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  #11  
Old 01-23-2019, 08:08 PM
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rocketbob rocketbob is offline
 
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Quote:
Originally Posted by 777Dave View Post
My A&P figures about 50 hours before it will be fully broken in.
Its nonsense, old wives tale. It takes just a few minutes to break in a Lycoming. I've proven it, and have a little demonstration I do on engines I overhaul, before and after the first run.

Imagine taking a fine file to a piece of steel for 10,000 strokes (2500 rpm x 4 min) and think that one's effort doing so would have a negligible effect, and instead it would take hours of this to effort to have a measurable effect.

NEVER EVER get cylinders hot at breakin. Guaranteed to glaze.
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  #12  
Old 01-23-2019, 11:01 PM
lr172 lr172 is offline
 
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Originally Posted by rocketbob View Post
Its nonsense, old wives tale. It takes just a few minutes to break in a Lycoming. I've proven it, and have a little demonstration I do on engines I overhaul, before and after the first run.

Imagine taking a fine file to a piece of steel for 10,000 strokes (2500 rpm x 4 min) and think that one's effort doing so would have a negligible effect, and instead it would take hours of this to effort to have a measurable effect.

NEVER EVER get cylinders hot at breakin. Guaranteed to glaze.
While I would agree that Plateau honed (400 grit stones) cylinders will often fully seat the rings in a few minutes, traditionally honed cylinders (220 grit) take a few hours to fully break in (certainly not 50, more like 3-5). After the first few minutes, the peaks flatten off a bit and it is now like a very dull file and a dull file worked over an oil coated interface just doesn't do a lot. Takes a LOT of repetition. I don't know about lycoming, but do know that superior still uses 220 grit final honing. ECI told me they are using 400 grit honing, but still see about 3-4 hours for full ring seating on their test stands.

Further, glazing can, generally speaking, only occur on cylinders where the rings haven't fully seated (the valleys are still too deep, leaving too thick of an oil film). 450* with unseated rings causes glazing. 450* with seated rings creates no glazing. The fact that you can't get a cylinder to 450* in a few minutes pretty much confirms that rings don't seat in a few minutes, as glaizing is still prevelant.

This is further backed up by people seeing their CHTs drop after a few hours. All of the friction involved in wearing down the ridges produces a LOT of heat. The same logic drive the conventional wisdom that the rings have seated when the CHT's drop / stabilize. Oil consumption also drops due to valleys getting more shallow and leaving less oil exposed to the hot combustion gasses.

Larry
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Last edited by lr172 : 01-23-2019 at 11:23 PM.
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  #13  
Old 01-24-2019, 06:47 AM
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777Dave 777Dave is offline
 
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CHTs are good, it?s just fuel flow that seems high in spite of leaning. I?ll see if that improves over time.
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  #14  
Old 01-24-2019, 07:00 AM
Kyle Boatright Kyle Boatright is offline
 
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Originally Posted by 777Dave View Post
CHTs are good, it?s just fuel flow that seems high in spite of leaning. I?ll see if that improves over time.
It won't. Unless your mixture balance is "off" between cylinders, the only ways to reduce fuel flow will be to lean further or run at lower power settings.

Have you verified the accuracy of your fuel flow readings?
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  #15  
Old 01-24-2019, 07:23 AM
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rocketbob rocketbob is offline
 
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Originally Posted by lr172 View Post
While I would agree that Plateau honed (400 grit stones) cylinders will often fully seat the rings in a few minutes, traditionally honed cylinders (220 grit) take a few hours to fully break in (certainly not 50, more like 3-5). After the first few minutes, the peaks flatten off a bit and it is now like a very dull file and a dull file worked over an oil coated interface just doesn't do a lot. Takes a LOT of repetition. I don't know about lycoming, but do know that superior still uses 220 grit final honing. ECI told me they are using 400 grit honing, but still see about 3-4 hours for full ring seating on their test stands.
I have a nice collection of Sunnen hone stones of varying grits and materials, a plateau brush, brush research dingleberry brushes. I've experimented with them all and found little difference in oil consumption. My preference, however, is a plateau finish. I haven't noticed any difference in break in time but they sure sound different on a brand new engine as you pull the prop thru. 280 grit with a plateau finish sounds scary. After the first run, the scary sound is gone. In less than 5 minutes of running.

