Today's Message Index:
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1. 04:36 AM - Re: Re: Carb Balancing (Bud Yerly)
2. 05:13 AM - Europa fuselage wanted (John Wighton)
3. 12:44 PM - Re: Carb Balancing (Area-51)
4. 01:45 PM - Re: Carb Balancing (rparigoris)
5. 03:38 PM - 3D Skin Files (Area-51)
6. 05:56 PM - Re: Carb Balancing (Area-51)
Message 1
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| Subject: | Re: Carb Balancing |
Sorry I missed your post,
You know, in my experience I've never had a sticking valve. Good point. In our
automotive troubleshooting that was always a well documented issue, but I've
just never had one in my Rotax. However, you bring up something that is really
important. If the valve on the dual manometer gauges is wide open, the needles
swing just like a sticking valve due to the valve timing and short intake.
Great point. To use the Rotax balancing setup, one has to close the valves
to smooth out the needle movement to get anything close to accurate. John Hurst
had an old dual manifold gauge from a multiengine plane he used for balancing
and it worked perfectly without any valve because of the small orifice in
the gauge itself for smoothing.
The choke valve is another issue I've not had because I made sure I had properly
adjusted my linkage cables. I've also never had a leaking starting carb gasket.
I did find out from testing the carbs run lean above about 4000 if the
choke cables are pulled.
I know that the pistons in the Bings, when out of sync, will be a bugger to find
with only a vacuum gauge set. I went nuts trying to figure out my slight roughness
problem about 15 years ago. I made up that plumbers piece to test and
finally found the issue in my plane. I tried cleaning up the walls and pistons,
new diaphragms, and such to no avail. Lockwood advised that I needed two
new carbs. Later when talking to the Rotax factory reps, I was advised that
they actually match their sets of Bing carbs to ensure this was not a problem
with a new engine. I broke down and bought two new matched carbs and it has been
fine ever since. I know a couple of owners that only changed one carb and
it balanced fine. Were they lucky, or is there a wear issue in the Bings we
don't know about?
I hope one day one of you guys stumbles on how to repair/adjust a set of carbs
that fail to work in unison because of bad pistons. Changing out diaphragms and
gaskets, cleaning and smoothing didn't work for me. Is it geometry, weight,
passages, clearances or what is the actual cause, and what solution is needed
to ensure the carb pistons work in unison has surely escaped me. I never did
figure it out. I threw money at it after nearly six months of tinkering and
my two new carbs worked on the bench in unison and were smooth running.
All one can do is check the compressions are all consistent so you know the mechanical
is sound, then on to the carbs, to ensure they are rebuilt and work in
unison and then on to the ignition.
You know, it is always the last thing you check that finds the issue. Or you can
do the car dealer repair method, just change components until the engine runs
right and charge the customer.
Thank you for that,
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matronics.com>
On Behalf Of Area-51
Sent: Sunday, September 19, 2021 8:55 AM
Subject: Europa-List: Re: Carb Balancing
Thanks for the pdf write up Bud; its very thorough informative and extensive, and
yes will save many going through all those experiences to find a solution...
On the issue of this thread, have you used a dual meter to observe left/right manifold
pressure readings through operating rpm range and while the vibration
at 3500rpm is active, flickering needle on either gauge will indicate sticking
valve; theres also small chance one of the choke valves is not fully returning
to correct position, or a carburettor piston may be binding intermittently on
the slide... then again it may not be fuel/carbi related.. if you have access
to two verified good carbis then swap them out and see if the issue disappears...
will be interesting to see what it ends up being !!
Read this topic online here:
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fforums.matronics.com%2Fviewtopic.php%3Fp%3D503218%23503218&data=04%7C01%7C%7C04d95dde710a4934669308d97b6d600a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637676531975449608%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=j67EJzlVmMeoyK22LbZObvI5A21n2%2Fe%2Bi31azVmByS8%3D&reserved=0
Message 2
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| Subject: | Europa fuselage wanted |
Wanted
The damaged or scrapped fuselage of a Europa. We are creating a static demonstration
of the Acroflight TD Mod and need a damaged or unairworthy fuselage to
work on.
