Today's Message Index:
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1. 04:11 AM - Re: TeamGrumman-List Digest: 1 Msgs - 09/08/04 (Nichols, James D)
2. 06:59 AM - Re: AA-1 O-320 upgrade Air Box/Intake Geometry (FLYaDIVE@AOL.COM)
3. 10:56 AM - Re: AA-1 O-320 upgrade Air Box/Intake Geometry (TeamGrumman@AOL.COM)
Message 1
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| Subject: | RE: TeamGrumman-List Digest: 1 Msgs - 09/08/04 |
--> TeamGrumman-List message posted by: "Nichols, James D" <james.d.nichols@lmco.com>
Steven,
From experience I have found the air box effects the carb main metering
circuit to the point it runs to the rich side, this manifested itself at
full throttle. The engine ran rough and would not develop full power,
requiring leaning the mixture to get the power up, after the airbox swap
(AA5) the engine did better but still ran to the rich side, I ended up
changing the carb out to a 0-5009 with the new metering valve making it
a 0-5009N, this works outstanding with the AA5 airbox.
JD Nichols AP
N69KV AA1B/150
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Subject: TeamGrumman-List Digest: 1 Msgs - 09/08/04
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Total Messages Posted Wed 09/08/04: 1
Today's Message Index:
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1. 10:49 PM - AA-1 O-320 upgrade Air Box/Intake Geometry (Steven
Jackson)
________________________________ Message 1
_____________________________________
Time: 10:49:56 PM PST US
From: "Steven Jackson" <steven.jackson14@adelphia.net>
Subject: TeamGrumman-List: AA-1 O-320 upgrade Air Box/Intake Geometry
--> TeamGrumman-List message posted by: "Steven Jackson"
--> <steven.jackson14@adelphia.net>
TG,
Can someone explain to me how the size of the intake, air box, etc
affects the way the engine performs--i.e.. is there some type of
equation that gives you the ideal volume or dimensions of the air
intake/air box for a given engine?
The theory on the table is that the stock AA-1 air box is too small for
an O-320 conversion. If so, what would be the ideal size? If a bigger
air box is placed on the plane, would the actual intake on the nose bowl
need to be bigger as well? Would there be an increased drag penalty if
the intake was bigger? My mechanic says there's not much of a ram air
effect with a simple piston plane via the intake on the nose bowl. He
says that the engine sucks in as much as it needs and doesn't get
"forced" air. I'm assuming that there would be a point where the hole
that the engine is "sucking" through would be too small for the engine?
Just looking for some theory and practical application,
Steven Jackson
N1434R
L22
Yucca Valley, CA
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Message 2
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| Subject: | Re: AA-1 O-320 upgrade Air Box/Intake Geometry |
--> TeamGrumman-List message posted by: FLYaDIVE@aol.com
In a message dated 9/9/04 1:53:41 AM Eastern Daylight Time,
steven.jackson14@adelphia.net writes:
> --> TeamGrumman-List message posted by: "Steven Jackson" <steven.jackson14@
> adelphia.net>
>
> TG,
>
> Can someone explain to me how the size of the intake, air box, etc affects
> the way the engine performs--i.e.. is there some type of equation that
gives
> you the ideal volume or dimensions of the air intake/air box for a given
> engine?
>
> The theory on the table is that the stock AA-1 air box is too small for an
> O-320 conversion. If so, what would be the ideal size? If a bigger air
box
> is placed on the plane, would the actual intake on the nose bowl need to be
> bigger as well? Would there be an increased drag penalty if the intake was
> bigger? My mechanic says there's not much of a ram air effect with a
simple
> piston plane via the intake on the nose bowl. He says that the engine
sucks
> in as much as it needs and doesn't get "forced" air. I'm assuming that
> there would be a point where the hole that the engine is "sucking" through
> would be too small for the engine?
>
> Just looking for some theory and practical application,
>
> Steven Jackson
> N1434R
> L22
> Yucca Valley, CA
=============================
Steve:
Easy ... Very Easy.
