Today's Message Index:
----------------------
1. 12:35 AM - Re: Cooling issues, once again! (Brian Davies)
2. 10:15 AM - Cooling issues, once again! (Erich Trombley)
3. 12:13 PM - Re: Cooling issues, once again! (Frans Veldman)
4. 12:40 PM - Re: Re: Cooling issues, once again! (Frans Veldman)
5. 12:41 PM - Rotax 914 Intercooler (Frans Veldman)
6. 01:04 PM - Europa - Battery cable sizing (Bob Fairall)
7. 02:09 PM - Re: Cooling issues, once again! (zwakie)
8. 02:29 PM - Re: Europa - Battery cable sizing (Kevin Klinefelter)
9. 02:47 PM - Re: Rotax 914 Intercooler (Kevin Klinefelter)
10. 02:56 PM - Re: Cooling issues, once again! (rparigoris)
11. 03:13 PM - Re: Rotax 914 Intercooler (rparigoris)
12. 03:30 PM - Re: Europa - Battery cable sizing (rparigoris)
13. 03:42 PM - Re: Europa - Battery cable sizing (Bob Fairall)
14. 04:42 PM - Combustion air inlets (Fred Klein)
15. 11:22 PM - Re: Combustion air inlets (Frans Veldman)
16. 11:48 PM - Re: Combustion air inlets (Fred Klein)
Message 1
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| Subject: | Cooling issues, once again! |
I run have run Evans from new, with completely standard installation and no
cooling problems. Max OAT I have experienced is 28C. I suspect some of the
problems with Evans have been caused by switching to it from standard 50:50
without getting rid of every last drop of the old stuff before using Evans .
The instructions do warn of this problem.
Brian Davies
912S Trigear
_____
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Robert Hatton
Sent: 05 June 2010 23:18
Subject: RE: Europa-List: Cooling issues, once again!
I have been following the cooling topic and wondered what the forum thought
about using Evans coolant?
I noticed Kevin uses Evans from his Death Valley flight description, but
Mike Parkin threw his away!
I am about to refill my radiators and was considering Evans as the way to
go. I am based in Colorado and expect hotter temperatures in the summer than
northern Europe and cooler ones in the winter.
I would welcome anyone's advice and experiences.
BTW - on my 912UL installation the Oil cooler was lowered and made a
dramatic difference - stable temperatures and no sign of overheating when
the aircraft was flying in the UK. I am considering lowering the Oil Cooler
for my 914 installation for the temperatures get up to the high end of the
scale during climb out, but do stabilize in the cruise.
Robert Hatton
email: roberthatton1@googlemail.com
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of GRAHAM
SINGLETON
Sent: Saturday, June 05, 2010 9:38 PM
Subject: Re: Europa-List: Cooling issues, once again!
You could be right there Frans. btw theory says that cowl inlet should be
much smaller than rad area so that some pressure recovery can happen, also
lips must be smooth.
Graham
_____
From: Frans Veldman <frans@privatepilots.nl>
Sent: Saturday, 5 June, 2010 21:27:33
Subject: Re: Europa-List: Cooling issues, once again!
On 06/05/2010 09:26 PM, Rob Housman wrote:
Looking closer to both radiators, It appears to me that the oil cooler
has closer spaced fins, thicker fluid canals, and an overall smaller
useful area.
It might be that this is the reason why lowering the oil radiator also
causes the water tem/Navigator?Europa-List" ="http://forums.matronics.com"
target="_blank">http://forums.matronics.
 tronics.com/contribution"
target="_blank">http://www.matronics.com/contri===============
http://www.matronics.com/Navigator?Europa-List
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| Subject: | Cooling issues, once again! |
Frans,
I have a one off custom FWF that uses the stock engine mount, water rad
iator and oil cooler (located one behind the other which in many aspects
is close to what you have done). I had a very similar experience to yo
urs in that I conducted my first flight in January when temps were mild
and as summer approached I ran into major cooling issues just as you des
cribed. I do not believe dropping the oil cooler will do anything for y
ou if your design is like mine in that it is properly sealed around the
inlet of the water radiator. Because my water radiator and oil cooler a
re in line I have sealed the space between them on the top. The sides a
nd bottom are sealed around the sides of the cowling. I will try and po
st a picture of this. Anyway, what Rob states below about heat transfer
is spot on. You need to look at it as a system. In addition the oil a
nd water dog house which measures 2.375" x 7.375" at the inlet, my init
ial design had two very small round openings (2" diameter) in a location
close to the stock cowling.
