Question about engine overhaul break-in procedures

Greg Bockelman

Greg Bockelman

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Background. Continental O-200 freshly overhauled. Field overhaul.

One school of thought is to run it hard for the first 25 hours. Pretty much full throttle, or at least a high percentage of power, limiting operation at lower RPM's as much as possible.

The other school of thought is to baby it. Not run it hard at all. Varying power settings every 15 minutes or so.

So, which one is correct? One mechanic says one way, another says another.

FWIW, I had always been told to run it hard for the first 25 hours or so.
 
Well, I just found a document put out by Continental Engines that suggests a power setting between 65% and 75% power at best power mixture setting. Hmm.
 
ive seen two brand new engines end up with glazed cylinders after inspection from running too hot. Manage the heat at high enough power to seat the rings and you should be good. As normal, follow Conti recommendations.

I liked this info when I was looking at a penn yan or mattituck replacement engine years ago. http://www.mattituck.com/articles/engbrkin.htm
 
Most engines are "run hard".

Need to have enough pressure on the rings to grind away microscopic amounts of "rough" metal in the cylinder bore and to push the rings down and out at each firing of the cylinder to the correct location, so they'll seat and you won't have slop and lots of blow-by.

Two cylinders replaced on a CAP bird earlier this year. Manufacturer wanted continuous high power as much as possible for a specified number of hours. No pattern work, as few takeoffs and landings as necessary. Aircraft was restricted to only XC flights until that time wore off and mechanic confirmed the oil consumption had stabilized.

Regularly see aircraft up here at high DA where it's hard to get 75% power have to pull a jug and "score" it, then put it back on and try again to get oil consumption down.

So, the correct answer these days is "whatever the manufacturer recommends" since you'd like to keep your warranty. I'm sure they have a Service Bulletin for cylinder break-in. Typically "run hard with straight mineral oil" for a certain number of hours combined with oil consumption stabilizing.
 
Greg Bockelman said:
Background. Continental O-200 freshly overhauled. Field overhaul.

One school of thought is to run it hard for the first 25 hours. Pretty much full throttle, or at least a high percentage of power, limiting operation at lower RPM's as much as possible.

The other school of thought is to baby it. Not run it hard at all. Varying power settings every 15 minutes or so.

So, which one is correct? One mechanic says one way, another says another.

FWIW, I had always been told to run it hard for the first 25 hours or so.
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When I do a 0-200 I tell the owner / pilot to run it normally, full throttle for take off, and cruise it at 2450 leaned to stutter and richened to smooth.

Contrary to old wives tales the pressure in the cylinder at idle will seat the rings. running at high power settings simply overheats the engine and takes the temper out of the rings and allows them to collapse into their grooves and oil usage never goes down, so every one says the cylinders is glazed. Which isn't even close to what really happens.

Go fly it normally it will be OK. you will notice when oil usage drops. then change the oil and filter. ( yes filter ) if you don't have one, get one.
 

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Tom-D said:
Go fly it normally it will be OK. you will notice when oil usage drops. then change the oil and filter. ( yes filter ) if you don't have one, get one.
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The general rule is that the break-in is complete when engine temperatures drop and oil consumption stabilizes. And it shouldn't take 25 hours for that to happen -- more like 10-15. Once that happens, it's time to remove the straight mineral oil and start on ashless dispersant.
 
Wait. Apologies in advance for the segue, but this got me wondering.

The engine is running hardest when it's starved for air, no? that is, idle throttle, when the pistons are working their rings off to suck in what little air they can. In full open throttle, the engine has as much air as it wants, and is running most efficiently, which to me means running quite a bit easier.

Am I getting something wrong here?
 
onwards said:
Wait. Apologies in advance for the segue, but this got me wondering.

The engine is running hardest when it's starved for air, no? that is, idle throttle, when the pistons are working their rings off to suck in what little air they can. In full open throttle, the engine has as much air as it wants, and is running most efficiently, which to me means running quite a bit easier.

Am I getting something wrong here?
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The pressures from combustion are much higher when there's more oxygen and fuel to burn (at full throttle and optimum mixture). That's much more than the pressure to suck in air.

John
 
I am nothing close to an expert but I too have heard the run it hard instruction. I suspect Ted will be along and let us know his thoughts and experiences.
 
Run it like you would if it was a mid time motor with a few exceptions...

1- Pull the cowl off every few hours and give the motor a once over to see if all is well...

2- Limit idle and taxi time to the bare minimum, altho let the motor warm up and you see the oil temp gauge move up.

3- Keep the nose down and airspeed up while running it fairly hard. This will allow the components to seat in and the cyl temps to say in the normal range... Do NOT climb at VX all the way to 10,000 msl while wide open.....:no:.

4- Once the temps stabilize and the oil comsumption settles down to normal levels get the mineral out and aviation oil in with a filter change included.

