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When can I start to lean during break-in?

ao.frog

Well Known Member
I've just performed the first oil change on my brand new Lyc IO-360, and it was a relief to find that both the oil-screen and the oil filter has no abnormal deposits, nor dind I find any screws, washers or nuts in them... hehe...

The oil consumption has decreased about 50% for every flight up until now:
First flight: 1 hr: oil consumption 0.5 litres
2nd: 1 hr 10 mins: oil 0,3 litres
3rd: 1 hr 40 mins: oil 0,2 litres
4th: 1 hr 10 mins: oil 0,1 litres

I'm flying at 75% and 65% power for now, varying power every 15 mins according to Lyc SB 1427C dated Des 29, 2010 where it says:

For correct piston ring seating, in a top overhauled engine or a newly overhauled engine, operate
the aircraft at 65% to 75% cruise power until oil consumption is stable.


Up until now, I've flown at mix full rich and the CHT's are around 350*F. No sign of CHT drop yet. (5,1 hrs tach)
I'm flying beetween 2000' and 2500' MSL and the OAT is 5-8*C at that altitude these days (Spring has just arrived here)

I'm wondering when I can start leaning?
I haven't found anything in the SB about when to start leaning during breakin, but here on the forum, (http://www.vansairforce.com/community/showthread.php?t=75132) I found that at 75% I can lean to about 180*F ROP and at 65% I can lean to 100*F ROP.

I guess this numbers are for an engine already broken in, so it'd be nice to know when or if I schould lean to these numbers during breakin?

CHT's must ofcourse be kept below 400*F at all times, and with that in mind: when can I start leaning?
Or schould I continue flying at full rich until CHT drops (guess around 10 hrs?) and oil consumption is stable and normal?
 
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At an airport altitude of 4600' msl, I was leaning my new Lycoming on day one. Too much power loss without, in addition to fouled plugs. Worked out very well, when all was broken in. Never ran full rich, except for startup..........and was immediately leaned at that point.
 
I am from the camp that it doesn't matter. I started running LOP with my new engine from the start.
 
When I was breaking in my IO-540 Barrett engine, Allen said I could start running LOP after 15 hours. Temps came down at 10-12 hours as I recall.

Jim Berry
RV-10
 
This just proves once again.....engine break in is done in the first 5 hours.

You can and should break in your engine either (A) Full Rich and keep it above 75% or (B) WOT-28"/2500+/80dF LOP provided the engines F/A ratios are good enough.

Enjoy your engine, go fly it!

PS: This applies to a simple O-320 or a Turbo IO550, ;)
 
Forget oil consumption. The tell tail is the lower spark plugs. I break engines in all the time and have found over the years that running 75% or higher until the lower plugs are completely dry is the ticket.. Do not remove the break in oil for the first 50 no matter what. Once the break in oil is out, the break in stops. If it is not complete, you can not restart it. You cannot run the engine hard enough during the first 10-15 hours. Good luck. Terry
 
Forget oil consumption. The tell tail is the lower spark plugs. I break engines in all the time and have found over the years that running 75% or higher until the lower plugs are completely dry is the ticket.. Do not remove the break in oil for the first 50 no matter what. Once the break in oil is out, the break in stops. If it is not complete, you can not restart it. You cannot run the engine hard enough during the first 10-15 hours. Good luck. Terry

I agree fully with running hard. Common advise is "run it like you stole it." The worst thing you can do is baby a new engine. Babying it will reduce warranty claims (why mfg's required it), but will hurt longevity and a quality ring seal. A good ring seating will reduce blowby and oil consumption. Not to say you can't get a good seal with lower power, but your chances are much less.

You want to run on the rich side, especially the first hour. The extra fuel helps wash the oil off the cylinder walls for better initial break in. I intend to run mine rich for an hour and then lean as appropriate but will run ROP for 10 hours. Millions of cars start their life every year and run lean from the first turn of the key. However, engine cylinders are honed differently. The rings often seat in the first few minutes. As shown by the original poster, this is not the case with the honing used on aviation cylinders.

My experience is all automotive engines, but the metallurgy is pretty much the same.

Larry
 
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I have 11 on my O-320 with fixed pitch prop and max rpm being 2600 to suit the prop.
Temps have just come down a bit, but I cannot understand the fact that in those 11 hours I have to add only 200ml of oil and it could possibly take another 200 now. I have leaned a bit on the ground and when running with reduced throttle in descent, mainly to prevent plug oiling, although the plugs now look good.
Just can't understand the oil non usage.
 
break-in

Remember all aircraft engines are not the same and do not break-in the same. There is a big difference in the break-in time between for example a stock steel Lycoming cylinder overhauled IAW the Lycoming direct drive manual, a Cermichrome cylinder with iron rings, and an ECI experimental Nickel Carbide with moly rings. Russ
 
My engine rebuild is the same. I have used less than a half a quart in 11.7 hours. It's almost scary. It makes me feel like nothing is getting oiled. :)

I used a quart every 10 hours before the rebuild.

I have 11 on my O-320 with fixed pitch prop and max rpm being 2600 to suit the prop.
Temps have just come down a bit, but I cannot understand the fact that in those 11 hours I have to add only 200ml of oil and it could possibly take another 200 now. I have leaned a bit on the ground and when running with reduced throttle in descent, mainly to prevent plug oiling, although the plugs now look good.
Just can't understand the oil non usage.
 
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