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jbhart(at)onlyinternet.ne
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 Posted: Thu Nov 06, 2008 3:57 pm Post subject: Econo Miser!! |
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FireFlyer's & Kolbers,
I have updated the page describing the air/fuel ratio adjuster. The weather
has been very nice and so I was able to gather much more data.
I had to removed the static pressure tap from the bottom of the carburetor.
With the carburetor just about a foot in front of the propeller, a lot of
weird stuff happens. I could not get enough pressure difference to provide
sufficient control range and the system was unstable. I tried changing main
jets, etc., but it did not help. I moved the static pressure reference
point to under the wing and everything improved.
At this time, I will be cleaning up the system. To save weight, it will be
re plumbed with thin wall hard tubing and one float bowl vent will be
plugged. If you would like to see the latest data, it can be found on the
bottom of:
http://www.thirdshift.com/jack/firefly/firefly146.html
This has been very encouraging. My initial goal was be able to fly at less
than two gph, and at this point, it looks like 1.5 gph or less is a strong
possibility.
Fly Safe!
Jack B. Hart FF004
Winchester, IN
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jbhart(at)onlyinternet.ne
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| Posted: Fri Nov 07, 2008 6:08 am Post subject: Econo Miser!! |
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FireFlyer's & Kolbers,
One thing I failed to mention. With the needle raised 1/2 slot above the
normal winter position, the system can raise the EGT at least 150 degrees F.
On the last test flight it required 3.0 inches of water vacuum to bring the
EGT up to the desired temperature.
Jack B. Hart FF004
Winchester, IN
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jbhart(at)onlyinternet.ne
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| Posted: Sat Nov 08, 2008 5:54 pm Post subject: Econo Miser!! |
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FireFlyer's & Kolbers,
The weather has turned so there is no flying. Computed the change in
average fuel flows for flights before and after addition of the air fuel
mixture control and keeping the EGT constant. At today's fuel prices
($2.00) it saves about 50 cents per hour.
I added the following to the web site page today.
...........................................
Update - 11/08/08 - Fuel Savings
To check air fuel ratio control system effectiveness, I totaled the air time
and fuel used beginning with the very first system test flight. The total
system air time was 13 hours and 23 minutes, and the total fuel burned was
27.17 gallons. This computes out to 2.03 gph over 25 flights. Next I went
back in air time approximately 13 hours and 23 minutes before installing the
system and found there were 35 flights in this period totaling 13 hours, 46
minutes that burned 33.20 gallons. Since there were 10 additional flights,
10 x 0.05 = 0.5 gallons were subtracted from the total to compensate for the
extra ten engine starts and warm-ups etc. Using this new number (32.70
gallons) the uncontrolled air fuel mixture flights burn rate was 2.38 gph.
By addition of the air fuel mixture control, Victor 1+ is burning 0.25 gph
less for an eleven percent improvement in fuel economy.
...........................................
Jack B. Hart FF004
Winchester, IN
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Nov 11, 2008 9:13 pm Post subject: Econo Miser!! |
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> By addition of the air fuel mixture control, Victor 1+ is burning 0.25
gph
| Quote: | less for an eleven percent improvement in fuel economy.
............................................
Jack B. Hart FF004
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Jack H:
You forgot to brief us on performance before and after.
john h
mkIII
Nellis AFB, NV
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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jbhart(at)onlyinternet.ne
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| Posted: Wed Nov 12, 2008 7:21 am Post subject: Econo Miser!! |
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At 09:13 PM 11/11/08 -0800, you wrote:
| Quote: |
You forgot to brief us on performance before and after.
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John,
I thought I did. The average fuel flow rate after mounting the system was
2.03 gph. The average fuel flow rate before mounting the system over the
same total time period was 2.38 gph. Since I could not subtract correctly,
I will give the corrected difference in that the system has reduced the
average flow rate by 0.35 gph for a 15% reduction in flow rate with the
system. This indicates that for every three hours flown, I get a half hour
flight for free.
If you are talking about flight performance, at this time there is no
change. With the leaning, the engine picks up some rpm and so I could crank
a little more pitch into the IVO. At this point, I would rather leave the
pitch alone and take some more fuel flow data at lower and higher EGT's to
see what effect it would have on the fuel flow rate. I was lucky to get as
much data as I did for the time of the year. So I may not be able to
complete the data taking until next year.
One of the things I discovered from trying to develop a good static pressure
source, is that on a pusher with the carburetor very close in front of the
propeller, in my case about one foot, engine performance is degraded. This
is due to the fact that the propeller is accelerating (sucking) the air and
in doing so causes a local pressure drop. I discovered this when I tried to
place a static pressure tap on the bottom of the carburetor. Also, I
discovered that with the pressure was very unstable. A change in direction
could cause a change in pressure. I believe this was caused by the engine
profile blanking the propeller entrance air flow relative as one crabbed
into the wind. By moving the reference point below the wing all of this
variation went away.
There are several things, I don't understand. One is that with the EGT
elevated and at cruise rpm, I can push the stick forward, and raise the rpm
200 rpm without the EGT increasing. Or I can power down at 500 fpm and
reduce the throttle a little to maintain constant rpm and the EGT does on
increase. This makes it very nice for approaching an airport, as I do not
have to slow up to loose altitude. There is some kind of interaction within
the system that makes it some what self compensating.
Cold out side and no flying so I am rambling.
Fly Safe!
Jack B. Hart FF004
Winchester,
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Wed Nov 12, 2008 7:49 am Post subject: Econo Miser!! |
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>
| Quote: | There are several things, I don't understand. One is that with the EGT
elevated and at cruise rpm, I can push the stick forward, and raise the
rpm
200 rpm without the EGT increasing. Or I can power down at 500 fpm and
reduce the throttle a little to maintain constant rpm and the EGT does on
increase. This makes it very nice for approaching an airport, as I do not
have to slow up to loose altitude. There is some kind of interaction
within
the system that makes it some what self compensating.
Cold out side and no flying so I am rambling.
Fly Safe!
Jack B. Hart FF004
Winchester,
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Jack H:
Very interesting. Certainly not a normal reaction for a two stroke aircraft
engine.
When I started flying my newly built Kolb Ultrastar in 1984, I had no
experience flying with a two stroke. I flew almost every day back then.
Most flights were filled with experiments. On one particular flight I
noticed the two stroke seemed to make large rpm changes when loaded and
unloaded, maintaining constant throttle at cruise rpm. Push the nose over
and the rpm would rapidly increase. Pull the stick back and rpm would be
rapidly reduced. I also noticed EGT changes during these maneuvers. Unload
the engine, egt climbed. Load the engine, egt dropped. Wow! I had never
read this info in any of the magazines and books that were available about
Ultralights. About this time I discovered our airplanes should be propped
using same technique as propping a boat. WOT, straight and level flight,
bump the red line. Of course, this worked with non-inflight adjustable
props. I also learned, in most cases, Rotax and Cuyuna engines were tuned
correctly when they left the factory. Propping the engine/aircraft combo
correctly would put all engine temps, EGT/CHT, in the green. It was not
necessary to change jets and spark plug heat ranges when based up to 1500
feet ASL with operating temps 40 to well over 100F. That was 24 years ago.
I think that system still holds true today. I still prop my engines, 912
series now, WOT, straight and level flight, just bump the red line, the
same way.
john h
mkIII
Las Vegas, NV
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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