If the motor was properly built and you get the first 10 -15 hours safely under your belt the engine will outlast most of us on here...:yesnod::wink2:
IMHO................

Ben.
 
onwards said:
Wait. Apologies in advance for the segue, but this got me wondering.

The engine is running hardest when it's starved for air, no? that is, idle throttle, when the pistons are working their rings off to suck in what little air they can. In full open throttle, the engine has as much air as it wants, and is running most efficiently, which to me means running quite a bit easier.

Am I getting something wrong here?
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FWIW - This is a random pressure (vertical) volume (horizontal) diagram of the in-cylinder pressures from a 6 cylinder automobile engine running at a moderately light load.

attachment.php


A is the start of the compression stroke (intake valve closes), B is about when the spark plug fires near the top of the stroke, C is when combustion is winding down during the expansion stroke, D is exhaust valve opening, E bottom of the stroke starting the exhaust stroke, F is the top of the stroke exhaust stroke, start of intake. Which brings us back to A.

The exhaust pressure is close to atmospheric so you can see that there is about a .5 bar pressure drop against the rings (about 15 in Hg) during the intake, but up to 30 bar during combustion. Running at 75% power would raise the pressures on the expansion stroke quite a bit - probably about three times what you see here. I would also point out that this is a log-log scale so the difference in pressure as you go up the axis is larger than it looks.

Note: This diagram has a "funny" shape for the intake stroke compared to an aircraft engine because it was running with a late intake valve opening / closing to improve fuel economy at this power setting.
 

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Greg Bockelman said:
Well, I just found a document put out by Continental Engines that suggests a power setting between 65% and 75% power at best power mixture setting. Hmm.
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I don't think you're going to find an absolute answer. Some will say to run it hard, others will say to run it normally, others will say to baby it. If it were mine I'd run it hard. But quite frankly I don't think it really matters all that much because there are so many schools of thought and so many people that do opposite things during break in but the end result seems about the same. I am sure the vast majority of the "breaking in" is done during the first few rotations of the motor.

Not that relevant to an airplane, but when I bought my new motorcycle last year I spent quite a bit of time researching trying to come to a conclusion. I finally decided to do the break in procedure as per the performance motorcycle engine building shops which involved avoiding a constant power setting and loading the engine up to higher power settings. Eventually working your way up to redline. Kind of tricky to do on the street though because the damn thing is so fast.

Kawasaki said to limit power to 3000 RPM for the first 500 miles but the general theory is that they:
a) didn't want you to stress their new engine and make it more likely to have an issue if they built it weak
b) didn't want a bunch of idiot racing down residential streets doing 150 mph trying to "break in" their engine.
c) it really didn't matter that much how you broke the engine in, and they're more worried about "breaking new riders in" therefore telling them to ride really slow at first.

FWIW the bike doesn't burn a drop of oil. But you really can't compare it to an airplane engine - because it's quite different. Not sure why I even bothered to type the above :)
 
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jesse said:
I don't think you're going to find an absolute answer. Some will say to run it hard, others will say to run it normally, others will say to baby it.
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I don't think you'll find anyone in the engine manufacturing/overhaul business telling you that last part.
 
jesse said:
c) it really didn't matter that much how you broke the engine in, and they're more worried about "breaking new riders in" therefore telling them to ride really slow at first.
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That would be my guess
 
Am I getting something wrong here?
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I am thinking icp is correlated positively to available fuel and air.
More f+a means more combustion is happening, higher icp and outward force on the rings.
 
Ron Levy said:
The general rule is that the break-in is complete when engine temperatures drop and oil consumption stabilizes. And it shouldn't take 25 hours for that to happen -- more like 10-15. Once that happens, it's time to remove the straight mineral oil and start on ashless dispersant.
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I never advise running any thing but 20W50 phillips day 1 to TBO in the 0-200. or any engine for breakin.

Another old wives tale that refuses to go away.

the new cylinders are finished honed with a fine stone, and will have seated the rings and be ready to fly before you can get the leak check done.
Plus the fact that using full throttle for take off, and 2450 for cruise is well within limits of all the cylinder manufacturers recommendations.

and that is normal operation for the 0-200/300
 
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Running it hard does not mean running it hot. Running it hard will seat the rings better. Lycoming SI 1427C dictates their recommended procedure. If you run it too hot, yes, the rings will glaze. Limits are not goals.

If you are doing it properly, you will still be keeping the CHTs within reasonable numbers. Yes, they will be hotter than normal. As the rings seat and the cylinder breaks in, you will actually be able to watch the CHTs drop on your engine monitor.
 
For the general fund of information, I flew the plane for an hour and a half today. Two landings. 2500 RPM plus or minus. The only temperature gauge on the plane is an oil temp with a green arc from 100 to 225 degrees. The oil temperature never got above about 115 to 125 degrees, IF it is accurate. Not much instrumentation on a 1963 150. Just oil temp. FYI, OAT was 0 C/32 F.
 
