Which one first: "Smart" hot air intake or active grill shutters?

[NoD~]

I recently bought an Arduino and have a few projects in mind. Out of these two, which would you say would be the better MPG starter for me?

-Smart intake system: Create a new filter intake system with two intake openings. One will be smaller and piped to the exhaust manifold and the other piped to cool air. Have a door on an arm that covers one or none. Use Arduino to monitor temps and have control an actuator that closes the door over one of the intake openings based on filter box temps. Have system shut hot air intake upon WOT when power is needed.

-Active Grill Shutters: Arduino will monitor lower radiator temperatures. When the temps get too hot, it will open an actuator to open the grill shutters, bringing in the cool air. Use a simple spring loaded mechanism for keeping them shut and maximizing aerodynamics.

Both projects are pretty close in complexity and time/materials. Both will be done ultimately, but curious which one you think would be the better of the two to start with to gain the most in MPG!

(This is for my Dodge Neon, if you are wondering. Much of the grill is already blocked. The intake is open between the lower opening to the road and the engine, see's mostly ambient temps)

[oil pan 4]

You could use engine vacuum againt spring tension to keep the WAI active when idle and cruise.
Then when you floor it and manifold vacuum drops set it up so that the door switches under those conditions. A fresh air/cabin air vent selector accuator would work for this.

If you drive mostly highway miles I think the grill block will produce more result.

[Piwoslaw]

I'd start with the grille block, more potential there.
Have you seen Daox's thread?
Arduino controlled automatically actuated grill block

[t vago]

I'd work on the WAI. The Neon grille opening is indeed not very large.

[Miller88]

If you can shut the grille off, your stock air intake is most likely going to be a WAI. There isn't going to be any cool air getting into the engine bay (or a lot less), so you'll be sucking in warmer air.