Like Kevin I am able to climb out at high power settings (usually 31" MP
) to the high teens without issue so long as I don't go slower than 90 K
IAS. This limits the nose high attitude. Any slower and I will start t
o overheat. BTW I live in Las Vegas, NV and we have been know to have a
warm day every now and then. Yesterday we hit 108 deg F.
This is what I did to solve my cooling problem which was pretty straight
forward: I enlarged the 2" diameter holes to create a horizontal teardr
op. The extra air flowing over the top of the engine was sufficient to
keep it cool both on the ground and during climb. I also use Evans cool
ing which did increase my temps by about 10 degrees C over 50/50 water &
antifreeze but provides a higher boiling point. I was initially tempte
d to lower the oil cooler, however, this would have been a major modific
ation with my design, so that was out and it was doubtful from a system
perspective if this would have really helped. It is another matter if I
had the stock Europa cowling since there is a large gap at the bottom o
f the cowl and lowering the oil cooler fills this space preventing the a
ir from bypassing around the radiator and oil cooler. I didn't have thi
s issue with my design as noted above. So, two options were left, incre
ase the size of the oil cooler and radiator, or open up the round holes
to provide more flow over and around the engine. The latter was the eas
iest to option and worked out well for me. My guess though is that a la
rger radiator and oil cooler, retaining my original 2" holes would resul
t is the least drag option. Keep in mind I am near red line during clim
b usually around 125 deg C. on oil temp which leads CHT. I hope the ab
ove is helpful.
Good luck.
Erich Trombley
N28ET Classic Mono 914
Time: 12:38:50 PM PST US
From: "Rob Housman" <europa@hyperion-ef.com>
Subject: RE: Europa-List: Cooling issues, once again!
While it is true that "heat transfer is directly proportional to tempera
ture
difference" that does not tell the whole story. First, remember that th
e
relevant temperature difference is the difference between the temperatur
e of
the fluid on the inside and the air on the outside, and even with pre-he
ated
air the second radiator could have the same delta T as the first radiato
r.
I'll grant you that there is probably a difference, however.
Also relevant, and non-trivial, are the area of the heat transfer surfac
e,
the flow rate of the liquids inside the heat exchangers (radiators, in
common aircraft and automotive parlance), the flow rate of the air outsi
de
these heat exchangers, the heat transfer coefficients for each of the fl
uids
involved, the heat transfer coefficients of the materials from which the
radiators are made, the effect of any scale or similar deposits on the h
eat
transfer surfaces (both inside and outside), Reynolds numbers for the
flowing fluids (a function of flow rates and fluid properties), and the
physical properties the radiators and of the coolant and oil flowing wit
hin
the heat exchangers.
Having said all of that, there is no doubt that "re-using" the cooling a
ir
will affect heat transfer within the radiator using pre-heated air, and
this
is undoubtedly why Europa recommend placing one below the other.
Best regards,
Rob Housman
Irvine, CA
Europa XS Tri-Gear
A070
Airframe complete
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Robert Borg
er
Sent: Saturday, June 05, 2010 11:02 AM
Subject: Re: Europa-List: Cooling issues, once again!
Paul,
I don't see how it can. Simple thermodynamics is against it. Heat tran
sfer
is directly proportional to temperature difference. Both radiators are
at
about the same temperature. Once the air has been heated by the first
radiator its ability to accept heat from the second has been greatly red
uced
if not eliminated.
And this is assuming that the area below the radiators has been sealed s
o
that the air goes through the radiators and not under them, doing no goo
d at
all.
