> > > > >>Ram air box truths (real PSI gain)
 > > > > >>Gentlemen,
 > > > > >>This issue has been explored and many of us have spent

hundreds

 of
 > > > dollars
 > > > > >>or many hours to install a RAM air box in our aircraft to

gain

 an
 > > > expected
 > > > > >>increase in performance. Truth be told, there isn't much

gain

 under
 > 200
 > > > > >>mph. At least not enough to even register on the airspeed
 indicator.
 > > > I'll
 > > > > >>explain why and you can decide for yourself.  This is

probably

 why
 > no
 > > > one
 > > > > >>will quote any increase in speed when you purchase a RAM

airbox

 from
 > > > them,
 > > > > >>because there won't be any.
 > > > > >>Here are the true hard facts using the following criteria:
 > > > (Publication:
 > > > > >>Aerodynamics and Flight)
 > > > > >>At   MSL Pressure 14.7 psi  (densest air possible on the
 planet)
 > > > > >>At   200 MPH (if your plane will go this fast) direct air

flow

 (non
 > > > > >>obstructed, perfect flow)
 > > > > >>At   59.02 degrees F  (15 degrees C)  Standard aeronautical
 > calculation
 > > > > >>temp at MSL
 > > >
 > > > > >>TOTAL INCREASE IN PRESSURE =  0.710 psi
 > > >
 > > > > >>By the way, any performance increase is assuming that there

are

 zero
 > > > bends,
 > > > > >>curves, voids, filters elements or any other
 disturbance/blockage of
 > the
 > > > > >>flow into the cylinder head ports. And we all know that

isn't

 the
 > case
 > > > in
 > > > > >>our aircraft or engine induction design.  Now, go ahead and
 factor
 > in
 > > > > >>actual conditions and temp at 2000 to 8000 ft MSL along

with

 your
 > actual
 > > > > >>airspeed (indicated pressure) and the fact that you are not
 getting
 > > > > >>true/undisturbed RAM air into your PERFORMANCE DESIGNED
 Lycoming
 > > > >>induction system.
 > > > > >>You might see 1.5 HP at 2900 RPM's on an 0-320 engine

running

 Wide
 > > > > >>open Throttle.  Just don't pack a lunch before flight,

you'll

 get
 > the
 > > > same
 > > > > >>results.
 > > > > >>Just passing along mathematical facts.

 > This guy betrays his own lack of 'mathmatical facts'.  Since engine

HP

 is
 > almost directly related to available manifold pressure, the HP

increase

 > using HIS numbers would be 7.727 HP.  (.710 / 14.7 =  4.829%   *

160 HP

 =
 > 7.727)
 >
 > Ever seen a formula 1 racer NOT use a ram air inlet?
 >
 > Tracy Crook
 > tcrook@rotaryaviation.com
 > www.rotaryaviation.com

[Todd TC. Carrico]
What if the RAM inlet also happens to be in a high pressure area such as
under a wing?  Too many variables to make generalizations.

tc

That is a good place for it.

Paul Lamar
 
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