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#1
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M20 Air/Oil separator
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 |
#2
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Jay,
Doesn't the air/oil separator simply catch the oil the engine pukes, so the oil doesn't end up on the belly? If that's the case, your separator better have a capacity of almost 4 quarts, 'cause I suspect the engine is still gonna send the first 3.5 quarts out the breather. KB "Jay Honeck" wrote in message news:CyfTc.304529$XM6.124022@attbi_s53... 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 |
#3
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Doesn't the air/oil separator simply catch the oil the engine pukes, so
the oil doesn't end up on the belly? If that's the case, your separator better have a capacity of almost 4 quarts, 'cause I suspect the engine is still gonna send the first 3.5 quarts out the breather. Yes and no. It constantly feeds the puked out oil back into the crankcase, so you can run with a full crankcase instead of one that is 1/3 empty. I'm no mechanic, but more fresh oil sounds good for my engine. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#4
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From what I've read here on Rec. Av. * the downside to these oil
separators is that they may also return the moisture, acids, and other products of combustion that volatilize and go out the breather tube, back to your crankcase. If you've had oil analysis done in the past I would certainly be interested if this seems to be the case. Joe Schneider 8437R "Jay Honeck" wrote in message news:XUnTc.150507$eM2.144868@attbi_s51... Doesn't the air/oil separator simply catch the oil the engine pukes, so the oil doesn't end up on the belly? If that's the case, your separator better have a capacity of almost 4 quarts, 'cause I suspect the engine is still gonna send the first 3.5 quarts out the breather. Yes and no. It constantly feeds the puked out oil back into the crankcase, so you can run with a full crankcase instead of one that is 1/3 empty. I'm no mechanic, but more fresh oil sounds good for my engine. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#5
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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!) snip Anyone else got one of these things? Are there any "gotchas" to watch out for, or are they as bullet-proof as they seem? Hi Jay, A few comments. 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. 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. 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. If we keep our 172's O-360 between 6 and 7 quarts (max 8), our belly remains reasonably clean and it runs at what I'd call "nominal" temperature. 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. I'm sure other Lycoming engines such as your O-540 are the same in this regard. As long as you maintain the minimum required oil level, a couple quarts down isn't going to make any difference except on a LONG ferry flight where you can't add oil in flight. Most POH's seem to reflect this (e.g. "Top off for extended flight"). 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...I don't know for sure. But, I do know that the belly is still dirty enough after 50 hours that I have an overwhelming desire to break out the creeper and WD40, so I'm convinced an oil separator would save me no labor. :-) Safe flying, -Doug -- -------------------- Doug Vetter, CFIMEIA http://www.dvcfi.com -------------------- |
#6
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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" |
#7
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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. |
#8
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#9
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Any aircraft engine crankcase I've been inside of has relatively small
slots below the crank where the case halves meet effectively isolating the sump from the crank in regard to "windage". Ah! The man who truly *knows* weighs in! :-) So how 'bout it, TC -- is the M20 a good thing, a bad thing, or 'bout the same thing with regards to my O-540? -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#10
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John_F wrote: 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. My guess would be that your engine makes only 50% or less, much less at 14,000 feet, percent power, and it won't use much oil at such low power settings. |
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