn't like to work well anymore. It likes to snap open or shut. Being that it was made mostly from coroplast, it just bent and didn't open. I dinked around with it a little, but not enough to get it working properly.
I have long since sold the Matrix and the grill block has been sitting on my shelf since. I think about the project here and there and how I'd go about improving it (aka making it actually work) should I go about having another crack at it. The time has now come for that second crack.
This time around I've changed a few things. Mainly, the grill block must be straight and flat, and it also has to be more rigid. The flexible coroplast "frame" was a major problem. The frame is now made of aluminum angle that is bolted together. This allows everything to hinge properly and easily. Secondly, the thing was a big pain to work on while it was on the car. This new version is designed to be an insert so it can be relatively easily removed from the vehicle to be worked on. The mounting of the actuator was also an issue so it has been moved off of the grill block. It will now be mounted somewhere on the vehicle and it will actuate the grill block via a flexible pushrod. This will make mounting the actuator easier and allow it to get out of the way of water and other things.
On the electrical side of things I've decided to tap right into the coolant temperature sensor. I already have been working on a coolant temperature hack for the Prius, so I already have an arduino in the car and tapped into the coolant temp, so its already half done for me.
So, let me explain what we actually have here. Its an aluminum angle frame. The opening will be 12" wide by 4" tall. My upper grill has less area than that, and I have my lower grill blocked year round, so it should be plenty of area. The shutters are made of coroplast with a 1/8" steel rod stuck through one of the corrugation pockets. This acts as the hinging point and adds some rigidity. The steel rod is bent on the end to make a lever for the actuator to push on. The two steel rods are connected by an aluminum plate with some holes in it. Another bend could be made on the steel rods to capture that plate. Not pictured is a flexible pushrod that will attach to the aluminum plate. This will go to the electric door lock actuator so that it can push the grill block open and closed. An Arduino will be used to interpret coolant temperature and decide when to open and close the grill block. Using an H-bridge allows the Arduino to easily control the door lock actuator.
I'm very happy with the design thus far. It should prove much more robust and really doesn't cost much more at all. The aluminum angle is a couple bucks and the 1/8" rod is also very cheap. Any coroplast can be used and painted to look good even. But, I'm always open to new/other ideas.