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Does low power ops hurt engine ?

Larry DeCamp

Well Known Member
I tend to cruise my 0320 / 7:1 around 19"/2300 RPM / 150 Mph. My carson speed is about 135 mph. The engine is new with 50+ hr. I am concerned that there is a downside for the engines health. I never use full power on the little -3B. What say you engine experts ?
 
My experience

Hi Larry,

For local sight seeing, I run my O-320 at 20in/2080 rpm/150mph all the time(over 50% of the time). I now have over 1650 hrs and she runs great. I pulled a cyl to replace an Exh valve last month, and I replaced the mech fuel pump a while back, but I'm sure these were caused by running LOP on mogas........and not low power ops;)

Just one guy's experience.
 
So long as you reach "normal" operating temperatures and don't find yourself running too cold somehow, I don't see what it could hurt?

Do you know your CHT's and oil temp?
 
If the engine is already broken in, and oil consumption has stabilized (low oil consumption), you are good to go!
2300 with a fixed pitch prop is probably about 2300/23", so that is about perfect, I would think.
As long as the oil temperature is warm enough...
 
Thanks for input

Oil temp runs about 170F. And I lean to about 75 ROP on Mogas. I was just concerned that the low cylinder pressures may cause premature ring carbonizing or glazing OR ? .
 
That oil temp could be low, depending on how it's measured. You need to boil off water, so reach at least 212F. Depending on where your sensor is, it could be you're measuring a lower temp than actually reached in the engine, or you could have a problem of not running hot enough.

Not sure about cylinder pressure issues ...
 
No, it does not hurt the engine.

If it did, Vlad's engine would be toast by now. That is how he cruises.

I do it much of the time also.

:) CJ
 
Water, oil, heresy

That oil temp could be low, depending on how it's measured. You need to boil off water, so reach at least 212F. Depending on where your sensor is, it could be you're measuring a lower temp than actually reached in the engine, or you could have a problem of not running hot enough.

Not sure about cylinder pressure issues ...

I admit to being a heretic about this but why would you think that water won't evaporate at 170; why would you think it needs to boil? Also, that number for boiling is altitude dependent. Also, the oil that is lubricating the cylinder walls is almost certainly a lot hotter than that so, as noted, sensor position and accuracy are relevant. Hotter oil is not necessarily a better lubricant, especially with respect to those areas where viscosity is the property that provides the lubrication such as cushioning main connecting rod bearings.

http://www.engineeringtoolbox.com/boiling-points-water-altitude-d_1344.html

My additional heretical point is one I've made before. The engine is pumping out vast quantities of very humid air at high temps and when the engine shuts down it will have condensation in the airspace inside the crankcase. The important thing is to have a dehydrator for when the engine is NOT running. I have no financial interest in any such product so take this as disinterested advice in the ethical meaning of the term.
 
My additional heretical point is one I've made before. The engine is pumping out vast quantities of very humid air at high temps and when the engine shuts down it will have condensation in the airspace inside the crankcase. The important thing is to have a dehydrator for when the engine is NOT running.

Yep. I have had a problem with rusty cylinders/cams so I always blow the moisture out of the engine for a minute or so with an air-mattress pump. On a winter day it will blow visible moisture out the breather for half a minute. Then I put a homemade dehydrator on the engine.

Lycoming says 180 is the ideal temp. You will still see moisture on shutdown. I hope it helps. Hard to quantify.
 
Does it Hurt the engine

Water will evaporate at Temps way lower than boiling temp and
Water vapor will tend to move rapidly between high humidity to low humidity.
Hang a towel out on the clothes line.
The time the engine runs at operating tempeture is more important
The vapor pressure of water at 75 degrees is .04298, at 150 degrees is
3.7180 and at 212 is 14.696 sea level
Even a cup of water sitting out on the kitchen table will evaporate in 24days
Way quicker if at a higher altitude
Amazing what you can find in chemistry papers
I run mine at 1600 rpm 100 mph. And 120 degrees with dissimilar aircraft and
Usually 110 degrees over OAT at Cruise
I'll get out the popcorn. Cheers
 
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Good point on the evaporation vs. boiling point. Whatever temperature will help get the moisture out of the oil and engine is fine.

