naca duct in hood
02-26-02, 03:58 PM
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naca duct in hood
Have any of you non turbo guys thought about putting a naca duct in your hood? I am getting ready to repaint my 7 and replace a damage hood. I have been thinking of something similar to the one on a viper. The duct would not protrude up off the hood and no one would confuse my car with a turbo. First thought of this as mainly for cosmetic reasons but I am sure some type of ram air set up could be made to feed my k&n filter.
02-26-02, 04:12 PM
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The top of the hood is in a vacuum at speed, so you would get no ram air effect, but rather a slight negative pressure effect which would reduce your performance at high speed. On the good side, you would get cooler air, which would give you better performance off the line. All in all, I would think that you would get just about the same performance with that NACA duct as you would if you just used a drop-in K&N filter with your stock intake system. The NACA duct would look cool, though. 
http://www.geocities.com/mcgumrapper/aerodynamics
BTW, you can get pre-made NACA ducts from most race parts suppliers.
http://www.geocities.com/mcgumrapper/aerodynamics
BTW, you can get pre-made NACA ducts from most race parts suppliers.
02-27-02, 07:05 PM
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The pressure is low relative to ambient pressure. Low pressure air does not mean no air, it just means lower pressure. I have heard rumors that the airflow through the IC scoop reverses at high vehicle speed, however I have personally tested a TII hood scoop up to 90mph, and it still flows air just fine. I had a difficult time believing the air reversal theory, anyway, as I don't see how the slight drop in pressure could overcome the strong momentum of the air flowing into the forward-facing hood scoop. Also, assuming a high vehicle speed, the lower-pressure high-velocity air will dramatically decelarate as it contacts the IC core, which will increase the pressure. I noticed that the air appears to have trouble traveling through the IC core at higher speeds, so one of these days I'll continue my testing with a TII hood on an NA or FMIC-equiped TII to see what the scoop is really doing.
If you really want to improve your airflow, I recommend getting an aftermarket EMS which will allow you to ditch your restrictive AFM, and replace it with a bellmouth intake (air horn, trumpet, etc.) and high-flow air filter. You could still feed this system with a NACA duct if you like.
If you really want to improve your airflow, I recommend getting an aftermarket EMS which will allow you to ditch your restrictive AFM, and replace it with a bellmouth intake (air horn, trumpet, etc.) and high-flow air filter. You could still feed this system with a NACA duct if you like.
