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Originally Posted by pecivil
Water may have been why....but water does not flow uphill, so as long as the actual intake structure is decent distance above the duct you should be ok?
of course you would be screwed if you tried to drive through a flow high enough to completely bury the duct, but that would be 18" or more of water......enough to think if it was raining that hard, you would not be in the boxster, eh?
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Hi,
NACA (National Advisory Committee for Aeronautics) was the precursor of NASA (National Aeronautics and Space Administration) and was founded during WWI to bring Industry, Academia, and Government into concerted Aviation Research.
After WWII, when Jet Aircraft were in their infancy, it was found that at very high trans-sonic speeds and beyond that the traditional ducts would not flow due to a pressure boundary being setup within the duct itself. NACA Ducts were developed to be effective in supersonic flight.
Part of my Thesis for my MS involved studies of flow qualities in NACA ducts, and frankly, then as now, usually gives me a headache what with all the dynamics involved...
Racing adopted NACA ducts because they left the skin of the car
clean, improving the car's aerodynamics. The OEM intake is a form of NACA duct. It does not protrude very far above the skin's surface and yet provides significant airflow to the engine and engine bay.
Ram Air again is a relatively high-speed phenomina and except for some special cars with very large intakes and air-hungry engines, they produce little effect and are mostly for aesthetics. In the realm of proper flow, a 90° bend such as these CF Intakes have is less efficient in terms of flow than those with lesser degrees of bend, so I suspect the OEMs are more efficient.
There have been numerous instances where the existing OEM intakes have gulped enough water in driving rain storms and high-pressure washes to cause an engine to hydro-lock, essentially destroying the engine. I suspect that Porsche discovered this in the prototype and raised the Intakes to lessen (but apparently not eliminate) this possibility...
Happy Motoring!... Jim'99