Apparently, my photos were too large. OOPS! Here is a reprint of my email
from this morning minus photos that are in the word attachment.
Bud Yerly
________________________________
From: Bud Yerly <budyerly@msn.com>
Sent: Wednesday, August 21, 2024 9:46 AM
Subject: Re: Europa-List: Re: Rotax 912ULS oil consumption
I agree with Jim and have written on this in my techniques paper on Rotax T
roubleshooting.
I was emailing back and forth with Ron Paragoris, who is nearing engine run
and finding that drip, drip, drip, out of the turbo.
Oil in the 914 will always slowly drain from the oil pump, into the return
line of the turbo (which has no check valve) and after a few weeks to a mon
th fill the turbo can, inlet, air filter, muffler, etc. with a small but a
nnoying amount of oil.
If your Rotax drops below about 76/80 on a differential compression check g
et a top overhaul accomplished. It mainly will need the valves cleaned up.
I do a full gearbox rebuild between 500 and 600 hours. Why not pull the
cylinders and clean up the heads at the same time. My 500-hour engine now
is at nearly 80/80 and the compression on my 914 feels like a 912S. It bur
ps in only =BD the number of blades. I burp a second time from habit, and
my oil level is about =BE to half way up the new dip stick which is normal
for my particular engine and tank height.
I don't normally re-burp after a flight to check the oil level unless I am
just checking my fill level on cross country. My old 914 has always pushed
out about =BC of a pint (0.25L) after about 10 hours. Then it pretty much
stays there. by the 20-30 hours of my annual flying I see only a =BD lite
r lost per oil change.
The oil mess of the 914 is through the turbo. I rarely see much oil coming
out of my oil tank vent tube. I installed a drip can on my oil vent and h
ave monitored the oil out of my vent tube and it amounts to about 2 oz. in
about 20 hours (yea that's all I fly per year now). The 912 and 912S in my
opinion are free of turbo drips. So, the only loss should be through the
rings, valves and the oil vent line. Do not underestimate the amount of su
ction on the oil vent line issue. The vent should be done IAW the Rotax in
stallation manual to prevent continuous suction out the vent line. The vap
or contains water and oil, and you will note oil on the belly coming out of
the vent if it is sucking oil out. Plus an improperly made oil vent line
may lower the ability of the engine to return oil to the tank.
I'm including some of what Ron and I discussed and a paper on my oil drip c
ans. (Drip cans can be more of a pain than they are worth.)
Questions have ** and the answers follow:
** If the engine isn't turned over since I removed 3/4oz of oil from the tu
rbo, will it refill and leak out through the air cleaner again?
It has been my experience that yes it will drip down into your can under th
e turbo mostly through the oil return line! Most of us make or made sure t
he feed check ball valve to the turbo is clean and operating but there isn'
t anything we can do about the oil seeping out between the pump gears back
into the oil drain line from the turbo which is the lowest point of the eng
ine. The oil seep is about 5-15cc per week in my experience. This drippin
g through the oil pump fills the cold turbo seal, and runs out the turbo in
let and exhaust side. The oil fills the air filter but frankly is harmless
and eventually makes a mess of your cowl.
On start up, if the oil is not sucked out after setting a month, will be fl
ung up into the plenum and get burned in the cylinders. I don't normally s
ee a problem with this to the carb performance but the plugs do sometimes g
et oil soaked. Especially if the plugs are old or if were mechanically cle
aned. Plugs need a good sharp point to form the jump between the electrode
and ground bar. The edges on the older plug tend to round out. The good n
ews is it affects the lower plugs more than the upper so starts are normall
y not seriously affected in the 914.
On startup, the oil in the exhaust will cover the left gear, wing root and
belly. Messy, but harmless.
** When flying, can you start the motor with oil filling the turbo and leak
ing out the air cleaner?
When flying you will have no issue with restarting.
** If your answer is that it's not a good idea to start with oil leaking ou
t the air cleaner, do you recommend cleaning the air cleaner? How to clean
it?: Real clean job of using air cleaner cleaning solution and then oil wit
h air cleaner oil? Or perhaps wrap with paper towels and blot out most of t
he excess oil?
If the plane has sat for a few weeks or a month, I tend just start it up.