Anything considered but ideally will be forward fuselage/canopy. We intend to
cut the fuselage down to make it transportable by trailer.
The TD Mod consists of main legs, sockets, metallic cross-tubes, web filled with
ply/foam, wrapped in GF plies. We intend to show one side finished (but un-trimmed)
and the other side partially completed (naked construction).
We can collect it anywhere in the UK.
--------
John Wighton
Europa XS trigear G-IPOD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503233#503233
Message 3
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| Subject: | Re: Carb Balancing |
I hear you there Bud... getting the dual vacum gauge to function may require blocking
off the balance pipe between left/right manifolds, otherwise backpressure
may interfere with true gauge reading; inline restrictor would dampen needle
movement.
The bing carbi is not too different to the stromberg; age/grime/carbon blowing
back into the inlet manifold from the combustion cylinder will eventually result
in wear between carbi piston and its bore; so over time there would be slight
discrepancies between operational height at various rpm due to slight vacum
differences ; so the more carburettors used the greater the opportunity toward
variation in mixture; and the way each carbi is balanced off against the others
is by raising each piston manually and observing changes at idle or set rpm
(as with SU or Stromberg tuning)... It doesnt take much to setup a minor harmonic
vibration. This is why a dellorto can offer superior performance; from dellorto
its onto the world of mechanical or electronic injection and all have
their endemic nuances.
Another usable diagnostic is monitoring all individual exhaust headers at tuned
lengths from the exhaust valve; compare and contrast...
Personally, to get multiple constant depression carbis to run in perfect unison,
other than buying s new matched pair, everything needs to be set up equaly on
a bench down to .0005 accuracy, all pistons need to be checked and equally balanced,
and then piston heights need to be equally set at a uniform air flow,
and then it all needs to be setup for smooth idling... It can literally take
weeks; and you might get 200, or 2000, hours of joy... somewhere you just need
to draw the line at Cost/Time/Benefit. After 40 years making internal combustion
engines run smooth first thing I would do is throw both carbis in the bin,
unless you are a diehard purist, and fit good quality injection.
All things equal the rotax is a really really sweet powerplant which has left me
very very impressed by... as is, could probably benefit by having an O2 sensor
and readout retro fitted for inflight diagnostic.
And Bud is right there; get your fuel supply done and move onto ignition
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503235#503235
Message 4
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| Subject: | Re: Carb Balancing |
Hi Area 51 I added a mixture monitor with O2 sensor on 914 with a mixture control.
Not yet flying:
https://1drv.ms/u/s!Ah1S270Nwg9V5VC2OuaYiCuGYBtz
https://1drv.ms/u/s!Ah1S270Nwg9V5WTC-lrqsfXAr8mm
Dial controls a needle valve that leaks float bowl pressure to balance tube. Rich
switch energizes enrichment solenoid and takes my leaning circuit out of picture,
it has a diode to isolate the TCU from getting back fed.
Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503236#503236
Message 5
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I was told recently there are 3D skin files available of the europa so Xplane models
can be created.
Does anyone in the community have these files to share?
Thanks in advance!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503237#503237
Message 6
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| Subject: | Re: Carb Balancing |
Thats an intelligent and novel idea!!
Sometimes the piston spring can be swapped out for different tensions to affect
mixture under acceleration at different altitudes; other times the needle profile
can be changed to affect mixture settings at specific engine loads or rpm;
its not uncommon to see some really old guy playing with a watchmakers lathe
doctoring the factory OEM needle to perfection...
Get a copy of Phil Irvings book tuning for speed its the standard bible of engine
tuning...
At the end of the day inlet manifold pressure, exhaust header temperature and oil
pressure, an attentive ear and backside is all you need to monitor a motor;
everything else is ancillary and a bonus!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503238#503238
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