My idea for a cold air intake without cutting into the hood is as follows:
1. Remove Battery and remount it into the trunk.
2. Fabricate an airtight plexiglass air box from the 3/8 in or 1/2 in plexiglass if you can find it that will fit into the space. I suppose an adequate volume would be about 1.25 to 2 cubic feet or so...two would probably be way too big for the space...but lets keep going.
3. Allow access from the top of the box using a sealable lid and secure latch and hinge.
4. Mount the largest K&N open air style filter in the box...I think about an 8 to 12 inch cone style would be plenty. Use a conical or cyllindrical...it doesn't matter. The most important thing would be the inner diameter of the filter outlet. It would need to be large enough in diameter to flow enough air to supply the engine at WOT without restriction, but not so large as to kill intake velocity. I am thinking like 3.75 to 4 inch.
5. Through the bottom of the box, cut two 3.75 in or so diameter holes and run flex tube (similar to the tubing used to route cold air to brakes in racecars) to a NACA style flush mount bumper vent (looks like an A/C vent opening for your house only its plastic behind the lower grill, right next to your oil cooler. Removing the black plastic trim piece that is present in the grill area beside the fog light would be necessary to open up air to the bumper section to which I am referring.
6. (Optional)coat the air box exterior with some sort of heat reflective material.
Now it gets Tricky:
7. Mount a 4 in intermediate pipe to the filter inside the box...you will need to put a silicone coupling on the outer side of the box on the pipe to seal the pipe and keep the filter from moving.
8. Behind the intermediate pipe (which is running towards the strut tower) Mount a Pro M 75 mm or simialar MAF that is correctly calibrated for your injectors. Mounting it here instead of right behind the filter will allow the air flow to have increased in velocity a little bit and, more importanty, allowed the air flow to smooth out into one direction for accurate reading.
9. Using mandrel bent pipe, build the elbow that is to turn the angle from the box to the Throttle body. The bend may not be a full 90 degrees, so a couple of different mandrely sections may be necessary. You would probably be fine with buying a J section and a U section. 3 inch exhaust piping can be ordered from summit, or perhaps you could even go larger. I would build it in sections, tied together with silicone couplings for easy removal.
10. After the bend, place a step down transition pipe that will decrease the diameter of the pipe to match the diameter of your chosen TB as closely as possible. This pipe would be similar to Aussie's Aussie Pipe, and would contain the necessary nipples for the relevant vacuum lines.
11. (optional) Have the entire pipe section Jet Hot Coated or perhaps wraped in hi temp exhaust wrap to cut down on heat soak.
There you have it. A real idea for a cold air intake that wouldn't starve itself for air, would provide decent protection from heat soak, would prevent rain from entering the intake (unless you hit a really deep puddle...then it could be hydo-lock time) and could even build up very modest air pressure levels during high speeds (ram air) You would want to mount the filter as high in the box as possible to prevent water intake should water actually pass up the vent and through the tubes....the theory being that the car would choke down before water is sucked in.
I have been asking for help from different local shops to help me, but no luck so far. Maybe its something my Atlanta contour buddies can help me with one weekend.
