M20 Air/Oil separator

Condensation and the sludge buildup that
would result was my main concern since the M20
is not dis-assembleable for cleaning like the
Walker/Air Wolf unit. At each annual I soak it in
AvGas and then blow it out with compressed air.

I can understand condensation, but sludge?

With regular flying, and scheduled oil and filter changes, what is the
source of sludge in an M20? Combustion bi-products?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

If you put too much oil in an engine it will heat up the engine more
because the crankshaft hits the extra oil and causes the oil to be
flung around and this also leads to oil foaming.
Extra heat is generated by flinging the oil around and the bearings
don't get enough oil since the pump does not pump foam well.

A oil quality gauge would be nice but it would add weight and cost. A
simple float switch set at 4 quarts would be nice and should not cost
much?

The old radial's used to have oil tanks that held 5 or 10 GALLONS.

If you really want to know how much water is returned to your engine
by the M20 route the oil return to a quart catch bucket for a few
hours. Then look at the contents of the bucket. One good test is
worth a thousand expert opinions!

I have found over the years that my O320 likes to run at 7 quarts. If
you fill to the max 8 quarts it uses that 8th quart in about 2 hours.
I did discover an interesting effect last month. I normally use a
quart in 4 to 5 hours. By flying at 8000 to 14000 feet for 41 hours
on a trip I only used 2 quarts in 41 hours. Since I was running wide
open throttle I had no engine manifold vacuum most of the time. It
would appear to me that the extra oil usage at part throttle was
caused by the oil being sucked down the intake valve guides.
Someone more knowledgeable may comment on this.

On Sun, 15 Aug 2004 02:44:50 GMT, "Jay Honeck"
wrote:

Air/Oil Separators do seem to perform their intended function with a
minimum of problems (when installed correctly, anyway), but my mechanic
recommended I NOT install one because they return moisture to the case
that would normally be vented overboard with the oil vapor. The
long-term effect is reportedly the same as if you were to run the engine
for short periods without attaining the operating temperature required
to boil off the water -- namely, corrosion.

Thanks for the comments, Doug. I had not heard this, and my mechanic did not
mention it, but I suppose it makes some sense.

On the other hand, since I fly every few days, I find it hard to imagine
that moisture could build up (or even survive) a flight with CHTs in the 350
degree range, and EGTs in the 1500 degree range!

There is also something to be said, IMHO, for adding oil between oil
changes. Oil breaks down over time, and throwing in a quart every 5-10
hours replenishes the anti-wear/anti-corrosion additives as well as
increases the oil's natural ability to hold contaminants in suspension.

Well, I change my oil around 25 hours minimum, 50 hours maximum. Hopefully
the billion-dollar-a-quart semi-synthetic Aeroshell oil holds together at
least THAT long before breaking down?

Also, I have found no hard evidence that keeping the oil topped vs. 1 or
2 quarts down provides any additional cooling or anti-wear properties.

I have no hard evidence either, but since oil flow is an important part of
cooling an air-cooled engine, I have to believe that having 50% more oil in
the engine is going to improve cooling performance. It also follows that
having 50% more "clean" oil flushing through the engine should keep
everything internal just that much shinier?

This is no surprise, really, as the O-360 certainly doesn't *need* six
or eight quarts of oil. I know of one application (the Seminole) in
which it is certified to run on as little as 2 quarts.

Well, yes and no. While Lycoming SAYS it's okay to run them down to 2
quarts (or even less), it is nevertheless true that engine cooling will be
hurt by low oil quantities. Sometimes less is more; in this case, only
more is more.

As an adjunct to this discussion, you've got to wonder why aircraft engines
are designed so that in the event of a leak you won't know you're out of oil
until the last pint drains out.

The oil gauge on our engines reads pressure -- not oil capacity. As a
result, you can have a major oil leak and you will not know it until those
last few ounces vent overboard -- and THEN your oil pressure gauge drops to
zero. We recently had a local Skyhawk pilot lose an oil line in flight, and
he did not know he was in trouble until his oil pressure gauge finally
dropped to zero -- at which point the crankcase was already empty, and he
was frying his engine. (He made it to an airport, but destroyed the
engine.)

What baffles me is that no one has come up with an oil QUANTITY gauge like I
have in my Mustang. This would have given the aforementioned pilot an extra
five or ten minutes to get that plane down, BEFORE he had ruined a $16K
engine.

Anyone know?

Lastly, FWIW, my partner's other airplane (a 182) has a M20 installed.
Yes, its belly is largely free of oil residue, but it still seems to
acquire a dry, chaulky residue in any case. It looks and feels like
something you'd find just aft of an exhaust stack, and may very well
result from the exhaust...

