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1. 08:32 AM - Re: Re: What did you do with your Europa this week - 18/11/22 (Bud Yerly)
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| Subject: | Re: What did you do with your Europa this week - 18/11/22 |
I agree whole heartedly.
Those of us that have learned how to tune comes down to our power of observation,
but also inspections. We look at the engine smoothness (from idle to full),
plugs, exhaust tip color, temperatures, and find at the power range we run in
it doesn't matter whether it is carbureted or injected. Now fixed timing is
a bit of a problem in aircraft engines but if timing is optimized to the engine
power band, performance is similar in the long run between the two. As for
a FART being necessary, it is a nice tool, but not essential. I don't have one
as my wife doesn't like me to play "pull my finger" with the grand kids.
The biggest issue we have in Florida is these lean on the ground 912iS and 915
can't get to the end of the runway without overheating. If you want to run lean
at all times you need a much larger cooling system, fans and ducting. I have
found the latest 914 intake and carb jetting runs a bit richer than the original,
but the new one does run cooler and smoother. I'm OK with a slightly rich
mixture, as stated, a turbo boosted engine can go bad fast if there is an
air leak, or a leaning carb. In my plane I burn about a tenth of a gallon more
per hour on average. If I'm worried about a quart of fuel over a long leg,
I needed to plan better.
Guys think I am crazy for doing a 25 hour inspection on the engine. Carb leaks,
fuel staining, and top plug inspections can be done while the oil drains.
If the two EGTs, CHTs, oil temp and pressure are like it was in my logs, I leave
it alone. If there is a change, I look and test. My oil pressure gauge was
an issue this year. It was reading lower than originally installed:
During my hose change (8 years and the R7 or better are still good but the clamping
areas tended to look a bit too tight, so I yanked them all) I just did a
calibration on all my instruments. It took an hour. I have had to install a
15-ohm resistor on my new oil pressure sensor to adjust the offset and improve
the gauge reading. CHTs are pretty good still, measured with my Harbor Freight
temp sensor. I swapped out an EGT probe that was going bad, (plugs looked
great) took out my torch and compared the now mismatched set (one Westach and
the other off the shelf something I had) and two probes were equal enough (OK
at 900F and off <50F at 1400 F so I got lucky). On my website I have how I do
all that testing and calibrate the gauges. Yes, I still have round dials as
installed in 2005 in my panel as I used gauges from another Europa getting an
EIS upgrade. Right off the shelf I found all of them fairly accurate when I
tested them. My original oil sensor was replaced this year (10 years old), and
pressures back then were 10 PSI low across the board and I just memorized that.
Now it is 2022, and the oil sensor is being replaced and a new one installed
on the firewall (I hate adding weight, but it is a test) The new sender and
gauge now needs a 15 ohm resistor to read nearly spot on from 10 to 100 PSI.
Learn your engine. Educate yourself, ask questions and be a disciplined observer.
I never trust a gauge reading only (look for symptoms, test and verify).
Look at your engine during the oil changes or at a 25 hour. Those of you trying
to extend your oil change (some to 100 hours) look at your oil closely. If
it doesn't look like new when running unleaded gas, change it (even 50 hours
is a bit long for me). (100LL grays up fairly soon, so a 25 hour oil change
is sensible.) The smallest impurities are not always picked up by the oil filter.
The solution is not a finer oil filter, as that affects pressure and bearing
bathing, the solution is don't be cheap, change the oil. That rids the blow
by debris, turbo carbon and water contamination from the engine the fastest.
Spend the $60 and inspect the engine for potential issues and catch and fix
issues early.
Now back to the shop to replumb my fuel system and a couple of upgrades to old
N12AY.
Just my thoughts,
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matronics.com>
On Behalf Of Area-51
Sent: Friday, November 18, 2022 12:31 AM
Subject: Europa-List: Re: What did you do with your Europa this week - 18/11/22
Hi Ron,
The FART is smelling Oxygen.. whether its CO1 or CO2 is irrelevant to me; i just
want the FART to tell me how much Oxygen it is smelling; if the FART says 14.5
then i know its a happy FART. As long as my FART is happy i am happy also...
Whether the mixture is observed to be slightly rich during taxi, couldn't care
less; its 5-10 minutes of mild operational demand time.
You cannot leak boost pressure back through the float needles on a 914 snd expect
to keep moving; firstly that would intimate that your boost pressure is higher
than your fuel pressure; secondly you would run out of fuel on one or both
carburettors.
The float chambers need to remain equalised to plenum pressure; if they are leaking
air pressure the engine will run lean; hence all the Rotax instructions;
and yes you tune to the leanest cylinder always; using an infrared pistol tester
is good enough to indicate this.
Remember you have a lot less room to get it wrong with turbo charging; things go
crunch a lot quicker with less warning. If you want to run really lean above
50% power as you mention then firstly you are already going to be at 30% power;
so you will give it more throttle; then you will experience more heat, and
its all down hill from this point.
Its like performing an engine out glide approach; the airframe has its optimum
airspeed for endurance and distance... 14.5 Stoich is that optimum Oxygen content
for "all" petrol engines under "all" operating conditions, for maximum thermal
efficiency, end of story...
There are numerous ways to diagnose and monitor engine tune; for me its pretty
much field experience knowing the different harmonic tones generated by different
engine cylinder formations under full and partial load; they indicate air/mixture,
spark timing, or mechanical imbalances. The FART is purely a final quality
assurance confirmation for me befor signing off on maintenance service.
There are endless test points that can be used to monitor an engine; Oil Pressure
and Head Temp are the most vital, the rest are nice to haves but not essential
and are just early warning meters for the less experienced. If you want perfect
analogue economy as good as any fuel injection device then you want to know
your manifold pressure and exhaust oxygen content, and maybe add as a cross
reference exhaust temperature probe, however to be as accurate as the O2 sensor
the EGT probe really should be placed right at the valve throat; so for a
912/914 that's 4 probes.
For a 914 the best point to probe EGT is upstream at the impeller, this area between
the head and impeller is by default a fairly constant temp environment and
will rise and fall according to boost load and is a cross reference point for
oil and head temperature meters, the other point i would probe is inlet air
temp post intercooler, but personally i would still really on my O2 readings
as a final checkpoint.
All this above will give the operator the insight that the engine, mixture wise,
can or cannot run any better than is being indicated.
Read this topic online here:
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