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#11
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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" |
#12
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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. |
#13
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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 $16K engine. Anyone know? Lastly, FWIW, my partner's other airplane (a 182) has a M20 installed. Yes, its belly is largely free of oil residue, but it still seems to acquire a dry, chaulky residue in any case. It looks and feels like something you'd find just aft of an exhaust stack, and may very well result from the exhaust... Oh, I'm sure I'll have some exhaust stains to clean -- but at least I (hopefully) won't have that slimy belly (with dirt and grass embedded in it) to clean off. |
#14
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"Jay Honeck" wrote in message news:OaATc.292632$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 |
#15
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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" |
#16
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"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 |
#17
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"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... |
#18
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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 |
#19
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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 |
#20
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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 |
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