REFLECTOR: ram air vs filter
Jack Sheehan
jsheehan at ncam-sats.org
Mon Jun 18 12:38:38 CDT 2007
John,
No I have not done that as a static test.
JackAt 02:17 PM 6/15/2007, you wrote:
>Jack,
>
>Do you have static MP values of the ram air vs. filtered air - vs. ambient?
>
>Also - what model of engine do you have? Any mods - higher compression, etc?
>
>Any pictures of your scoop?
>
>John
>
>________________________________
>
>From: reflector-bounces at tvbf.org on behalf of Jack Sheehan
>Sent: Fri 6/15/2007 10:06 AM
>To: Velocity Aircraft Owners and Builders list
>Subject: Re: REFLECTOR: ram air vs filter
>
>
>I have had very good performance with the
>alternate air system from airflow performance
>http://www.airflowperformance.com/. I actually
>use it differently. The photo is looking up at
>the engine the straight tube ( without the
>filter has the butterfly valve controled by a
>cable. In the open position the induction air
>comes thru the air scoop under the belly through
>scat tube making a S bend up to the fuel
>controller. This provides Ram air. If the
>environment is bad ie dust rain sleet etc
>(ground operations), I close the ram air and
>induction air is thru the K&N filter. The K&N is a RU-2790
>There is almost 1 inch difference in manifold
>pressure due to the Ram air. Take off on the
>filtered air or unfiltered(ram ) is essentially
>the same since the effect of ram at slow
>airspeed is very little.. I thought the
>increased temperature of using air from within
>the engine compartment would cause an issue but
>it has not. The idea was to keep the filter
>protected from the elements so it would not clog due to ice dirt etc.
>the air scoop I used was one velocity sells it
>was a mold used under the wings of older models.
>
>Jack
>N55XL
>Race 55
>
>At 10:14 AM 6/15/2007, you wrote:
>
>
> Scott,
>
> Yep, my air intake does take a turn
> over 90 degrees and I will have some measure of
> disturbed flow in there. It is a compromise
> design like so much of this is. I am not sure
> we need a ram air. The engine intake will suck
> air sufficiently, hopefully, thru that turnit
> is shortest distance I can make it with a
> pretty straight run after that. We are talking
> a short distance. I know airliners are not a
> good comparison, but I did have these jet
> experiences that I included (best I recall) as
> Collier and I discussed the issue. The B-727
> center engine is actually in line with the two
> pod engines thru a big S duct. I was unheard
> of at the time. Compressor stalls were is big
> issue on start up or even on the ground when I
> guy would make a rolling takeoff in a big
> crosswind the pour the coals to it with inlet
> air all disturbed. It took some testing in
> the early development years but it
> works. Douglas, in the DC-10, rejected it in
> its bigger trijet, while Lockheed in the L-1011 included it.
>
> Of course cylinders sucking air are
> different than compressor blades which are more
> flow sensitive. I opted for what we did. My
> thinking for anybody not up to this point could
> include these points: I saw Chuck Jensen's
> intake. He uses a portion of what would be
> cooling air by ducting out of his roof
> NACA's. (And his intake ducting took some big
> turns too, and didn't have a lot of ram quality
> to it per se.) He never mentioned any oil
> temp/cooling issues that I recall. I think a
> good hunk of that approach would have to
> include a good cooling plenum. I never asked
> him about this, but I am glad myself to have
> the space free for other stuff in the
> engine-block-to-firewall real estate. Lots of stuff has to go there.
>
> Belly intakes maybe like Rene would be
> the best for ram air advantage. His has worked
> too, based on his 500 hours. I would worry
> about sucking in water/slush kicked back from
> the nose tire. That was a problem in the later
> stretched versions of the DC-9. In fact they
> put mud flaps on the nose tire. For us...well
> we are not all weather operators. Personally,
> I would, and I bet most others would delay a
> takeoff or landing if there was active moderate
> precip that could otherwise be avoided for lots
> of reasons other than intake debris. Just my 2
> cents. Oh, and thanks. I guess it is a K&N filter not K&M.
>
> Terry
>
>
>
>
>________________________________
>
> From: reflector-bounces at tvbf.org [
> mailto:reflector-bounces at tvbf.org
> <mailto:reflector-bounces at tvbf.org> ] On Behalf Of Scott Derrick
> Sent: Thursday, June 14, 2007 9:34 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: ram air vs filter
>
> Terry,
>
> are you blowing air backwards through
> the K&N? Does it matter which way the air
> flows. into the cone or out of the cone?
>
> Scott
>
>
> Terry Miles wrote:
>
>
> Keith,
>
>
>
>
>
> Here's what I got...mostly
> this is a Malcolm Collier/Hangar 18 effort.
> He
>
>
> did the actual carving, and
> it was his idea. I took it from there. I
> can
>
>
> send more pics if you need
> them. It is the carved foam block routine.