Greg Bockelman said:
For the general fund of information, I flew the plane for an hour and a half today. Two landings. 2500 RPM plus or minus. The only temperature gauge on the plane is an oil temp with a green arc from 100 to 225 degrees. The oil temperature never got above about 115 to 125 degrees, IF it is accurate. Not much instrumentation on a 1963 150. Just oil temp. FYI, OAT was 0 C/32 F.
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If it ran fine, it's good to go. treat it like it has a 1000 hours on it.
 
Tom-D said:
I never advise running any thing but 20W50 phillips day 1 to TBO in the 0-200. or any engine for breakin.

Another old wives tale that refuses to go away.

the new cylinders are finished honed with a fine stone, and will have seated the rings and be ready to fly before you can get the leak check done.
Plus the fact that using full throttle for take off, and 2450 for cruise is well within limits of all the cylinder manufacturers recommendations.

and that is normal operation for the 0-200/300
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So there's no need for break-in?

Because the rings are seated and the cylinders are already honed, I guess the engine is good to go.
 
Cap'n Jack said:
So there's no need for break-in?

Because the rings are seated and the cylinders are already honed, I guess the engine is good to go.
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With todays cylinders for the 0-200/300 that is pretty much true, any oil that is not an "EP" oil is good for break-in. there is no need to run mineral oil for break in any more.
 
onwards said:
Wait. Apologies in advance for the segue, but this got me wondering.

The engine is running hardest when it's starved for air, no? that is, idle throttle, when the pistons are working their rings off to suck in what little air they can. In full open throttle, the engine has as much air as it wants, and is running most efficiently, which to me means running quite a bit easier.

Am I getting something wrong here?
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Yes, BTUs of the fuel flowed, pressure, kinetic energy and inertia are all factors that work against your theory.
 
Cap'n Jack said:
So there's no need for break-in?

Because the rings are seated and the cylinders are already honed, I guess the engine is good to go.
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Pretty much, the days of hand fitted babbit bearings are long gone. The only way you'll really screw up seating a set of rings is to run too rich or too hot. Outside of that, they're gonna be fine.
 
The big question is what changed, why don't we need mineral oil for break in any more?
 
So, is it OK to run : Oil 65, 80, 100 Straight Grade Engine Oils the entire life of the engine ?
 
Amazing and good timing on this thread! I just took the plane home this afternoon following my annual and a top overhaul. 4 new steel lycoming cylinders (O-360-A3A-180) and I put in a JPI-EDM700. My question is to you guys who are familiar with the JPI, since this is my first exerience with an analyzer. My A&P flew the plane for an hour yesterday to do the sign off and told me that the cylinders were basically broken in during that first hour. I flew the plane for another hour today 3.5Kft at around 2450-2500RPM and full rich, EGT's were around 1365-1400 and CHT's 380-395, oil temp never above 189deg. But I did see the #2 cylinder consistently cooler than the others. When I powered down for the approach, things evened out across the board. I know I have to get used to working with the JPI, but am wondering what anyone else has seen during break-in and having an analyzer. I am concerned about running the engine too hot and glazing the cylinders. Is full rich mixture necessary? Thanks.
 
DutchessFlier said:
Amazing and good timing on this thread! I just took the plane home this afternoon following my annual and a top overhaul. 4 new steel lycoming cylinders (O-360-A3A-180) and I put in a JPI-EDM700. My question is to you guys who are familiar with the JPI, since this is my first exerience with an analyzer. My A&P flew the plane for an hour yesterday to do the sign off and told me that the cylinders were basically broken in during that first hour. I flew the plane for another hour today 3.5Kft at around 2450-2500RPM and full rich, EGT's were around 1365-1400 and CHT's 380-395, oil temp never above 189deg. But I did see the #2 cylinder consistently cooler than the others. When I powered down for the approach, things evened out across the board. I know I have to get used to working with the JPI, but am wondering what anyone else has seen during break-in and having an analyzer. I am concerned about running the engine too hot and glazing the cylinders. Is full rich mixture necessary? Thanks.
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Sounds to me like you flew the new motor just right.... Hopefully your A&P did the same thing yesterday... If he did you are on track to have a long living top end.... The JPI will give you information overload since you are new to all that data.... Look for trends and don't freak out over one cylinder being a bit different then the others, it is mostly a baffle, intake and exhaust difference that makes it show uneven numbers...... Give the plane another 10 hours then change oil and filter...IMHO...

Ben.
 
Tom-D said:
All aviation oil is a mineral base.

there are a few semi synthetic, but no pure lipid oils in aviation use today.
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What do you define as a "lipid oil"?

To me, it sounds like you're describing what are generically called acyl glycerides- esters of glycerol and fatty acids. This group of compounds include vegetable oils and fish oils.

Last time I was at Old Rhineback, those WWI planes were using castor oil as a lubricant (acyl glycerides)- the odor was quite noticeable.
 
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