Check six,
Bob Borger
http://www.europaowners.org/N914XL
Europa XS, Short Wing, Intercooled Rotax 914
rlborger@mac.com
Cel: 817-992-1117
On Jun 5, 2010, at 11:43 AM, Paul McAllister wrote:
Hi All,
I am curious to know if there are any examples of standard XS cooling se
t
up's that do not have the oil radiator lowered that work fine.
Thanks, Paul
____________________________________________________________
New Era Diets (SHOCKER)
Simple weight loss secret to lose 12 pounds in 30 days
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| Subject: | Re: Cooling issues, once again! |
On 06/06/2010 07:07 PM, Erich Trombley wrote:
> I have a one off custom FWF that uses the stock engine mount, water
> radiator and oil cooler (located one behind the other which in many
> aspects is close to what you have done). I had a very similar
> experience to yours in that I conducted my first flight in January
> when temps were mild and as summer approached I ran into major
> cooling issues just as you described.
It looks indeed like your setup is quite similar to mine.
Just like you, I can't drop the oil cooler without major modifications.
> This is what I did to solve my cooling problem which was pretty
> straight forward: I enlarged the 2" diameter holes to create a
> horizontal teardrop. The extra air flowing over the top of the
> engine was sufficient to keep it cool both on the ground and during
> climb.
I have two naca ducts in the top cowling with a diffuser angled down so
it dumps the air on top of the cylinders. After some testing, I believe
that in my situation the answer should not be found in increasing the
cowling airflow. Reasons are:
1) There are no signs of elevated temperatures inside my cowling. No
color changes, no melted plastic parts, etc.
2) I had the large 3" stock cowling inlets plugged, but openen them
again in the hope that this would enhance cooling. Well, it didn't.
There was a very slight improvement in ground cooling, but not in flight.
3) As the Rotax engine is mainly water cooled, it is more efficient to
cool it by water than by air. All air taken away from the front of the
airplane reduces pressure recovery and results in more drag. So we
should try to use the cooling air as efficiently as possible. True, if I
remove the cowling completely the engine runs much cooler. But how much
drag are we creating with that?
The more I learn about this subject, the more clear it becomes to me
that two radiators in series is a bad design. The front radiator has no
free exit, the air flow is impeded by the second radiator. This severely
reduces air flow through the radiator. Less airflow is less cooling. The
second radiator receives hot air from the first radiator. Less
temperature difference is less cooling. Also this radiator suffers from
reduced airflow because of the drag of the first radiator.
So, as it already turned out that two radiators in series doesn't work
well in my case (and in the case of the majority of the forum members)
I'm going to change it.
(In your situation it works, but even with your enlarged cowling
openings, you are still balancing on the red line and have to limit
climbing to less than Vy. It is better than what I have now, but now I
have to work on it anyway, my goal is to solve the issue completely.)
The idea is now to take the oil radiator completely away, so the water
radiator can vent the air freely. For the oil radiator I will take a
smaller one (everyone reports too much oil cooling once the oil cooler
is lowered and it is no longer fed with hot air), fit it somewhere else
in the cowling, and connect it with a scat tube to a dedicated air inlet.
Additional advantage is that I can put a butterfly valve in the scat
tube and so reduce the cooling air for the oil cooler in winter (or
during warm up), which I think is better than a thermostat (less oil
line connections, and less drag: we are not going to spend energy to
drag air through a radiator while we actually don't want to cool the
stuff inside at all). For the moment I will dump the exit air from the
oil cooler inside the cowling. The 914 equipped Dimona does it that way,
and it tows all day long gliders with full power at no more than 50
knots, in hot weather, without any cooling issues. If really needed I
can give it a dedicated output, but for the moment I will try it this way.
The Rotax manual says that the water radiator releases 30 kW and the oil
cooler 7 kW. So, the oil cooler accounts only for about 20% of the total
heat release. I think it is a good idea to separate it totally from the
water radiator.
Thanks for sharing your experiences!
