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#11
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Thanks for the update. What engine is this installed on?
IO-360-C1D6 Lycoming angle valve . |
#12
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On 10-Nov-2004, tony roberts wrote: CHT's of 500/600 degrees? Definitely not. I presume he meant Fahrenheit, since he made reference to atmospheric temps in F. 350 C = 572 F. -- -Elliott Drucker |
#13
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Ron Rosenfeld wrote in message . ..
A friend corroded the cylinders on his Cardinal from continuous heating in just one winter. The water/acid boiled off the oil and condensed in the cylinders on the bottom side. I understand Tanis says that won't happen since they also have cylinder heat, but I'd be more than a little scared of it still happening. If nothing else minimize the preheat as much as convenient. Lycomings especially need preheat to keep the cam from scoring. The problem isn't bearings, it is all the expensive-to-repair surfaces like cylinders and camshaft/lifter surfaces that depend on a fog of oil for lubrication. Unfortunately if you push your luck on a cold start, the fog isn't developed for some time as the oil that blows over the relief valve has little access to the heat of the engine. After it warms up and sprays from the bearings etc, it does. |
#14
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CHT's of 500/600 degrees? Definitely not.
I presume he meant Fahrenheit, since he made reference to atmospheric temps in F. 350 C = 572 F. Cylinder head temps in that range are not recommended. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#15
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#16
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#17
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Still way too high.
Low EGT's maybe? -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE In article 9DQkd.342$fc.296@trnddc09, wrote: On 10-Nov-2004, tony roberts wrote: CHT's of 500/600 degrees? Definitely not. I presume he meant Fahrenheit, since he made reference to atmospheric temps in F. 350 C = 572 F. |
#18
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On 11-Nov-2004, Matt Whiting wrote: A friend corroded the cylinders on his Cardinal from continuous heating in just one winter. The water/acid boiled off the oil and condensed in the cylinders on the bottom side. I understand Tanis says that won't happen since they also have cylinder heat, but I'd be more than a little scared of it still happening. If nothing else minimize the preheat as much as convenient. Sounds like he had a defective heater. They shouldn't be gettings things above 212F which would be needed to boil off water or acid. Strictly speaking, as you point out, the term "boiled off" was probably in error. However, the point that moisture will be released as oil is heated is not. If water is being held in suspension, heating the oil and the air in the sump will cause some of that water to evaporate, and it may then condense on cold surfaces. It's like when you blow on cold glass. The moisture in your breath will condense and fog the glass, but your body temp is surely well below 212 F. The acid he speaks of is probably dissolved in the suspended water. -- -Elliott Drucker |
#19
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Sounds like he had a defective heater. They shouldn't be gettings things above 212F which would be needed to boil off water or acid. Matt Water vapor will slowly come off at much lower temperatures. All it needs is to condense on something cooler than the oil. I don't recall if he had crankcase heating only, or if he had cylinder heat too. I recall the jug sitting above his desk at work, very thoroughly corroded on the bottom in one winter. |
#20
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Getting oil to flow easily is only one part of the problem. As you note, this can be "solved" with a multi-viscosity oil. But another important factor is the clearance between the pistons and cylinders (or, more specifically, between the steel and aluminum parts of the engine). Because of the differential expansion/contraction of the different metals, at cold temperatures, clearance may be non-existent, so there is markedly increased wear until the engine gets above some critical temperature. The differential expansion of aluminum vs steel is 6 microinches per inch per degree F. Minimum bearing clearance is about .002 inch which would take roughly 140 degrees of chilling to fully close up. Probably even greater temps are needed for the cylinders to close up. It is certainly a significant factor, but the reduced main and rod bearing outflows (which goes as the cube of the clearance and inversely as the viscosity) is also a reason there isn't much spray inside a cold crankcase. All of these factors work against you, especially on a new or fresh majored engine having minimum clearances. Multi vis oils certainly help. Conversely having a summer weight oil greatly increases the need for thorough preheating. I use 32 degrees as a cutoff with 15W50, higher if it has been sitting for more than a week. Below that I get an oil pump cavitation whine on initial start on an O-320 E2D. |
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