What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Breakin question

777Dave

777Dave

Well Known Member
Relating to fuel consumption. I am breaking in a zero time O-360, about 7 hours at the moment. CHTs have dropped nicely, oil consumption seems ok as does oil temp at about 195*.
At my engine builders suggestion I have started to lean the mixture but am still seeing high fuel flow at about 11gph.
From experience, can anyone give me some idea when to expect to see more normal consumption?

Thanks
 
The newness of an engine doesn't materially impact fuel consumption.

What power settings are you using (RPM & MP) and how far are you leaning (50' rich of peak, 50' lean of peak...??) when you see the 11 GPH?
 
11 GPH sounds about right for an O-360 at 75% power, according to the operating manual.

You are operating your engine according to the manual?
 
Power

No EMS yet but soon , so I am leaning the old fashioned way.
That is at about 70% power... 23?, 2400rpm.
My A&P figures about 50 hours before it will be fully broken in.
 
50 hours seems like a long time. My O-320 was broken in in far less than that.
Fuel consumption is controlled more by the mixture knob than break in condition.
What are your EGTs doing?
 
I followed the recommendations of our engine guru here at CNC3 for break-in which were to run it rich at 75% power until CHT's and oil consumption stabilized. This took about 12 hrs after which I started varying power settings and began leaning. Since then I typically cruise at around 60% power (2350-2400 RPM) leaned out to peak or sometimes slightly LOP, based on the Dynon and my AF gauge, which indicates around 14.5/1.

Tracking my actual fuel fill ups and flight times over the past 1.5 yrs and 200 hrs since break-in shows a fuel burn of 7 USGPH at my normal 60% power leaned to 14.5 ish AF providing around 148 kt indicated airspeed (RV7, O-360, 85" pitch Sensy).

Hope that helps.

Al
 
I was breaking in at this time last year, but here in Ontario, not Ft. Myers... :)

I ran the first 4 hours full rich. By then CHTs had settled and oil consumption was nearly flat. Continued to run well ROP until 10hrs or so, then started leaning a little more. Can't go LOP with this engine so always stayed ROP and slowly brought temps closer to peak by leaning. After 10 hours the oil consumption was almost negligible (the next quart lasted 24 hours).

Also note that electronic ignitions, if installed, will alter your fuel consumption significantly as compared to the Lycoming power charts for any given power setting.
 
Thanks for the input. I think most of the higher fuel flow is because I am running it harder than I used to run the old engine. It will be interesting to see if there is much change over the next 50 hours.
BTW, Ft. Myers is a great place to break in an engine.😁 in January.

Cheers
 
Dave,

When I broke in my O-360 I was seeing 16 GPH for the first 10 hours.

I was running it WOT, full rich, and staying below 3000' MSL.

Hang in there, it gets better. Now I typically cruise mine at 155 to 160 knots at 7.2 GPH LoP.
 
If you have standard steel cylinder barrels, or nickle plated barrels, your break in at high power settings should be pretty short, 2-3 hours at the most usually. If you have chrome plated barrels, break in can be as much as 50 hours. This according to what I read at Savvy, from Mike Bush. Don?t lean too much during break in. You want to keep your cylinder temps below 440 for a Lycoming. High power helps seat the top rings and shouldn?t take long to do. Once the CHT?s have come down, run the engine like you normally will, including leaning. An O-360 running at 100 degrees rich of peak should probably consume 10.5 gph, maybe a little more. You can download a power chart online to give you a starting point. Your installation may be a little different - higher/lower compression than standard 8.5:1, electronic ignition, etc.
 
777Dave said:
My A&P figures about 50 hours before it will be fully broken in.
Click to expand...

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.
 
rocketbob said:
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.
Click to expand...

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
 
Last edited:
CHTs are good, it?s just fuel flow that seems high in spite of leaning. I?ll see if that improves over time.
 
777Dave said:
CHTs are good, it?s just fuel flow that seems high in spite of leaning. I?ll see if that improves over time.
Click to expand...

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?
 
lr172 said:
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.
Click to expand...

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.

lr172 said:
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.
Click to expand...

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.

lr172 said:
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
Click to expand...

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.
 
Kyle Boatright said:
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?
Click to expand...

Carbureted engine. FlowScan fuel flow meter that was used with the old engine.
 
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
 
hot CHTs on new o320

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 said:
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.
Click to expand...
 
Nived17 said:
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.
Click to expand...

Too many variables to sort thru first to say something definitive but I would be looking to see if you are getting the right fuel flow for your engine at takeoff first. Then look at timing and any cooling issues that might exist.
 
CHT

What worked for me in 100 degree plus temperatures: On the fist few flights with new engine I would watch the CHT closely on takeoff, any trending over 400 pull the power back to 25" and level off until 130 kts and then resume climb. After the rings are seated 425 in the climb is not a problem.
10-1 pistons, timing set to 22 degrees for break in. After a few flights the CHT's dropped noticeably.
The 10-1 pistons are pretty common in aerobatic airplanes. Some of the racers run as high as 13-1.
 
We all know this but for the record.
High Power (>75%)
Full Rich
Mineral Oil
Don't baby it or do T&G's.
(observe temp limits)

FF will come down when you lean it after break in. High Alt, below 65% power FF will be at or below 9 GPH, and at 55/55% power at or below 8 GPH. LOP is going to give you better specific consumption, but with Carbs it is hard to do, due to uneven fuel distribution to the cylinders.

When is it break in over? When it is over. I have read with steel cylinders break in can be done in 5 hours, plated cylinders longer. Once break in is done, use regular oil and you can fly it anyway you want. The cylinder manufacture has recommendations, follow that.

https://www.lycoming.com/sites/defa...ating engine Break-In and Oil Consumption.pdf

https://www.lycoming.com/content/hard-facts-about-engine-break
 
Last edited:
You must log in or register to reply here.
Back
Top