Some auto makers engines are run in on the assembly line without sparkplugs using a large electric motor to turn the motor over. The idea is to not have the heat and oil contamination interfering with the run in process. They only do this for a few minutes.

Quote:
Originally Posted by lr172 View Post
Further, glazing can, generally speaking, only occur on cylinders where the rings haven't fully seated (the valleys are still too deep, leaving too thick of an oil film). 450* with unseated rings causes glazing. 450* with seated rings creates no glazing. The fact that you can't get a cylinder to 450* in a few minutes pretty much confirms that rings don't seat in a few minutes, as glaizing is still prevelant.
Glazing has nothing to do with ring seating. It has everything to do with the cylinder getting too hot. I've seen chrome cylinders glazed on engines with fully seated rings, where upon inspection the rings were completely polished uniformly all the way around. I've seen engines which were mismanaged glaze cylinders.

Quote:
Originally Posted by lr172 View Post
This is further backed up by people seeing their CHTs drop after a few hours. All of the friction involved in wearing down the ridges produces a LOT of heat. The same logic drive the conventional wisdom that the rings have seated when the CHT's drop / stabilize. Oil consumption also drops due to valleys getting more shallow and leaving less oil exposed to the hot combustion gasses.

Larry
This also is rehashing old thinking. Last summer I borrowed a friend's 200hp RV7 with just a few hours on a boutique engine overhaul to go on a trip. He warned me about it getting hot on climb due to it not being broken in. On climb temps were headed up over 420 and I started slowly and carefully leaning. CHT' in climb immediately stopped rising. Temps came right back down to 380 with no loss of MP. FF dropped just a few tenths.
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N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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  #16  
Old 01-24-2019, 08:46 AM
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777Dave 777Dave is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post
It won't. Unless your mixture balance is "off" between cylinders, the only ways to reduce fuel flow will be to lean further or run at lower power settings.

Have you verified the accuracy of your fuel flow readings?
Carbureted engine. FlowScan fuel flow meter that was used with the old engine.
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  #17  
Old 01-27-2019, 08:59 PM
Rallylancer122 Rallylancer122 is offline
 
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I have an O-360 in another plane and 24 square is 75% power. With the carb I can't go lean of peak as the mixture balance is off between the cylinders (as verified by a graphic engine monitor), but leaned until it's rough and then richened a bit gives 9gph. Per Lycoming you cannot hurt the engine leaning at 75% or below. 22" and 2300 gives 65%, and 8gph.

DEM
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  #18  
Old 05-28-2019, 02:32 PM
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Nived17 Nived17 is offline
 
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Location: Williamsport, PA
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Default hot CHTs on new o320

[quote=This also is rehashing old thinking. Last summer I borrowed a friend's 200hp RV7 with just a few hours on a boutique engine overhaul to go on a trip. He warned me about it getting hot on climb due to it not being broken in. On climb temps were headed up over 420 and I started slowly and carefully leaning. CHT' in climb immediately stopped rising. Temps came right back down to 380 with no loss of MP. FF dropped just a few tenths.[/QUOTE]

Can you talk a little more about this for me. I have 12 hours on a complete overhaul on an o320. I am seeing 420 degrees on climb outs down low. I am still running 100 mineral oil. They settle to around 380 in cruise at altitude. One other piece to note is that it is 100 degrees air temp here in SC. Any suggestions? Anything that I should be looking for or doing differently. This O320 was upgraded from 7:1 to 8.5:1 pistons and cylinders as wells as the matching carb. My first plan of attack will be with silicone in the baffling.
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  #19  
Old 05-28-2019, 04:37 PM
Norman CYYJ Norman CYYJ is offline
 
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Move north for the summer for cooler OAT.
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  #20  
Old 05-28-2019, 05:18 PM
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Nived17 Nived17 is offline
 
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Default Truth!

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Originally Posted by Norman CYYJ View Post
Move north for the summer for cooler OAT.
You sound like my mother asking me to move back to PA! 😂
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