Oh, I'm sure I'll have some exhaust stains to clean -- but at least I
(hopefully) won't have that slimy belly (with dirt and grass embedded in it)
to clean off.

On Sun, 15 Aug 2004 02:44:50 GMT, "Jay Honeck"
wrote:

Air/Oil Separators do seem to perform their intended function with a
minimum of problems (when installed correctly, anyway), but my mechanic
recommended I NOT install one because they return moisture to the case
that would normally be vented overboard with the oil vapor. The

I think part of this is "old wives tales" as the ABS mechanic
recomended it, my mechanic did, and there are quite a few in service
around the airport.

long-term effect is reportedly the same as if you were to run the engine
for short periods without attaining the operating temperature required
to boil off the water -- namely, corrosion.

At the end of 20 hours my oild is still clean. Not haveing a filter I
change at 25 hours. In a thousand hours of operation I've only added
oil twice. Normally it is down less than a pint at 25 hours.


Thanks for the comments, Doug. I had not heard this, and my mechanic did not
mention it, but I suppose it makes some sense.

On the other hand, since I fly every few days, I find it hard to imagine
that moisture could build up (or even survive) a flight with CHTs in the 350
degree range, and EGTs in the 1500 degree range!

I've had no moisture problem with mine and the air/oild seperator was
put on long before I purchased the plane.

I use straight aeroshel 100 50 weight in summer and 30 in winter.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

There is also something to be said, IMHO, for adding oil between oil
changes. Oil breaks down over time, and throwing in a quart every 5-10
hours replenishes the anti-wear/anti-corrosion additives as well as
increases the oil's natural ability to hold contaminants in suspension.

Well, I change my oil around 25 hours minimum, 50 hours maximum. Hopefully
the billion-dollar-a-quart semi-synthetic Aeroshell oil holds together at
least THAT long before breaking down?

Also, I have found no hard evidence that keeping the oil topped vs. 1 or
2 quarts down provides any additional cooling or anti-wear properties.

I have no hard evidence either, but since oil flow is an important part of
cooling an air-cooled engine, I have to believe that having 50% more oil in
the engine is going to improve cooling performance. It also follows that
having 50% more "clean" oil flushing through the engine should keep
everything internal just that much shinier?

This is no surprise, really, as the O-360 certainly doesn't *need* six
or eight quarts of oil. I know of one application (the Seminole) in
which it is certified to run on as little as 2 quarts.

Well, yes and no. While Lycoming SAYS it's okay to run them down to 2
quarts (or even less), it is nevertheless true that engine cooling will be
hurt by low oil quantities. Sometimes less is more; in this case, only
more is more.

As an adjunct to this discussion, you've got to wonder why aircraft engines
are designed so that in the event of a leak you won't know you're out of oil
until the last pint drains out.

The oil gauge on our engines reads pressure -- not oil capacity. As a
result, you can have a major oil leak and you will not know it until those
last few ounces vent overboard -- and THEN your oil pressure gauge drops to
zero. We recently had a local Skyhawk pilot lose an oil line in flight, and
he did not know he was in trouble until his oil pressure gauge finally
dropped to zero -- at which point the crankcase was already empty, and he
was frying his engine. (He made it to an airport, but destroyed the
engine.)

What baffles me is that no one has come up with an oil QUANTITY gauge like I
have in my Mustang. This would have given the aforementioned pilot an extra
five or ten minutes to get that plane down, BEFORE he had ruined a $16K
engine.

Anyone know?

Lastly, FWIW, my partner's other airplane (a 182) has a M20 installed.
Yes, its belly is largely free of oil residue, but it still seems to
acquire a dry, chaulky residue in any case. It looks and feels like
something you'd find just aft of an exhaust stack, and may very well
result from the exhaust...

Oh, I'm sure I'll have some exhaust stains to clean -- but at least I
(hopefully) won't have that slimy belly (with dirt and grass embedded in it)
to clean off.

"Jay Honeck" wrote in message news:OaATc.292632$JR4.125853@attbi_s54...

I can understand condensation, but sludge?

With regular flying, and scheduled oil and filter changes, what is the
source of sludge in an M20? Combustion bi-products?

