Which rule is now wrong?

Let'sgoflying!

Let'sgoflying!

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Dave Taylor
LOP and breaking in cylinders.

Seems I am learning about breaking in cyl's LOP.

There are, or used to be two (unrelated, but) inviolable tenets. With the new LOP break-in procedure I am reading about, one of these are being discarded but I can't tell which.


A )
One is, (or used to be), "Never run LOP down low, or at least not above 65(v75)% hp."

B )
The other is (or was), "Always break in the cylinders at higher power settings, ie >75%hp". Also known as the "Don't baby your engine" mantra.
 
I have used this method for several years and have had no problems.

http://www.eci.aero/pages/tech.aspx

The cylinder honing has changed, and it requires very little run time to seat rings. in most cases the test stand time is enough to seat the rings. and after that you can run normally as the POH requires.

LOP has no effect on cylinder break in, you can get as much power that way as you can on the rich side.

And power is what applies pressure to the rings not mixture, and a rich mixture only washes the cylinder walls with excess fuel.
 
Not sure about LOP down low. Even under full load conditions, valve temperatures remain low due to the low mass flow rate of gases and long seating time of the valve. Combustion tempuratures will remain high and may lead to pre-ignition or knock. Without knowing exactly how the cylinder runs (pressure transducers), the 75% number for power seems pretty good.

Breaking cylinders in hard is a balance between preventing the rings from glazing and breaking in the journal bearings lightly so as to wear in the imperfections without causing galling, etc. New cylinders only, a hard break-in would be prudent. Full engine overhaul, lighter, balanced break-in.

Although I would ALWAYS follow the manufactured recommended break-in since every engine model requires something just a bit different.
 
No answer yet.

The question is,

Do we run >75% power to break in the cylinders breaking rule A?
or
Do we run <75% power to break in the cylinders, breaking rule B?

Sorry for the confusing initial post.
 
You guys best read the procedures given above because that is not what they advise.

quote

Use take-off power only as long as necessary to get to BEST CLIMB SPEED.
Reduce manifold pressure to minimum required for clean in-flight attitude. Leave
propeller in flat pitch for at least 5 minutes after take-off. For aircraft not equipped
with a variable pitch propeller or manifold pressure gauge, reduce power to 75%.
Use minimum rate of climb with maximum air speed consistent with terrain.
 
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TripleZ said:
Not sure about LOP down low. Even under full load conditions, valve temperatures remain low due to the low mass flow rate of gases and long seating time of the valve. Combustion tempuratures will remain high and may lead to pre-ignition or knock. Without knowing exactly how the cylinder runs (pressure transducers), the 75% number for power seems pretty good.

Breaking cylinders in hard is a balance between preventing the rings from glazing and breaking in the journal bearings lightly so as to wear in the imperfections without causing galling, etc. New cylinders only, a hard break-in would be prudent. Full engine overhaul, lighter, balanced break-in.

Although I would ALWAYS follow the manufactured recommended break-in since every engine model requires something just a bit different.
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I don't know where you got your info. but that isn't advised by either of the major engine manufacturers or any after market cylinder manufacturers.

Plus did you know the tightest bearing journal fit is .002" that is .002" of oil film between the crank and the bearing shell. If any engine is set up properly it will never turn a bearing (Gaul) You must have a tremendous amount of heat and pressure to do any damage to the main or rods of these engines.

preoil, preoil, preoil, then do it again.
 
Tom-D said:
I don't know where you got your info. but that isn't advised by either of the major engine manufacturers or any after market cylinder manufacturers.

Plus did you know the tightest bearing journal fit is .002" that is .002" of oil film between the crank and the bearing shell. If any engine is set up properly it will never turn a bearing (Gaul) You must have a tremendous amount of heat and pressure to do any damage to the main or rods of these engines.

preoil, preoil, preoil, then do it again.
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I'm a development engineer for an engine company. Every engine is different hence the generalization and "ALWAYS follow the manufacturer recommended break-in". We run tight main and rod clearances, so a light initial start to the break-in is important (and it's good for the valve train), then ramped up in load to break-in the rings.

I will not profess that I know the correct break-in for an air-cooled engine, just that there's many opinions on the correct way. And since machining technology has improved, some of the reasons for what was done during a break-in has changed.

preoil, preoil, preoil, then do it again.
Click to expand...
And yes, this is very important.
 
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TripleZ said:
I'm a development engineer for an engine company. Every engine is different hence the generalization and "ALWAYS follow the manufacturer recommended break-in". We run tight main and rod clearances, so a light initial start to the break-in is important (and it's good for the valve train), then ramped up in load to break-in the rings.