Frans
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| Subject: | Re: Cooling issues, once again! |
On 06/06/2010 12:49 AM, rparigoris wrote:
> I have incorporated a
> rich switch that activates the enrichment solenoid at will
A good idea. I like it for emergency use, but to use a richer mixture to
solve cooling flaws is something I consider a last resort.
> mogas
> with alcohol will run leaner than mogas without alcohol,
Good point. I use mogas, but haven't bothered too much to see if there
is alcohol inside.
> Constipation is a big problem, Ira mentioned using an
> airspeed indicator to see where high and low pressure area is.
Good idea as well. Guess it is time to source ebay for a used ASI.
> I will also use two model aeroplane electric motors to exhaust through
> gills on ground and in climb.
Well, I'm not too fond of this idea. It is somewhat strange to have to
use fans in a vehicle that has already a large big fan in front, and
which moves fast by nature. There is plenty of airflow available, it is
just a matter to find a way to let physics do the work for you.
> I will have my exhaust coated with a coating
> that is supposedly time tested from Rotax research arm, limits some
> heat going into cowl. If I want to limit more heat going into cowl
> will wrap exhaust, but makes for harder inspection.
Keep in mind that heat release is actually a good thing. Heating the air
inside the cowl increases the volume of the air, and thus creates extra
pressure on the exit. This reduces drag. Jet engines work that way as
well. ;-)
Further, the cooler the air escaping from the exhaust, the less noisy it
is, and the less turbulence it causes. This again results in less drag.
With a proper airflow inside the cowling (from top to bottom) you are
using waste cooling air from the cylinders to cool the exhaust tubes.
This heated air should just go to the exit, and nowhere else. If this is
the case, it is worth cooling the exhaust as much as possible.
> Using something like an automobile windshield
> washer pump and spray head misting radiators with water could keep
> you cool till you hit on something that works.
This means I would have to install a water tank, carry water as ballast,
install electrics, etc. I think in the same time I could relocate the
oil cooler. If the vendors cooperate, I will be flying again within a week.
Frans
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| Subject: | Rotax 914 Intercooler |
Talking about cooling...
I have the intercooler for the Rotax 914, per factory setup.
My airbox temperature sensor shows no difference if I seal off the
intercooler!
While solving my cooling problems, I learned a few things:
1) Naca ducts provide no ram air, but merely "allow air to get in".
2) The cowling is somewhat "pressurised" by the openings in front.
How is the intercooler supposed to work, "connected" on the inlet to a
naca duct which provides no pressure, and the outlet venting into a high
pressure area?
I know quite some folks are flying around with an intercooler. Has
anyone indeed measured the drop in temperature? Has anyone ever found
bugs or other contaminations in the radiator? If so, were they on the
bottom or on the top of the radiator?
Frans
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| Subject: | Europa - Battery cable sizing |
Hi all,
Please may I have some advice on battery cable size.
My existing Europa uses 2AWG cables. In the interests of weight saving, on
my new 'XS' Mono I have started installing 4awg cable for the approx 7'6"
run. However, I'm now a little concerned that 4awg will be sufficiently h
eavy.
Many thanks in anticipation.
Bob Fairall
Kit 71 - 420 hours and going strong.
Kit 494 - getting there!!
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| Subject: | Re: Cooling issues, once again! |
Frans, sorry to hear about your oil-cooling issues - but it lead to an interesting
discussion that I follow with great intrest.
Next time we're both on the field, could you have a look at my setup? I have some
ideas that I would like to run by you...
--------
Marcel
(Classic Tri-Gear PH-MZW - formerly G-BWON)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=300248#300248
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| Subject: | Re: Europa - Battery cable sizing |
Hi Bob,
the link below will show you an option that I and many others have
used.The 4awg is serving me well in my XS mono 914
Kevin
http://www.periheliondesign.com/fatwires_files/fatwire2flyer.pdf
----- Original Message -----
From: Bob Fairall
To: europa-list@matronics.com
Sent: Sunday, June 06, 2010 1:03 PM
Subject: Europa-List: Europa - Battery cable sizing
Hi all,
Please may I have some advice on battery cable size.
