What are yer current intake temps above ambient? If the goal is horsepower, how much more horsepower will you gain by dropping the air inttake temps close to ambient? Have you measured the actual gains? How much more flow are you looking to increase? Do you have a way to measure it?
You could build a dedicated ram system off the nose and straight line the tunnel through the passenger compartment to the engine bay.
The best I ever got my intake temps was just a mere 4 degrees above ambient (measured with OBDII on the air intake temp sensor) using a ram air setup off the lower air dam. Horsepower wasn't measured before or after. Chances of sucking in water into the intake system was greatly increased if I were to drive on any flooded street. I ran with this setup fer over a year and decided it wasn't worth the risk...so I returned my air intake back to stock which pulls air from the front fender. Air intake temps are only 10 degrees above ambient from this location...so a mere 6 degrees difference while at traveling speed. Would 6 degrees make a significant difference to yer goal?
I'd be curious to find out how much of a measurable difference a properly designed NACA air duct would make fer yer application.
http://en.m.wikipedia.org/wiki/NACA_duct
http://www.formula1-dictionary.net/naca_duct.html
Quote:
A few words on implementing your own NACA duct as a means of induction to your race car.
-1: design is very important. The duct is designed to be efficient with the correct wall angles (sharp), base slope, and width-to-depth ratio.
-2: The duct needs to be installed in an area of high pressure. A leading edge of a car is a great place.
-3: Don't buy garbage. Edges on the slopes have to be sharp, otherwise the flow would separate, reducing the duct's efficiency.
-4: NACA duct is only useful in applications where you really don't want much air, at least not as much as you hoped, and certainly less than you expect.
-5: If you want any air at all, make sure the NACA duct is placed in a region with a positive pressure gradient; i.e., put it where the air sees the body as increasing in size, not constant or decreasing.
-6: They don't work well, or at all, when placed on the negative pressure area.
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Some flow comparisons on a RAM vs NACA ducts...
http://www.ivanitski.com/naca-duct-vs-scoop/