Here is what Lycoming says in their operator manual (for O-320 and 360 at least)

OPERATING CONDITIONS
Average *Oil Inlet Temperature
Ambient Air Desired Maximum
Above 80?F 180?F (82?C) 245?F (118?C)
Above 60?F 180?F (82?C) 245?F (118?C)
30? to 90?F 180?F (82?C) 245?F (118?C)
0? to 70?F 170?F (77?C) 245?F (118?C)
Below 10?F 160?F (71?C) 245?F (118?C)
* - Engine oil temperature should not be below 140?F (60?C) during continuous operation.

So it sounds like 170 would be on the low side ...

I could not begin to argue about why those numbers were selected ... but at least it's not boiling point!
 
Oil temp runs about 170F. And I lean to about 75 ROP on Mogas. I was just concerned that the low cylinder pressures may cause premature ring carbonizing or glazing OR ? .

At the low power setting you mentioned you are using, ROP will probably not hurt anything but it is not helping anything either (just causing your fuel cost per flight hour to be higher).

The danger is if you begin using that practice at higher power settings.

A good read on engine leaning -

https://www.jpinstruments.com/wp-content/uploads/2013/05/Mike-Bush-Red-BoxRed-Fin.pdf
 
Oil temp runs about 170F. And I lean to about 75 ROP on Mogas. I was just concerned that the low cylinder pressures may cause premature ring carbonizing or glazing OR ? .

You could put a thermocouple in the sump to see what the general temps are, remember we measure the temp after the oil cooler - more representative of oil-to-bearing-temperature. Important for oil film thickness on the rod journals.

Low head and cylinder temps, within reason, will simply extend the life. Higher ring land temps result in more carbon. Diesels , for example, run quite cool, but don't have the water issue that otto cycle engines have. For them, coolant and oil temps of 180F yield quite long life. Sub cooling in sub zero winter conditions are bad, but TMI for this question here.

I am a big believer in dehydrators - recently a friend measured 3-4 tablespoons of water condensed from a recently run engine. It might be possible to just quickly purge the crankcase of high dew point air on shutdown alone, but a dehydrator will certainly do that and more.

In theory H Evan is has a good point, but Lycoming provides something simple to keep out of trouble. We just don't want crankcase temps to operate below the dew point of the blow by gasses.
 
I loosen the dipstick and let it hang on the edge of the filler neck, allowing the moisture to escape the engine. Seems to work well.
 
Very interesting...

Personally I run my conti IO-360 at about 45% all the time. Then again 100 hours on a 300 h engine is not going to tell me what this will do in the long run. I choose this setting bc it will give me the greatest range...

Running Avgas and leaning till rough and enrich till smooth. No engine monitor. At the low power setting I assume I cannot hurt anything. Also I figure less rpm will always be easier on material?

I loosen the dipstick and let it hang on the edge of the filler neck, allowing the moisture to escape the engine. Seems to work well.

A buddy of mine with 9a and an o320 does this. However a physics professor out at the airport told me that that would make things worse. Any actual data or explanation on this? How do you guys blow out the humid air?
 
I vaguely recall that, at lower power settings, there is an issue with the compression rings not having sufficient pressure on them, resulting in them "skating" on the cylinder walls and the cylinder might also experience ring flutter
 
How do you guys blow out the humid air?

By flying the plane at least once a week....a frequently flown plane is a happy plane. :)

Dipstick stays in place, sure don't want our soupy Alabama air being sucked into the crankcase......
 
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blow it out your..

By flying the plane at least once a week....a frequently flown plane is a happy plane. :)

Dipstick stays in place, sure don't want our soupy Alabama air being sucked into the crankcase......

I hope this is meant as a joke. The air in the crankcase is so humid it will yield precipitation when it cools. Each time you fly.

While a frequently flown plane is a good idea, the oil has mostly run off the parts by a week's time and the water in the air inside the engine has long since run into the oil or at least beaded on the internal surfaces.