My existing Europa uses 2AWG cables. In the interests of weight
saving, on my new 'XS' Mono I have started installing 4awg cable for the
approx 7'6" run. However, I'm now a little concerned that 4awg will be
sufficiently heavy.
Many thanks in anticipation.
Bob Fairall
Kit 71 - 420 hours and going strong.
Kit 494 - getting there!!
______________________________________________________________________
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| Subject: | Re: Rotax 914 Intercooler |
Hi Franz,
Very interesting. Have you tried this sealing off the intercooler up at high
altitude? I think the cooler should be doing more "work" the higher you are
cruising?
I don't have an airbox temp sensor, but I wish I could repeat your test
below. I too have the factory setup installed. You pose some interesting
questions on the installation. I wonder if air is flowing though the cooler
from the naca inlet as designed?
Kevin
...
>
> I have the intercooler for the Rotax 914, per factory setup.
> My airbox temperature sensor shows no difference if I seal off the
> intercooler!
>
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| Subject: | Re: Cooling issues, once again! |
Hi Frans
Sounds like you are getting off to a good start.
A few points to make, and a few I disagree with
**Ask any Rotax distributor in the know, they want a 914 to run well below edge
of redline for longevity. Not too cold, but near the lower end is preferable.
I think we can agree on this. Lockwood loves the temps on his aircam in the air,
but hates them in water making a long taxi (twin 914 or 912S pusher)
**Now here is where I don't agree with you. True there is a big fan upfront, and
seems foolish to also add little fans to unconstipate the cowl. In a properly
designed cowl/cooling system I agree. I don't believe the europa has a properly
designed cooling system. I don't think it is too too draggy, but taxi on ground
and climb it is for certain less than ideal. Unless you increase drag more
than desired all the time, I rather dump some amps to do the deed on ground
and in climb than engineer an entirly new system. It also gives a side benefit
of being able to cool down cowl after shut down. Europa uses a smaller frontal
area radiator than many other Rotax installiations with same total area. This
means you need a faster flow. In cruise you have that faster flow, but let
me see you make that fast flow on ground and in climb? Lets see how Diamond works
at 50 knots with Rotax radiator? I forget, perhaps Karl?? used a larger frontal
area radiator with good results i think with intake similar to yours. Anyway
I am installing a fan that can in-fact create a lot faster airspeed than
the prop in those configurations ever could by themselves. You make a pretty weak
case that temps are fine in cowl because you don't see any plastic discolored.
My gut feeling is after a hundred hours you probably will. Plastic takes
a while before it becomes discolored and brittle in many instances. Measure please
so there is no doubt. I bet you find stalled air not making its way out as
fast as you would like. The exit area of Europa is less than ideal, especial
when you dump intercooler air in there. I disagree that heating cowl air is a
good thing. Yes on fast glass, or a P-51 you can accelerate air faster and easier
to airspeed on exiting and decrease drag a bit. That said you could close
all intakes or exits on cowl and reduce drag a little more, of course this does
not benefit cooling which is an issue. If cooling was not an issue, then drag
reduction is a good thing to chase. On Europa you will almost for certain heat
the da!
rn engin
e up exhaust. There is not a trivial amount of BTUs given off from the exhaust
and turbo, it can easily heat motor where through water, oil, air and gas (enough
carbon monoxide per Rotax reccomondations) cooling, will not enough to lower
the temps to liking. There is enough intake air charging through Europa cowl,
yours included where if you are heating it, it means air is getting constipated.
I think it is very safe to say the discharge of a typical stock XS trigear
exit air or your plane is nowhere near as good a design as a P-51 or Gilles
exit design. Measuring temps and pressures is best way to make informed decisions.
Be more concerned on ground and in climb than in cruise. With top cowl off
there is not much in way of constipation. The two gill fans are easy to try,
it semi replicates having the top cowl off. The motors are probably under 10
bucks for the two, and props and hubs about the same. If you find they lower
temps and pressures leave them in place. If they do nothing then take them off.
