If I were you, I would not spend a lot of time or money working on that fan setup.
First off, you are correct about the fan moving more cfm than the engine can use. At first look, this seems promising, but because this is a fan and not a pump, it will not be able to produce the pressures required to force the extra air into the engine.
For a real-life analogy:
Consider taking a 5000 cfm box fan and putting it in the doorway of a closet. Then seal up the doorway and turn on the fan. Even though the fan would fill the closet up with air, the fan would not be capable of pressurizing the closet any more than about .05 psi. The fan blades would spin, but the static pressure of the closet would not allow the fan to put any more air into the room.
Now, if you took an air compressor and plugged it into the closet, the pressure would increase, but the volume of air would change only slightly (the walls would expand minutely).
The beauty of a supercharger or a turbocharger is that it combines both an air compressor with a fan. That is why they are so expensive. They must maintain extreme tolerances in order to perform their tasks. A turbo or supercharger with loose tolerances would not be able to create enough pressure to be effective.
On a different note, once the engine reached over 4,000 rpm (figure 23cfm requirement per 1,000 rpm), the fan would only be an obstacle to the flow of the air. You definitely would not want to run with a blockage in your intake path.
If you could find a turbocharger and hook up an electric motor to it, then you may have something, but don't waste your time with a fan.
Dave
