M20 Air/Oil separator

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

Yes. Therefore the oil cooler will be hotter, therefore the delta T vs.
the ambient air will be higher, therefore the rate of heat transfer will
be increased, therefore more heat will be removed, therefore cooling is
improved by carrying more oil.
--
Dan
C172RG at BFM

Right, cooliong is improved (as measured by BTUs extracted) but the oil is
still hotter.

Mike
MU-2


"Dan Luke" wrote in message
...

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

Yes. Therefore the oil cooler will be hotter, therefore the delta T vs.
the ambient air will be higher, therefore the rate of heat transfer will
be increased, therefore more heat will be removed, therefore cooling is
improved by carrying more oil.
--
Dan
C172RG at BFM

You are not getting it. How much hotter do you think the case is 1" above
the oil level? About the same. The important part of this is that you are
adding more heat by raising the oil level because the crank is thrashing
about in the oil. That is why the oil is vented overboard when you fill
the case. Try different oil levels in your airplane and see for yourself.
You probably won't be able to measure the difference unless you have a
digital oil temp guage. It also take power to thrash that crank through the
oil, power that would go into turning your prop otherwise. This whole issue
is one reason why race cars use dry sump lubrication systems.

Mike
MU-2


"Matt Whiting" wrote in message
...
Mike Rapoport wrote:

The oil level is about 1" higher and the case is highly conductive.

So, 1" times the circumference of the case is a fair bit of area and
with a highly thermally conductive Al case, that will reject additional
heat to be sure.


Matt

Mike Rapoport wrote:

You are not getting it. How much hotter do you think the case is 1" above
the oil level? About the same. The important part of this is that you are
adding more heat by raising the oil level because the crank is thrashing
about in the oil. That is why the oil is vented overboard when you fill
the case. Try different oil levels in your airplane and see for yourself.
You probably won't be able to measure the difference unless you have a
digital oil temp guage. It also take power to thrash that crank through the
oil, power that would go into turning your prop otherwise. This whole issue
is one reason why race cars use dry sump lubrication systems.

No, you're not getting it. If the oil is hotter than the case, then it
will lose heat through the case. If it is losing heat through the case,
then being in contact with more case area will result in more heat transfer.

I honestly don't know if the oil contacts the crank in a typical Lyc or
Conti. It may, it may not. I'd be very surprised if it does, because
most engines with pressure lubrication systems tend to fail very quickly
when any substantial amount of oil in the sump contacts the crank. That
is why overfilling a crank is so strongly warned against by almost all
engine makers.


Matt

Don't take my word for it! Try flying your airplane full and then at
whatever the oil level stabilizes at. If the oil didn't contact the crank,
then it wouldn't be expelled out the breather (on a healthy engine). The
oil may not contact the crank in level, smooth, unaccelerated flight but it
does under acceleration, climb and descent.

Mike
MU-2


"Matt Whiting" wrote in message
...
Mike Rapoport wrote:

You are not getting it. How much hotter do you think the case is 1"
above
the oil level? About the same. The important part of this is that you
are
adding more heat by raising the oil level because the crank is thrashing
about in the oil. That is why the oil is vented overboard when you
fill
the case. Try different oil levels in your airplane and see for
yourself.
You probably won't be able to measure the difference unless you have a
digital oil temp guage. It also take power to thrash that crank through
the
oil, power that would go into turning your prop otherwise. This whole
issue
is one reason why race cars use dry sump lubrication systems.

No, you're not getting it. If the oil is hotter than the case, then it
will lose heat through the case. If it is losing heat through the case,
then being in contact with more case area will result in more heat
transfer.

I honestly don't know if the oil contacts the crank in a typical Lyc or
Conti. It may, it may not. I'd be very surprised if it does, because
most engines with pressure lubrication systems tend to fail very quickly
when any substantial amount of oil in the sump contacts the crank. That
is why overfilling a crank is so strongly warned against by almost all
engine makers.


Matt

Well, I've now flown the plane on four cross-country flights with the new
M20 installed, for a total of 5.1 hours, since Sunday.

The results: Oil level is unchanged and stable at a hair below 12 quarts,
while oil temperatures (according to the JPI engine analyzer) are
stabilizing in the 190 degree range -- unchanged from before.

Intangibles: It may be my imagination, but the prop seems to be cycling
just a tad slower than before during our pre-flight checks. I could be
crazy, though . (Mary didn't sense it, but I find that I am much more "in
tune" with mechanical things than she is...)

Could more oil in the system cause such a thing? It seems illogical, from
what I know about the variable-pitch prop system.

I just paid my son to clean the belly "one last time" today -- I hope from
now on it's just dust and dirt, not oil!

I can't really speak with any authority on the whole "putting crud
back in the crankcase" deal, but I can add that every 325-350 hp
Navajo breathes through a factory-installed air/oil sep.

The Navajo runs a higher horsepower version of my engine, right TC?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

I just checked the airwolf.com site. Let me say that I know nothing
about separators. Airwolf's website made me curious. Airwolf shows a
cutaway of the m20 to prove that it's an inferior product but not a
cutaway of their own product. They also claim that the oil from
competitor's products does not flow back to the engine until after the
engine is shutdown. Does this mean that the separator in Jay's plane is
holding four quarts of oil? Maybe the beauty of the M20 is it's
simplicity.
Dave
68 7ECA

Jay Honeck wrote:
Atlas just got his oil/air separator installed today. (For those who may
not know, Atlas is our '74 Cherokee Pathfinder, so-named because he can lift
literally anything we can fit inside!)

We picked this new accessory up at OSH '04, after much debate. (It's a
helluva lot of money for what looks like a welded tin can.) The clincher
(besides the nice clean belly) is that I'll be able to run a full 12 quarts
of oil in our Lycoming O-540, rather than the 8.5 quarts we could hold
before. (Atlas would puke out the four extra quarts, if added.)

It seems logical to assume that more oil in the engine equals cleaner oil to
all engine parts, at all times. This seems like a very good thing, indeed.

Anyone else got one of these things? Are there any "gotchas" to watch out
for, or are they as bullet-proof as they seem?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination

All,

I just checked the airwolf.com site. [...]

I did, too. It's slightly OT, but has anyone tried their remote oil-filter?
The idea looks promising (and our hangar floor would benefit from
"hassel-free" oil-filter change ;-)

Regards

Kai

"Jay Honeck" wrote in message
news:1tyUc.34503$TI1.2330@attbi_s52...
Intangibles: It may be my imagination, but the prop seems to be cycling
just a tad slower than before during our pre-flight checks. I could be
crazy, though . (Mary didn't sense it, but I find that I am much more "in
tune" with mechanical things than she is...)

Could more oil in the system cause such a thing? It seems illogical, from
what I know about the variable-pitch prop system.

Could it be that the oil is cooler (more to heat up) at the run-up
stage?

Paul

I did, too. It's slightly OT, but has anyone tried their remote
oil-filter?

Not theirs, but many years ago I raced a VW kit car and the remote oil
filter I added allowed more oil to be in the system and ceratinly allowed me
to get high power for longer before the oil temperature would climb.

Maybe having it in a remote location with some air flow allowed a better
cooling, and maybe the increased oil capacity helped by allowing for a
slower overall climb in temperature. It certainly helped to maintain a more
stable temperature with the short periods of full power that I subjected it
to in motorkana events.

An aircraft is normally only subjected to full power for take off and go
round, and many manufacturers quote full power rating for one minute or
similar times.

Hope this helps,
Peter