Use a dehydrator or not - personal choice - but the results of that choice are not really debatable. Even in Alabama.
 
I hope this is meant as a joke. The air in the crankcase is so humid it will yield precipitation when it cools. Each time you fly.

While a frequently flown plane is a good idea, the oil has mostly run off the parts by a week's time and the water in the air inside the engine has long since run into the oil or at least beaded on the internal surfaces.

Use a dehydrator or not - personal choice - but the results of that choice are not really debatable. Even in Alabama.

I was serious.

I realize you are a vocal and strong proponent of using a dehumidifier. My personal experience leads me to the non-debatable conclusion it has not been necessary for my engines (and many engines in our local community with which I am familiar).

I also use a sump heater 24/7 for four months of the year. ;)
 
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i have to wonder how much water these driers will pull until they need to be dried. i can see how they would be effective in a new sealed engine where they are pulling water from the air at 60% relative humidity when it was trapped in the engine . this is way different trying to regularly dry air that is water saturated as a product of combustion.
i would be curious to know the weight ratio of chemical to water weight before it is saturated.
i did look all this up once for the units that were supposed to dry a room and the results were dismal considering the considerable weight of water in the air in a room.
 
please see new thread on dehydrators

i have to wonder how much water these driers will pull until they need to be dried. i can see how they would be effective in a new sealed engine where they are pulling water from the air at 60% relative humidity when it was trapped in the engine . this is way different trying to regularly dry air that is water saturated as a product of combustion.
i would be curious to know the weight ratio of chemical to water weight before it is saturated.
i did look all this up once for the units that were supposed to dry a room and the results were dismal considering the considerable weight of water in the air in a room.

You don't have to wonder how much, just monitor the color of the indicator beads. Just to clarify, they don't "pull" air from inside the engine. Rather, they push dry air in. Ambient air varies a lot with location, season and immediate WX. A room is a large volume of air so perhaps not a comparable case. The exchange of air is low volume and the positive pressure is weak but sufficient.
 
Serious thread drift

I was hoping to hear more about weather or not the use of low power settings
hurts your engine.
Based on my studies and books written on engine management by Kas Thomas
https://www.amazon.com/Fly-Engine-Kas-Thomas/dp/B005LX4EVM
the use of high power settings does nothing to hurt your Lycoming, quite the contrary as I understand it.
In fact Kas writes extensively about the negative impact on engine health when babying a Lycoming. Particularly the use of anything other than full power for take off, citing the need for combustion chamber pressures
needed to achieve proper ring seating to prevent combustion gas blow-by.
Much the same is true for cruise conditions. As I understand it, if you want your engine to last, use high power settings, if you want your gas to last use low power settings.
What say the experts??
 
I was hoping to hear more about weather or not the use of low power settings
hurts your engine.
Based on my studies and books written on engine management by Kas Thomas
https://www.amazon.com/Fly-Engine-Kas-Thomas/dp/B005LX4EVM
the use of high power settings does nothing to hurt your Lycoming, quite the contrary as I understand it.
In fact Kas writes extensively about the negative impact on engine health when babying a Lycoming. Particularly the use of anything other than full power for take off, citing the need for combustion chamber pressures
needed to achieve proper ring seating to prevent combustion gas blow-by.
Much the same is true for cruise conditions. As I understand it, if you want your engine to last, use high power settings, if you want your gas to last use low power settings.
What say the experts??

Running an engine at low power will not harm it.

I know of one 0360-A4M out of a Cherokee that was flown at 2200 rpm most of its life. It's crank shaft was in new limits at first overhaul. Lycoming Flyer says if you want long engine life, run at 65%.

It does not matter.
 
Lycoming Flyer says if you want long engine life, run at 65%.
Agreed, and I didn't think that 65% power would be "babying".
In fact at cruise altitudes above 8000 an NA engine isn't producing much more than 65% power anyway.

My concerns would be for those who lumber around at 40% as someone mentioned, that simply can't be good based on what I know.
 
Anecdote alert

I have "heard" that those who fly pipeline patrol and fish spotting (at low power settings) tend to have more oil consumption.
 
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