Well they say that cars driven a short distance suffer from sludge
buildup
when the acidic moisture, created as a combustion by-product, remains
in the oil. I believe the same is true in an aircraft engine. Any
place
where entrapped moisture routinely remains in contact with oil will
form
sludge. Look at the vent tube on an airplane with considerable time
on
the engine. Some have sludge build up because they cool the crankcase
vented gases low enough for the moisture to condense out and remain
on the inside walls along with a film of expelled engine oil.
Depending on
where an air/oil seperator is located it too can run cold enough to
become a collector of moisture and therefore suffer from sludge
buildup over time.

My M-20 is located high enough and out of the engine cooling airstream
to
get and stay relatively hot. Since I can't visually inspect my M-20 I
take the proactive measure of cleaning it out each year.
In fact if my memory serves me correctly I believe the instructions
for
continued airworthiness on the M-20 STC says to clean it periodically.

GaryP

More oil does not improve cooling. If you think about it, it makes sense.
Where would the additoinal heat go? Same oil cooler, same cooling fins,
same baffles producing the same airflow. The oil will actually be hotter
since the crank is going to contact the oil in the sump with 50% more oil.
Thats why the top 4 qts of oil is leaving through the breather in the first
place.

The oil will be somewhat cleaner since the same amount of contaminates are
dilluted by more oil. As a practical matter, you would probably be better
off with a finer oil filter than more oil. There is an article on oil
filters in Aviation Consumer this month that is worth reading.

Mike
MU-2
Helio Courier (arriving today!)


"Jay Honeck" wrote in message
news:C6ATc.312310$XM6.196374@attbi_s53...
Air/Oil Separators do seem to perform their intended function with a
minimum of problems (when installed correctly, anyway), but my mechanic
recommended I NOT install one because they return moisture to the case
that would normally be vented overboard with the oil vapor. The
long-term effect is reportedly the same as if you were to run the engine
for short periods without attaining the operating temperature required
to boil off the water -- namely, corrosion.

Thanks for the comments, Doug. I had not heard this, and my mechanic did
not
mention it, but I suppose it makes some sense.

On the other hand, since I fly every few days, I find it hard to imagine
that moisture could build up (or even survive) a flight with CHTs in the
350
degree range, and EGTs in the 1500 degree range!

There is also something to be said, IMHO, for adding oil between oil
changes. Oil breaks down over time, and throwing in a quart every 5-10
hours replenishes the anti-wear/anti-corrosion additives as well as
increases the oil's natural ability to hold contaminants in suspension.

Well, I change my oil around 25 hours minimum, 50 hours maximum.
Hopefully
the billion-dollar-a-quart semi-synthetic Aeroshell oil holds together at
least THAT long before breaking down?

Also, I have found no hard evidence that keeping the oil topped vs. 1 or
2 quarts down provides any additional cooling or anti-wear properties.

I have no hard evidence either, but since oil flow is an important part of
cooling an air-cooled engine, I have to believe that having 50% more oil
in
the engine is going to improve cooling performance. It also follows that
having 50% more "clean" oil flushing through the engine should keep
everything internal just that much shinier?

This is no surprise, really, as the O-360 certainly doesn't *need* six
or eight quarts of oil. I know of one application (the Seminole) in
which it is certified to run on as little as 2 quarts.

Well, yes and no. While Lycoming SAYS it's okay to run them down to 2
quarts (or even less), it is nevertheless true that engine cooling will be
hurt by low oil quantities. Sometimes less is more; in this case, only
more is more.

As an adjunct to this discussion, you've got to wonder why aircraft
engines
are designed so that in the event of a leak you won't know you're out of
oil
until the last pint drains out.

The oil gauge on our engines reads pressure -- not oil capacity. As a
result, you can have a major oil leak and you will not know it until those
last few ounces vent overboard -- and THEN your oil pressure gauge drops
to
zero. We recently had a local Skyhawk pilot lose an oil line in flight,
and
he did not know he was in trouble until his oil pressure gauge finally
dropped to zero -- at which point the crankcase was already empty, and he
was frying his engine. (He made it to an airport, but destroyed the
engine.)

What baffles me is that no one has come up with an oil QUANTITY gauge like
I
have in my Mustang. This would have given the aforementioned pilot an
extra
five or ten minutes to get that plane down, BEFORE he had ruined a $16K
engine.

Anyone know?

Lastly, FWIW, my partner's other airplane (a 182) has a M20 installed.
Yes, its belly is largely free of oil residue, but it still seems to
acquire a dry, chaulky residue in any case. It looks and feels like
something you'd find just aft of an exhaust stack, and may very well
result from the exhaust...