Some oil gets spattered out of the exhaust, and the lower plugs will get oi
l soaked. I run the engine up after run up and burn off the oil from the p
lugs. It is not uncommon to see a 500 RPM mag drop, from oil soaked plugs
so simply running it up to max continuous power for a minute disturbs the n
eighbors but cleans the plugs off enough to get about a 300 RPM drop.
** After a flight, on a normal 914 that has a pretty good sealing turbo oil
check valve, how long sitting will usually have oil coming out of the air
cleaner?
I think that was answered above.
** Have you devised a way of draining oil from the turbo without having to
remove the cowl?
I have made an experimental oil catch for my air filter. It prevents some
of the oil from soaking the oil filter paper. I think most use K&N filters
but a cheap Fram may be as good and just throw it away. I use the 20 degr
ee bend filter and just clean it with every other oil change and or annuall
y because I don't fly that much any longer.
What a pain to make and ensure that it won't get sucked into the turbo. It
is just a plate that contacts the lip of the turbo inlet then has a depres
sion for the oil to settle in. It works OK so far. Oil does drain down an
d out through a tube. If the oil puddle builds up under the engine, then i
t is probably prudent to suck the oil out of the turbo. Or just start up,
run the engine, then go to the wash rack and wash off the oil spatter on th
e aircraft belly, gear and wing. Good news for the mono is the brake is on
the opposite side of the tire from the exhaust.
For the 912/912S guys you can see this turbo issue is not an issue you must
contend with. However, you have another issue that water can enter your a
ir filter plenum and fill your manifold, float bowls and engine cylinders i
f the plane is setting outside in the rain. Any valve that is open in the
cylinder will allow water to enter the cylinder. It will create mold in yo
ur plenum bottom and make a mess. This is very true of the trigear. Keep
your drain holes clear, and I written on how I avoid the rain getting in th
rough the inlet. It will save engine internal corrosion and many problems.
Keep your pretty airplane in a hangar or purchase a cockpit and engine co
ver if you must have an outside tie down.
If your 912 is using oil, consider a top overhaul on your 912 and check you
r lifters. Clean up the valves (lapping) check the rings and your lifters.
If they are fine, don't fool with them. Watch your vent line draft. Tha
t renewal of your valve seats can be a game changer. It doesn't matter if
you use unleaded, ethanol laced or 100LL fuel, valves get dirty and compres
sion and power will suffer.
Best Regards to all,
Bud Yerly
Custom Flight Creations, Inc.
________________________________
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matr
onics.com> on behalf of h&jeuropa <butcher43@att.net>
Sent: Tuesday, August 20, 2024 10:03 PM
Subject: Europa-List: Re: Rotax 912ULS oil consumption
I have a different view on the oil check burping.
According to the Rotax Operators Manual,
1. Remove bayonet cap from the oil tank, turn the propeller
slowly by hand in direction of engine rotation several
times to pump residual oil from the engine into the oil
tank.
2 It is essential to build up compression in the combustion
chamber. Maintain the pressure for a few seconds to let
the gas flow via the piston rings into the crankcase. The
speed of rotation is not important but rather the continuous
pressure and the amount of gas which is transferred
into the crankcase.
3 This process is finished when air is returning back to the
oil tank and can be noticed by an audible gurgle from
the open oil tank.
4 Check oil level and add oil if necessary.
My understanding is that over time oil siphons from the tank back to the cr
ankcase after the engine is shut down. "Burping" the engine uses compressi
on to force the oil in the crankcase back into the tank.
We operated our 914 for nearly 1300 hours until the compression in several
cylinders got low enough that the engine no longer performed well. They we
re around 60/80 psi with a differential test and 85 psi with a conventional
test.
For the last several years we were unable to get the engine to burp prior t
o start, even rotating it 50 or 60 revolutions! We quit trying and instead
when shutting down the engine, we checked the oil immediately since the ta
nk was full and the siphoning had not yet started.
Our new 914 burps after just a few turns and the compression is much higher
, it's difficult to rotate.
Notice that Rotax says to rotate slowly and to maintain the pressure to let
the gas flow. That's exactly how we do it. You can feel the pressure dro
p and hear the air flowing.
I'm surprised that burping after the last flight of the day and then checki
ng the oil level the next day gives a satisfactory result. I'd think the o
il would siphon back to the sump during that time.
Just my thoughts and experience.
Jim Butcher
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