Can running at 65% or less hurt your engine?

N801BH said:
My question to all the A&P's out there...

Personally, when I see the term ( A&P) after a persons signature I assume they are somewhat intelligent in the concept of motors... Maybe I have been wrong all these years in assuming this..:redface:
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I have talk with a few A&P's and I know a he## of a lot more about engines then these guys.

When using a torque wrench I had to tell one the correct way to use it, this scared me to death at the time. I just blew it off as a fluke but then I talked to a couple others and it was not much different. These where young men.

Then I spoke with some older A&P's whom where older then I and they knew their stuff. I would never question nor tell them how to do anything, I ask them how to do things.

I would think an A&P would know the internal combustion engine and how to use the tools needed to work on them. But then I found, no they really don't. No need, they replace parts not repair parts. At least this is my take on it why they know what they do. If they had to get in there and Line Bore or grind some valves they would know a lot more. Nope the replace the complete engine with new and send the old core back.

Myself I say...rebuild that puppy, you then learn what you have...old school thinking, I know.....
 
You don't have to be an engineer or even a mechanic to realize that most engine stress is at high power. Most engine failures happen on take off or climb, not during taxing. The source of the stress are the higher forces and temperatures imposed on the metal that can lead to material failure in crankshafts or cylinders. Have you ever heard of blowing out a cylinder or cranckshaft during taxing?

José
 
From a Lycoming document:

"One of the first considerations of low-RPM cruise is that power settings this low should not be used during the engine break-in period. During the break-in period, normal climb power as specified in the Pilot’s Operating Handbook should be used. To seat the piston rings in a new or overhauled engine, cruise the aircraft at 65% to 75% power for the first 50 hours, or until oil consumption has stabilized. Low power for break-in may result in glazed cylinder walls and high oil consumption that can only be cured by cylinder removal and rehoning."

So is the OP sure that he wasn't referring to a new or freshly rebuilt engine?


And for after break in, it says:

"For maximum service life, maintain the following recommended limits for continuous cruise operation:
a. Engine power setting — 65% of rated or less.
b. Cylinder head temperatures — 400˚ F. or below.
c. Oil temperature — 165˚ F. — 220˚ F."

and for the turbo:

"For maximum service life, maintain the following recommended limits for continuous operation.
a. Engine power setting — 65% of rated or less.
b. Cylinder head temperatures — 400˚ F. or below.
c. Oil temperature — 165˚ F. — 220˚ F.
d. Turbine inlet temperature — maintain 100˚ F. on rich side of maximum allowable."
 
And some more low power info from Lycoming's key operations document (I don't recall where I got it):

"There are some other considerations of low-power cruise operation. Low manifold pressures, below an arbitrary point of perhaps 18" for continuous cruise, may cause excessive oil usage and oil buildup in the valve guides which could lead to sticking valves.

Particularly during cold-weather operation, low-power operation may allow both the oil and cylinder head temperatures to fall below the normal range. This is detrimental to good engine health. Oil temperature in particular should be maintained between
165˚ F and 220˚ F to achieve maximum service life. At lower temperatures, the moisture which gathers as a result of combustion will not vaporize and be expelled. This can cause dilution of the oil which detracts from its lubricating properties.

Quite frequently, someone will ask if the engine will last longer if it is run at a slower RPM setting. The answer must be qualified. Operation at the recommended cruise RPM settings should allow the engine to reach TBO if it has regular oil changes, is operated within normal temperature ranges and is well cared for by pilots and maintenance personnel. Longer engine life may be expected from most engines when the operator is willing to sacrifice maximum performance for conservative cruise operation in the 60% to 65% power range. For many engines, these power settings are achieved at 2100 or 2200 RPM rather than the 1800 or 1900 RPM mentioned earlier in this discussion."
 
I've noticed that it's fairly difficult to get all the cylinders on a 182 below 400 degrees. On the one I was flying on Wednesday, it didn't seem possible to get any of the cylinders below 400 at 75% power. It wasn't that hot a day, either.

