While the pressure is important, it is the volume/unit time that dictates
performance. I don't know the LOM engine, but for the sake of discussion
assume it is a 2.5L engine. Then it will require (at full throttle) 2.5
L/min of air! I think there are places on the web that will tell you the
airflow a given sized NACA will provide. Assume that a given setup will
only provide 2.0 L/min at full throttle. Then the hp will be reduced by
25%, so it the volume/unit time can have a significant impact.
Further thoughts.... Engine power is rated at sea level. If our
discussion engine generates 100 hp at full power as it goes up in altitude
it will loose power. The atmospheric pressure at 10,000 ft is 20.58 Vs
29.92 at sea level. The performance of the engine is
(20.58/29.92)100 = 69 hp. You can have a similar effect with the pressure
drop across your air filter. If the drop across your air filter is 5 mm
Hg, then at sea level you will see a reduction of 5/29.92 =17%. This is
why the air intake is up front in most applications. With it being up
front you get a ram air effect and the pressure is greater than 29.92
before the air filter. In most applications effort is put into reducing
the number of turns the air has to take because for every turn there is a
further reduction in pressure. This also helps us understand why
superchargers and turbo chargers are so effective. They actively pump the
air and pressurize the system to combat these effects. Just like a
reduction of 5 mm Hg causes a 15& reduction in performance, a 5 mm Hg
increase will improve performance by 17%.
Hope this helps.
Rick Muller
SR70
-----Original Message-----
From:
scott.hibbs@dcsol.com [SMTP:
scott.hibbs@dcsol.com]
Sent: Saturday, January 11, 2003 11:25 PM
To:
murphy-rebel@dcsol.com
Subject: Air Filter Area ratio to inlet area?
As some of you know, I am putting a LOM in my Rebel. I have decided I have
to
use a NACA duct for intake air with an air filter just aft of the intake.
Does anyone know a recommended ratio of intake area to the air filter? I
want
to keep the pressure as high as possible while passing through the filter.
I
will be using a Bracket type air filter.
Scott
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