Same goes with rich switch. If you can climb between 85 and 100% power and lower
temps, then that is a good thing. Colors of spark plugs running mogas is
not too reliable of an indicator. running 100LL is better, but you would need
to shut down after a run at 100% and 115% to measure to get most reliable reading.
Carbon monoxide the most accurate and reliable method. True burning a tad
more fuel with rich switch, but way way easier on motor until you can verify
with carbon monoxide detector. Also a good thing to fool with, if you see at 100%
power when you richen the EGTs first go up before they go down, or even stay
still for a bit, you are either lean of peak or at peak. A leak where you have
a slight high EGT can be adressed too. Alcohol in gas will lean mixture compared
to fuel with no alcohol. Type 64 carb on 914 does not compensate mixture
via a 02 or carbon monoxide sender, they are fixed. Run alcohol, will run leaner.
On a car run more alcohol, will compensate if it uses a o2 sender system.
Anyway unconstipating air will most likely benefit your cooling. Now if you are
thinking you can use big fan upfront to cool in worst cases you will see and
have motor running cool enough, I am all ears. BTW against popular belief according
to factory before shake up, gills do in fact evacuate air from cowl in
climb. Flying with doors prove that. also allow better cool down upon shutting
motor off.
In your case I think first is unclog the exit of the radiator by moving the oil
radiator.
As far as the water cooling goes, make something pretty temporary, this way instead
of overheating that is pretty terrible on motor, you can cool with the water
till you figure out. Same goes with rich switch, same goes for gill fans.
On a 85F day at sea level, I want to be able to take off at 115% power and climb
at best angle of climb for 30 seconds and then best rate of climb in fine Airmaster
pitch for another 3.5 minutes, then 100% power till I get to 18K near
gross and have temperatures happy. I also want to be able to taxi in 85F for longer
than I care for and not be able to take off, but have temps at a reasonably
low level. Thats is my goal.
Have ability to cool worst case, then oil thermostat to keep oil temps warm automatic,
and have reversible radiator intake duct to act as a cowl flap, constipate
amount of air flowing through.
Good luck, please keep us up to date.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=300259#300259
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| Subject: | Re: Rotax 914 Intercooler |
Hi Frans.
I did speak to John Hurst and he said he measured airbox temp and especial at altitude
it dropped with intercooler. He mentioned it dosen't work so well you
really need to worry about carb ice, but would allow one to fly to 18K without
intervention of TCU. I am only repeating what he said, I have yet to measure.
For what it's worth, my 1983 Volvo GLT-50 (245) turbo station wagon, with 2.3
liter 4 cylinder, pretty much same as 914 Garette air cooled turbo as 914, and
~ 185hp said intercooler lowered air temperature going into manifold from 145F
above ambient to only 45F above ambient. I think boosts were similar to 914??
Size of radiator was about size of coolant radiator.
Intercooler installed as per factory instructions from John do in fact lead to
further constipation of cowl air compared to not having it installed. A mono with
gear down and factory located stainless firewall has far worst exit air ability
than a Tri with firewall moved way back. None the less still not stellar
on the ground and in climb.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=300260#300260
Message 12
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| Subject: | Re: Europa - Battery cable sizing |
Just a quick note on CCA, I too have an aft mounted battery on 914 mono and am
using #4 CCA, the dameter of #4 CCA is closer to #2 Tefzel standard copper wire
than #4 Tefzel wire but the resistance is almost identical to #4 tefzel.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=300261#300261
Message 13
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| Subject: | Europa - Battery cable sizing |
Hi Kevin,
Thanks for that ........... seems a great solution!!