I suppose I could have opened the cowl flaps in cruise, but I opted to reduce the power setting and enrichen the mixture instead, because I've heard that cooling the cylinders with air flow doesn't deal with the issue of high internal pressures. Maybe next time I'll try LOP. Many Skylanes won't run smoothly that way, although I have encountered some that will.
 
skidoo said:
From a Lycoming document:


So is the OP sure that he wasn't referring to a new or freshly rebuilt engine?


And for after break in, it says:

"For maximum service life, maintain the following recommended limits for continuous cruise operation:
a. Engine power setting — 65% of rated or less.
b. Cylinder head temperatures — 400˚ F. or below.
c. Oil temperature — 165˚ F. — 220˚ F."

and for the turbo:

"For maximum service life, maintain the following recommended limits for continuous operation.
a. Engine power setting — 65% of rated or less.
b. Cylinder head temperatures — 400˚ F. or below.
c. Oil temperature — 165˚ F. — 220˚ F.
d. Turbine inlet temperature — maintain 100˚ F. on rich side of maximum allowable."
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OP here. The presenter made no reference to "break-in" power settings. In fact, my cylinders were broken in about 1700 hours ago. Skidoo, if you know which Lycoming document the above information came from, I could share it with my airplane partner. Hard documentation should help in swaying him to not follow the recommendations made by the presenter.
 
Well, in my 13,000+ hours, I have noticed;
Running at 75% gives the engine better and more uniform cooling. More air through the cowling. That's only if the flexible baffle seals are in good shape, and facing the right way when you drop down the cowling. And the metal baffles do not have any unplugged holes. I have operated ASEL and C421 way over TBO without changing cylinders.
Leaning! More depends on the individual cylinder's, engine timing is correct, correct spark plugs, if your engine gauges are correct. In fuel injected engines, all the above plus; Fuel injection nozzles air clean, and spray the right pattern. And no dents, bends, or blockage of injector lines.
In turbine, we actually test the nozzles regularly. :yes:
 
Steve Job said:
OP here. The presenter made no reference to "break-in" power settings. In fact, my cylinders were broken in about 1700 hours ago. Skidoo, if you know which Lycoming document the above information came from, I could share it with my airplane partner. Hard documentation should help in swaying him to not follow the recommendations made by the presenter.
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I can't easily get the link because it is a pdf file. But it is there if you do a search for "lycoming flyer operations".
 
skidoo said:
And some more low power info from Lycoming's key operations document (I don't recall where I got it):

"There are some other considerations of low-power cruise operation. Low manifold pressures, below an arbitrary point of perhaps 18" for continuous cruise, may cause excessive oil usage and oil buildup in the valve guides which could lead to sticking valves.
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18" MP is going to be well below 65% power in any light plane piston engine, so this paragraph is not relevant to the question the OP asked.
 
N801BH said:
How many people attended that Wings seminar ?

Did no one stand up and question the presenters facts ?

:dunno::confused:
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Nope (including myself). Maybe 6-7 pilots were in attendance, most of them carefully taking notes. I know a twin Commanche and Bonanza pilot were there, not sure what the others were flying. I knew what he was saying was contrary to everything else I had learned from other sources, but I'm certainly no A&P, so I decided to check it out later. Call me a sheeple.:wink2:
 
Palmpilot said:
I've noticed that it's fairly difficult to get all the cylinders on a 182 below 400 degrees. On the one I was flying on Wednesday, it didn't seem possible to get any of the cylinders below 400 at 75% power. It wasn't that hot a day, either.