I will not profess that I know the correct break-in for an air-cooled engine, just that there's many opinions on the correct way. And since machining technology has improved, some of the reasons for what was done during a break-in has changed.
Click to expand...

I overhaul and repair aircraft engines..... and restore antique and classic aircraft as a hobby.

I have rebuilt (2) 0-320, (1) 0-360, Lycomings, (1) Franklin 165, and (4) 0-200, this year. and now have a Warner 165 on the build stand.

So, believe me, we follow standard overhaul procedures and we never see gaulded bearings on the test stand and never in service engine failures due to too tight bearings, it is almost always metal contamination impregnated into the bearing shell that destroys a crank.
 
I always seat rings lean, they seat faster and you don't have all that fuel washing them out so your chances of glazing one are lower. Normally I seat a cylinder in the first hour or so.
 
Henning said:
I always seat rings lean, they seat faster and you don't have all that fuel washing them out so your chances of glazing one are lower. Normally I seat a cylinder in the first hour or so.
Click to expand...

I don't even worry about it, by the time I have all the leak check runs complete, you can fly it as you normally do.

WE watch the CHTs and oil consumption for a few hours until the pilot builds confidence in it.

Change oil at 5 hours and again at 25. see what is coming out.l
 
Tom-D said:
I overhaul and repair aircraft engines..... and restore antique and classic aircraft as a hobby.

I have rebuilt (2) 0-320, (1) 0-360, Lycomings, (1) Franklin 165, and (4) 0-200, this year. and now have a Warner 165 on the build stand.

So, believe me, we follow standard overhaul procedures and we never see gaulded bearings on the test stand and never in service engine failures due to too tight bearings, it is almost always metal contamination impregnated into the bearing shell that destroys a crank.
Click to expand...

Agreed, either metal impregnated into the shell, or residual grind / machining chips left in an oil passage.

By gauling, I mean surface gauling of the shell not spinning. Typically caused by inclusions in the crank pin from "dirty" material or high spots in the shell or pin surface from "non-flat" grinding. Both quality defects. A light break-in allows the bearing shell to self clearance, instead of causing localized contact and melting "gauling". It looks like a small melted trail of material part of the way around the shell.

I don't doubt you've never seen it. For one, your working with higher quality materials "clean steel / bearing grade" cranks and your quality controls are probably much higher than automotive non-critical engines.

It's something I've seen in development engines and some field returns. (non-aviation of course) It can happen, but rare, and can be prevented with most break-ins. Our cranks are ground in Korea and assembled by someone who has maybe 60 days on that line position. ;). Yay! For unskilled labor.
 
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Dave,

A) is wrong. It's at high power settings that you DO want to run LOP. High power settings are where ROP can do the most damage and where it wastes the most fuel.

I'm sure this will generate another unnecessary discussion on PoA. Unnecessary because this has been asked and answered for 40+ years,
 
TripleZ said:
Agreed, either metal impregnated into the shell, or residual grind / machining chips left in an oil passage.

By gauling, I mean surface gauling of the shell not spinning. Typically caused by inclusions in the crank pin from "dirty" material or high spots in the shell or pin surface from "non-flat" grinding. Both quality defects. A light break-in allows the bearing shell to self clearance, instead of causing localized contact and melting "gauling". It looks like a small melted trail of material part of the way around the shell.

I don't doubt you've never seen it. For one, your working with higher quality materials "clean steel / bearing grade" cranks and your quality controls are probably much higher than automotive non-critical engines.

It's something I've seen in development engines and some field returns. (non-aviation of course) It can happen, but rare, and can be prevented with most break-ins. Our cranks are ground in Korea and assembled by someone who has maybe 60 days on that line position. ;). Yay! For unskilled labor.
Click to expand...

When companies build dirty engines and leave stuff in the engines you will see a lot of bad things.
 
sba55 said:
Dave,

A) is wrong. It's at high power settings that you DO want to run LOP. High power settings are where ROP can do the most damage and where it wastes the most fuel.

I'm sure this will generate another unnecessary discussion on PoA. Unnecessary because this has been asked and answered for 40+ years,
Click to expand...

Old wives tales die hard.
 
Tom-D said:
Old wives tales die hard.
Click to expand...

That one is hard to die because it is the factory word from Continental and in the Columbia 400 POH. LOP operation is not recommended at any time above 65% power, period.

I personally think it's a recommendation to reduce the risk of some poor workmanship thats showing up in Contis but it doesn't matter. Are you going to run your engine the way you wish it was made or in accordance with the way they actually made it and factory reccomends you run it?
 