> Note
>
>
> the scoop is away from the
> underside of the wing, and you can see the
> outlet
>
>
> duct going into what would
> be the eng compartment. We will use a short
> hunk
>
>
> of hose to connect.
> The wing root section fits the standard
> size
>
>
> rectangular K&M filter
> and has the suction 2ndary door on a spring
> for
>
>
> filter
> bypass.
>
>
>
>
>
> The intake plenum that came
> with the engine didn't work. Mine now goes
> off
>
>
> to the right at about 35
> degrees (to the left if you talk to Don
> George!)
>
>
> He was good about swapping
> out the straight on one we had to begin
> with.
>
>
> I've got the Ly 540.
> I think there are 3 different
> induction
>
>
> chambers/plenums whatever
> they are properly called. They come on and off
> w/
>
>
> a couple of
> bolts.
>
>
>
>
>
>
> Hope this inspires!
> Good luck.
>
>
>
>
>
>
> Regards,
>
>
> Terry
>
>
>
>
>
>
>
>
> -----Original
> Message-----
>
>
> From:
> reflector-bounces at tvbf.org
> [mailto:reflector-bounces at tvbf.org]
> On
>
>
> Behalf Of Keith
> Hallsten
>
>
> Sent: Tuesday, June 12,
> 2007 9:05 PM
>
>
> To: 'Velocity Aircraft
> Owners and Builders
> list'
>
>
> Subject: Re: REFLECTOR: ram
> air vs filter
>
>
>
>
>
> Rene',
>
>
>
>
>
> This sounds like a pretty
> practical set-up for induction. Do you have
> any
>
>
> pictures? Is the
> "midline scoop" available, or was that a one-off
> custom
>
>
> part?
>
>
>
>
>
> I am in the midst of engine
> installation, and the induction system seems
> to
>
>
> be the part I'm having the
> most trouble with. I have made a couple of
> air
>
>
> boxes using the "lost
> foam" method, but found their design to
> be
>
>
> unsatisfactory. I'm
> definitely looking for inspiration on
> this.
>
>
>
>
>
> Keith
> Hallsten
>
>
> XLFG, Roseville,
> CA
>
>
>
>
>
>
>
>
> -----Original
> Message-----
>
>
> From:
> reflector-bounces at tvbf.org
> [mailto:reflector-bounces at tvbf.org]
> On
>
>
> Behalf Of Rene
> Dugas
>
>
> Sent: Tuesday, June 12,
> 2007 4:22 PM
>
>
> To: 'Velocity Aircraft
> Owners and Builders
> list'
>
>
> Subject: Re: REFLECTOR: ram
> air vs filter
>
>
>
>
>
> I use the midline scoop
> mounted to the lower cowl and the rear of
> the
>
>
> fire wall. I used a K
> & N cone shaped filter mounted to a 3
> inch
>
>
> aluminum flange with an
> identical flange mounted the opposite
> direction
>
>
> in a fiberglass box.
> This is attached to the induction by 3 in.
> scat
>
>
> tubing to allow for
> vibration. I mounted a spring operated door in
> the
>
>
> side of the box for
> emergency air that sucks open if I close the
> scoop.
>
>
> I made the box by forming
> foam and coating it with glass. I
> used
>
>
> acetone to dissolve the
> foam and presto custom air box. I seem to get
> 1
>
>
> to 2 inches of MP based on
> side by side flights with others at
> the
>
>
> Velocity
> Symposium.
>
>
> My scoop starts out about
> 1.75 by 2.25 inches and opens up
> into
>
>
> approximately a one foot
> square air box with the K & N in
> it.
>
>
> Just FYI. I can
> remove the lower cowl and the scoop screws to the
> box.
>
>
> I can remove the two screws
> in the scoop and remove the filter
> for
>
>
> cleaning.
>
>
> Rene'
>
>
>
>
>
> -----Original
> Message-----
>
>
> From:
> reflector-bounces at tvbf.org
> [mailto:reflector-bounces at tvbf.org]
> On
>
>
> Behalf Of
> Tom
>
>
> Sent: Thursday, June 07,
> 2007 8:01 PM
>
>
> To:
> reflector at tvbf.org
>
>
> Subject: REFLECTOR: ram air
> vs filter
>
>
>
>
>
> My problem was that I went
> from ram air to what was too small of a
>
>
>
> filter. It was a 3"
> diameter x 5" long. I clamped it directly to the
>
>
>
> induction air tube. I
> really need a larger filter with filtration on
> the
>
>
>
>
>
> end also (this was closed).
> Very space limited under there as I share
>
>
>
> the ram air inlet with a
> 2nd oil cooler mounted on the baffling. (large
>
>
>
> aeroduct hose). I may just
> go with a
> screen.
>
>
>
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