Oh, I'm sure I'll have some exhaust stains to clean -- but at least I
(hopefully) won't have that slimy belly (with dirt and grass embedded in
it)
to clean off.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Mike Rapoport" wrote:
More oil does not improve cooling. If you think about it, it
makes sense. Where would the additoinal heat go? Same
oil cooler, same cooling fins, same baffles producing the same
airflow. The oil will actually be hotter...

....so the delta T of the oil cooler-to-air will be greater and the rate
of heat transfer will will be increased, no? Thus more heat will be
removed from the engine.

--
Dan
C172RG at BFM

"Dan Luke" wrote in message
...

"Mike Rapoport" wrote:
More oil does not improve cooling. If you think about it, it
makes sense. Where would the additoinal heat go? Same
oil cooler, same cooling fins, same baffles producing the same
airflow. The oil will actually be hotter...

...so the delta T of the oil cooler-to-air will be greater and the rate
of heat transfer will will be increased, no? Thus more heat will be
removed from the engine.

--
Dan
C172RG at BFM

I'll add a third opinion: The volume of oil doesn't drive oil temperatures
other than by providing a few more pounds of thermal mass which slightly
reduce the slope of engine temp trend lines. I.E. the engine will warm up
slightly slower and will cool off slightly slower. Once you get to steady
state operations (stabilized temps in cruise flight), you're down to the
fact that the engine transmits X BTU's to the oil, and the oil cooler
rejects Y BTU's. In steady state operations, X and Y are the same...

Kyle Boatright wrote:
"Dan Luke" wrote in message
...

"Mike Rapoport" wrote:

More oil does not improve cooling. If you think about it, it
makes sense. Where would the additoinal heat go? Same
oil cooler, same cooling fins, same baffles producing the same
airflow. The oil will actually be hotter...

...so the delta T of the oil cooler-to-air will be greater and the rate
of heat transfer will will be increased, no? Thus more heat will be
removed from the engine.

--
Dan
C172RG at BFM


I'll add a third opinion: The volume of oil doesn't drive oil temperatures
other than by providing a few more pounds of thermal mass which slightly
reduce the slope of engine temp trend lines. I.E. the engine will warm up
slightly slower and will cool off slightly slower. Once you get to steady
state operations (stabilized temps in cruise flight), you're down to the
fact that the engine transmits X BTU's to the oil, and the oil cooler
rejects Y BTU's. In steady state operations, X and Y are the same...



Except that the oil cooler isn't the only source of heat loss. Heat
from the oil is lost through the cases as well and more oil, to a point,
will reject more heat. The point is, as mentioned earlier, the point
where the oil starts to contact the crank. However, this shouldn't
happen unless you overfill the sump. The manufacturer's fill limit
should avoid windage problems with the crank.


Matt

But you are putting more heat in because of having the crank contact the oil
more of the time. The temp will be higher.

Mike
MU-2

"Dan Luke" wrote in message
...

"Mike Rapoport" wrote:
More oil does not improve cooling. If you think about it, it
makes sense. Where would the additoinal heat go? Same
oil cooler, same cooling fins, same baffles producing the same
airflow. The oil will actually be hotter...

...so the delta T of the oil cooler-to-air will be greater and the rate
of heat transfer will will be increased, no? Thus more heat will be
removed from the engine.

--
Dan
C172RG at BFM

The case has no more area and no more airflow across its surface with more
oil in the sump.

Mike
MU-2


"Matt Whiting" wrote in message
...
Kyle Boatright wrote:
"Dan Luke" wrote in message
...

"Mike Rapoport" wrote:

More oil does not improve cooling. If you think about it, it
makes sense. Where would the additoinal heat go? Same
oil cooler, same cooling fins, same baffles producing the same
airflow. The oil will actually be hotter...

...so the delta T of the oil cooler-to-air will be greater and the rate
of heat transfer will will be increased, no? Thus more heat will be
removed from the engine.

--
Dan
C172RG at BFM


I'll add a third opinion: The volume of oil doesn't drive oil
temperatures
other than by providing a few more pounds of thermal mass which slightly
reduce the slope of engine temp trend lines. I.E. the engine will warm
up
slightly slower and will cool off slightly slower. Once you get to
steady
state operations (stabilized temps in cruise flight), you're down to the
fact that the engine transmits X BTU's to the oil, and the oil cooler
rejects Y BTU's. In steady state operations, X and Y are the same...



Except that the oil cooler isn't the only source of heat loss. Heat
from the oil is lost through the cases as well and more oil, to a point,
will reject more heat. The point is, as mentioned earlier, the point
where the oil starts to contact the crank. However, this shouldn't
happen unless you overfill the sump. The manufacturer's fill limit
should avoid windage problems with the crank.


Matt