Let'sgoflying! said:
LOP and breaking in cylinders.

Seems I am learning about breaking in cyl's LOP.

There are, or used to be two (unrelated, but) inviolable tenets. With the new LOP break-in procedure I am reading about, one of these are being discarded but I can't tell which.


A )
One is, (or used to be), "Never run LOP down low, or at least not above 65(v75)% hp."

B )
The other is (or was), "Always break in the cylinders at higher power settings, ie >75%hp". Also known as the "Don't baby your engine" mantra.
Click to expand...

What about running ROP at high power discards either of these choices?
 
PittsDriver said:
That one is hard to die because it is the factory word from Continental and in the Columbia 400 POH. LOP operation is not recommended at any time above 65% power, period.

I personally think it's a recommendation to reduce the risk of some poor workmanship thats showing up in Contis but it doesn't matter. Are you going to run your engine the way you wish it was made or in accordance with the way they actually made it and factory reccomends you run it?
Click to expand...

You need to read "tips on engine care" from TCM.It's form X30548 Rev 2
 
PittsDriver said:
That one is hard to die because it is the factory word from Continental and in the Columbia 400 POH. LOP operation is not recommended at any time above 65% power, period.

I personally think it's a recommendation to reduce the risk of some poor workmanship thats showing up in Contis but it doesn't matter. Are you going to run your engine the way you wish it was made or in accordance with the way they actually made it and factory reccomends you run it?
Click to expand...

I think it's to reduce the chance of damage because the majority of people only learn how to do something "half right" and fail to pay attention. There is also the matter of selling more cylinder kits by maintaining the ROP legends.
 
Tom-D said:
You need to read "tips on engine care" from TCM.It's form X30548 Rev 2
Click to expand...

I don't have it and it looks like I've have to order it to read it. I might order it if you think it's got some useful insight on Continental's assertions. I have had the Columbia factory training which taught LOP operation with the assertion that there was a "wink wink" endorsement from Continental. The POH says no LOP operation over 65%. When the jugs where all swapped last year at about 700 hours, Continental said that they never endorsed running the engine the way Columbia taught it (up to 85% power LOP) and that running that way is what pitted the valves and valve seats. We always ran the engine at 31.5"/2450 at about 100 LOP (works out to about 75 - 80% power) and it ran trouble free until it was recommended to replace the jugs at the last annual.

By my calculations, the fuel we saved paid for the jugs about 3 times over and running it that way lost only about 8 - 10 kts vs. 100 ROP. I don't understand the problem running it LOP unless it there's some lubricating effect on the valves and valve seats of the rich operation. The engine's running cool and at a reasonable power setting either ROP or LOP so I concluded, based upon some other anecdotal information about Conti's manufacturing of the engines that the recommendations from Conti were appropriate to extend the life of the valves/valve seats based upon how the engine is now being made.

The Lycoming in my Pitts won't run smoothly LOP so I just always run it well ROP. I've got over 400 hours of pretty abusive time on it and the compression hasn't changed on it in 375 hours. If it would run well LOP I'd probably run it there when traveling in it to get better range off my tiny fuel tank. But it's never been enough of an annoyance to go get the injectors balanced to run it that way. It's spent most of it's life firewalled going up and down right over an airport.
 
Henning said:
I think it's to reduce the chance of damage because the majority of people only learn how to do something "half right" and fail to pay attention. There is also the matter of selling more cylinder kits by maintaining the ROP legends.
Click to expand...

That's always been Lycoming's position - that pilots don't tend to do LOP operation well enough, with good enough instrumentation, or with diligent attention to procedures to worry about making an engine a) will run smoothly LOP; and b) that they can recommend running LOP.
 
Let'sgoflying! said:
Thats what I want to do but I got my a$$ handed to me on a plate for that suggestion on another board.
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Do the folks on that other board pay your maintenance bills? :) Seriously, if you listen to all the various opinions, mythologies, wives tales, and outright lies you'll find from a survey of web forums, you'll never reconcile or distill out any technique that won't trash your engine. I've felt my own engine experiences to be satisfying but that may just be more a fluke of drawing some good engines than my own personal procedures. I've owned 2 big conti turbo'd engines, 3 big Lycoming TC's, and a couple of normally aspirated big Lycomings and put a couple of thousand hours on the lot of them. Ultimately, you have to give some serious cred to the manufacturer and what they tell you to do. I'm not a huge fan of conspiracy theories like the "we want to really sell you a bunch of jug kits" kind but nothing surprises me anymore.
 
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