I suppose I could have opened the cowl flaps in cruise, but I opted to reduce the power setting and enrichen the mixture instead, because I've heard that cooling the cylinders with air flow doesn't deal with the issue of high internal pressures. Maybe next time I'll try LOP. Many Skylanes won't run smoothly that way, although I have encountered some that will.
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Which engine -- the Continental on the older 182's or the Lycoming on the newer ones? A continuous CHT of over 400F on the Continental O-470, with its much lower CHT limit compared to the Lyc O-540 on the later 182's is asking for trouble, and immediate steps to resolve the situation are essential. As for "high internal pressures," if you were operating the engine at 75% with the MP/RPM combination within the recommended range in the POH should not be causing that, and enriching the mixture while reducing power would be asking for plug fouling.
 
Ron Levy said:
Which engine -- the Continental on the older 182's or the Lycoming on the newer ones? A continuous CHT of over 400F on the Continental O-470, with its much lower CHT limit compared to the Lyc O-540 on the later 182's is asking for trouble, and immediate steps to resolve the situation are essential. As for "high internal pressures," if you were operating the engine at 75% with the MP/RPM combination within the recommended range in the POH should not be causing that, and enriching the mixture while reducing power would be asking for plug fouling.
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I've noticed the problem on both Q and S models at 75% power. Wednesday's flight was an S. If I find that it won't run smoothly LOP, then I guess I'll just have to go ahead and open the cowl flaps. I presume that would at least deal with the issue of high temperature weakening the metal.
 
Palmpilot said:
I've noticed the problem on both Q and S models at 75% power. Wednesday's flight was an S.
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Lycoming engine, with the 500F CHT limit. From Lycoming:
"...the engines have benefitted during continuous operation by keeping CHT below 400F in order to achieve best life and wear of the powerplant. In general, it would be normal during all year operations, in climb and cruise to see head temperatures in the range of 350F to 435F."
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So, if it's only a bit above 400F in the S-model, it's not the best, but it's not a disaster, either.
 
Capt. Geoffrey Thorpe said:
You generally don't lug an engine in an airplane because you don't have a transmission connected to wheels connected to the ground. If you push the black knob in, the engine speeds up. If you have a constant speed prop, you can slow it down a bit - but running less than 65% power does not (or should not) imply running at wide open throttle and pulling the prop until you get down to 1000 rpm (assuming that is even possible).
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To a certain degree you can "lug" an aircraft engine (but within the POH). I'm talking over-squared operations with a CV prop. Done right, it's actually a good way to increase MPG due to lower frictional losses. No magic... it's actually in black and white in the engine's POH.

The IO-540C4B5 POH allows operation down to 1800rpm at 55% power up to 25" of manifold pressure. Compared to more "conventional" power settings (higher RPM) you can save up to 1 gal/hr operating in this manner.

For best volumetric efficiency, you always want to be running wide open throttle (WOT). You control your power with the mixture control (presuming LOP operations).
 
Jeff K said:
To a certain degree you can "lug" an aircraft engine (but within the POH). I'm talking over-squared operations with a CV prop. Done right, it's actually a good way to increase MPG due to lower frictional losses. No magic... it's actually in black and white in the engine's POH.

The IO-540C4B5 POH allows operation down to 1800rpm at 55% power up to 25" of manifold pressure. Compared to more "conventional" power settings (higher RPM) you can save up to 1 gal/hr operating in this manner.

For best volumetric efficiency, you always want to be running wide open throttle (WOT). You control your power with the mixture control (presuming LOP operations).
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That hardly qualifies as lugging and is nowhere close to what you can easily do in a car with a manual transmission to cause mechanical problems.
 
Ron Levy said:
Lycoming engine, with the 500F CHT limit. From Lycoming:
So, if it's only a bit above 400F in the S-model, it's not the best, but it's not a disaster, either.
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Has Lycoming found a way to alter this chart?

pp18n.jpg


http://www.avweb.com/news/pelican/182084-1.html

Pratt & Whitney seemed to agree that it's not a disaster, but made it clear which they preferred:

"The lower limiting temperature (450° F) is the maximum for continuous operation. It should never be exceeded except under the restricted operating conditions mentioned in the previous paragraph. It is sound practice to hold the cylinder head temperature 50° F (30° C) below this limit to keep the cylinder head materials at high operating strength."​
 
Capt. Geoffrey Thorpe said:
That hardly qualifies as lugging and is nowhere close to what you can easily do in a car with a manual transmission to cause mechanical problems.
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So one question I've had on this that maybe you know more about. It seems that many GM transmissions are programmed to run at really low engine speeds (1000-1500 RPM) with load on them and have been back to the 700R4. Not being much of a lube system guy, I've wondered what they've done towards that not qualifying as lugging.

