Mr. Bulley wrote:
> So, if I read you correctly, our VW-designed ducts are better than any
> home-grown scoopy-de-doo shapes? Make senses when you reference the
> pressure wave forming and cite the shape of current race-car ducting.

Yes. During testing in a wind tunnel (Lockheed/Martin) a comparison was made
between NACA ducts and a series of (what is called) 'positive shape'
scoops. ['Scoops' were items that protruded beyond the surface of a panel,
in a number of different materials and shapes. 'Ducts' were cut into the
panels for that part of the testing.]
Goal for the testing was to see if the volumetric increase of flow (called
SCFM) was substantially better with a duct or a scoop.
Measurements were made from 5 mph to 200 mph, all telemetry (24 points) was
fed into a computer and analyzed. A graph was produced for comparison
purposes. [This is real simple stuff, don't want to make it sound
like voo doo.]

Across the board there was a point where the scoop outperformed the duct,
but, the duct delivered more volume when compared to the entire breadth of
velocity. In other words; the duct was better, overall, than the scoop,
although the scoop was best at one spot. [There was some ramping effect, as
the velocity approached optimal performance for the scoop. Although, beyond
that point, the performance dropped with almost the same exponential curve.]
Problem with scoops on cars is that you drive at varying velocity, and
rarely do you get into the 'sweet spot' of the scoop.

Also, a thing to remember about moving air into the engine compartment; it
has to have a place to go afterward. I'll bet there aren't many here who
know where the outbound ducting is on the average vanagon.
You can force a lot of air into a cavity but it's just as important to
remove it as quickly as it goes in, otherwise it becomes dormant (useless).