You are an engine ... Go run around the block ... Go Do IT.
Now take a DRINKING STRAW. Put it in your mouth ... and ... Breathe through
it ... and ... Go run around the block ... Go TRY IT.
No OXYGEN ... No OUTPUT.
Now we all know our engines SUCK .. Or should. But any extra velocity of air
getting into the BOX decreases the work load on the engine sucking in the
air. Velocity and Volume equals Density. The denser the available air with the
least amount of restriction equates to a better breathing engine and More
Horse Power. GHeesh Your A&P should know that!
It does not matter if the density is obtained by a mechanical pump (more
effective of course) or simple RAM AIR. And since RAM AIR is basically Free GO
FOR IT.
The RV-6 intake is angled to be more parallel with the back side of the prop.
This is done because of more slip stream air velocity and more air pressure.
Does it work? Who knows! But every builder has the option of not building
it that way, YET they all do. It's hard to argue with a O-320 and a plane that
cruses at 140 Kts (O-360 = 175 Kts).
Barry
"Chop'd Liver"
Message 3
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| Subject: | Re: AA-1 O-320 upgrade Air Box/Intake Geometry |
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
In a message dated 9/9/04 7:09:41 AM, FLYaDIVE@AOL.COM writes:
> Now we all know our engines SUCK .. Or should.=A0 But any extra velocity of
> air
> getting into the BOX decreases the work load on the engine sucking in the
> air.=A0 Velocity and Volume equals Density.=A0 The denser the available air with
> the
> least amount of restriction equates to a better breathing engine and More
> Horse Power.=A0 GHeesh Your A&P should know that!=A0
> It does not matter if the density is obtained by a mechanical pump (more
> effective of course) or simple RAM AIR.=A0 And since RAM AIR is basically=20Free
> GO
> FOR IT.=A0=A0
>
Oh, no, not again.....
First step. Go to the airport, look at ... say ... a Baron, or hell, even
an RV. Measure the area of the inlet. They are small. When Fletcher built
their IO360 with a constant speed prop, the increased the area of the inlet
by over twice. Hmmm. The plane was slower than a stock Tiger. I told Dave
he could pick up 5 knots by using a stock Cheetah inlet.
The straw analogy is cute, but not very applicable. I've done a sh*tload of
calcs on inlet size. The reality is, 12 square inches, is more than enough.
The faster you go, the SMALLER you need, the higher you go, the larger you
need. If you optimized the inlet size on a Cheetah at 150 knots and 5,000
feet, you would need an inlet of about 3.75 sq inches. AT 12,000 feet and=20150
knots, you need about 8.5 square inches. At 12,000 feet and 100 knots, the 12
sq inch inlet is optimized. On the take off role, an inlet of about 32 sq
inches would be great, but, the spillage drag at 100 knots would scare you.
And, VELOCITY of the air is NOT what you want. Convert all of that energy
into pressure with a properly designed diverging inlet section. RV did this
with their inlet/airbox. Just a note: The RV inlet is really a good design
except for one thing, adding carb heat AFTER you have ice in the inlet/carb
will do nothing. The engine will still quit. They have not provided an
alternate air source for the heated inlet air.
You'll hear me bad mouth the AA5B Tiger airbox (oh, and, by-the-way, the
volume of air sucked of the plenum behind #3 is NOT enough to worry about wrt
bleeding off cooling air) but, the Tiger airbox is just about as close to perfect
as yo can get. I congratulate the engineer on that one. In comparison, the
AG5B airbox is about a bad as can be designed in every respect from
maintenance to airflow. Bad engineering.
The Cheetah inlet is pretty good. It's the right size (sq area wise) but
the aspect ratio is wrong for a decent pressure recovery.
Now, you want to see a really bitchin inlet? Look at the inlet on the side
of the Saratoga or the front of a late model turbo Mooney. Both are a little
large for our needs, 140+ knots at 7500-10000 feet, but they are nice.
Gary
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