Kind regards
Bob
From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-ser
ver@matronics.com] On Behalf Of Kevin Klinefelter
Sent: 06 June 2010 22:28
Subject: Re: Europa-List: Europa - Battery cable sizing
Hi Bob,
the link below will show you an option that I and many others have used.T
he 4awg is serving me well in my XS mono 914
Kevin
http://www.periheliondesign.com/fatwires_files/fatwire2flyer<http://www.pe
riheliondesign.com/fatwires_files/fatwire2flyer.pdf>.pdf<http://www.perihe
liondesign.com/fatwires_files/fatwire2flyer.pdf>
----- Original Message -----
From: Bob Fairall<mailto:Bob.Fairall@fairalls.co.uk>
Sent: Sunday, June 06, 2010 1:03 PM
Subject: Europa-List: Europa - Battery cable sizing
Hi all,
Please may I have some advice on battery cable size.
My existing Europa uses 2AWG cables. In the interests of weight saving, on
my new 'XS' Mono I have started installing 4awg cable for the approx 7'6"
run. However, I'm now a little concerned that 4awg will be sufficiently h
eavy.
Many thanks in anticipation.
Bob Fairall
Kit 71 - 420 hours and going strong.
Kit 494 - getting there!!
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Message 14
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| Subject: | Combustion air inlets |
On Jun 6, 2010, at 12:38 PM, Frans Veldman wrote:
> While solving my cooling problems, I learned a few things:
> 1) Naca ducts provide no ram air, but merely "allow air to get in".
To all you 912S powered flyers,
Page 8-1 of the Europa "912 Rotax installation manual" states:
> The engine inlet air is fed through a NACA duct situated in the top
> cowling. It passes into a plenum
> chamber which feeds the air directly to the carburettors. This
> ensures that the coolest air available is
> used at all times, thus ensuring no reduction of engine performance.
If Frans is correct, it would appear to follow that the 912S plenum
does not offer inlet air to the carbs under ram air pressure.
And since the 914 engine inlet is a NACA vent also, the same would
apply.
I'm surprised...having thought that engine performance benefits when
the carb gulps air which is above ambient pressure.
Any wisdom to pass on to a heretic?
Fred
A194 (w/ Sube)
Message 15
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| Subject: | Re: Combustion air inlets |
On 06/07/2010 01:41 AM, Fred Klein wrote:
> If Frans is correct, it would appear to follow that the 912S plenum does
> not offer inlet air to the carbs under ram air pressure.
There is quite some information available on the internet about
naca-ducts, where they were designed for, and what they can and can't do.
Naca ducts were designed for applications where you want to "let air in"
without drag penalty. They harvest air from the boundary layer, the
non-moving layer of air attached to the airplane.
If you need RAM air, you need something to protrude through the boundary
layer, a sort of scoop, or a frontal inlet.
See:
http://www.flyingmag.com/scoop-naca-scoop
" ... The conclusions of the Ames group's 1945 report were upbeat, but
they included a caution that designers have been ignoring ever since.
"The submerged inlet is essentially a high inlet-velocity-ratio type in
contrast to wing-leading-edge and fuselage-nose inlets," they wrote.
This characteristic limited its most efficient use to systems "that
require only a small amount of diffusion, such as the internal ducting
for jet motors of the axial-flow type." Submerged inlets were unsuitable
for "oil coolers, radiators, or carburetors of ... reciprocating
engines," the report continued ... "
Of course, if there is anyone willing to measure the pressure inside a
naca duct against the static port (ASI ?) we know for sure. But as far
as I can see, the 912S naca inlet doesn't provide any ram effect to the
inlet air.
Frans
Message 16
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| Subject: | Re: Combustion air inlets |
On Jun 6, 2010, at 11:15 PM, Frans Veldman wrote:
> >
>
> On 06/07/2010 01:41 AM, Fred Klein wrote:
>
>> If Frans is correct, it would appear to follow that the 912S plenum
>> does
>> not offer inlet air to the carbs under ram air pressure.
>
> There is quite some information available on the internet about
> naca-ducts, where they were designed for, and what they can and
> can't do.
Frans...that's fascinating...I must find a way to remove that
conditional "if" above!
Thank you...I always assumed that designers were always looking for a
little ram-air boost...perhaps the low-drag benefit of the NACA inlet
rules over other considerations,
Fred
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