Date: Wed, 15 Dec 1999 19:09:56 -0500
Reply-To: Bulley <gmbulley@BULLEY-HEWLETT.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bulley <gmbulley@BULLEY-HEWLETT.COM>
Subject: Re: Air intake "scoops"
Most interesting to my, because on my Air-cooled Vanagon, I know EXACTLY
how air gets from the top of the motor box to the back of the van...through
my motor.
G. Matthew Bulley
Bulley-Hewlett
Corporate Communications Counselors
www.bulley-hewlett.com
Cary, NC USA
888.468.4880 tollfree
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-----Original Message-----
From: Paul Schiemer [SMTP:schiemer@MAGICNET.NET]
Sent: Wednesday, December 15, 1999 3:08 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Air intake "scoops"
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).
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