In my manual transmission car (which runs about 15 PSI of boost) I typically try to run above 2,000 RPM whenever I'm producing any boost. But the Mitsubishi 6G72 is known for being hard on its main bearings anyway, and at 166k on the clock the oil pressure isn't what it should be, especially on a hot summer day in spite of a new oil pump and upgraded oil cooler. I've considered replacing the rod and main bearings to help this, but since the mains are usually hit harder and dropping the crank is, well, hard, I've not done it yet.
 
Palmpilot said:
Has Lycoming found a way to alter this chart?

pp18n.jpg


http://www.avweb.com/news/pelican/182084-1.html

Pratt & Whitney seemed to agree that it's not a disaster, but made it clear which they preferred:

"The lower limiting temperature (450° F) is the maximum for continuous operation. It should never be exceeded except under the restricted operating conditions mentioned in the previous paragraph. It is sound practice to hold the cylinder head temperature 50° F (30° C) below this limit to keep the cylinder head materials at high operating strength."​
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Well, when you look at the reliability of factory Lycoming cylinders compared to aftermarket or Continentals, it should be pretty obvious that Lycoming cylinders handle the heat better than the competition.

That's not saying that you don't want to run cool. I aimed for 380F in my Aztec just like in the 310. But if I could put factory Lycoming cylinders on the 520s in the 310, I absolutely would.
 
Ted DuPuis said:
Well, when you look at the reliability of factory Lycoming cylinders compared to aftermarket or Continentals, it should be pretty obvious that Lycoming cylinders handle the heat better than the competition.

That's not saying that you don't want to run cool. I aimed for 380F in my Aztec just like in the 310. But if I could put factory Lycoming cylinders on the 520s in the 310, I absolutely would.
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Thanks for the info. I had no idea.
 
Ron Levy said:
The numbers vary with alloys, and we have no idea what alloy about which P&W was speaking.
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Yeah, given the apparent superiority of Lycoming cylinders that Ted reported, that might explain it.
 
Palmpilot said:
Yeah, given the apparent superiority of Lycoming cylinders that Ted reported, that might explain it.
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I've never figured out what exacly is different, I just know that. Lycoming does nitride their cylinders, which is probably a significant part of it as the other makers do not. Also, a heat measurement isn't a heat measurement. Locations will give you different readings. When certifying a new cylinder design, the instrumented cylinder looks like a Frankenstein monster with all kinds of thermocouples all over it.
 
all that "lugging" means is that the engine is running on it's maximum power curve (also called a lug curve) at an rpm lower that rater power rpm. In other words, if your lycoming has a constant speed prop and has a dataplate specifying rated power at 2700 rpm, and you select an operating point of WOT and 2500 rpm, the engine is "lugged". Every engine with a constant speed prop is operated "lugged" on every flight.
 
Ron Levy said:
Which engine -- the Continental on the older 182's or the Lycoming on the newer ones? A continuous CHT of over 400F on the Continental O-470, with its much lower CHT limit compared to the Lyc O-540 on the later 182's is asking for trouble, and immediate steps to resolve the situation are essential. As for "high internal pressures," if you were operating the engine at 75% with the MP/RPM combination within the recommended range in the POH should not be causing that, and enriching the mixture while reducing power would be asking for plug fouling.
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I typically run 2000 rpm, 26" MP, and leaned to maximum TIT. I have over a years worth of engine data about 200 or so hours, and never have been higher than about 380F in looking at the data for CHT.
 
If you are much above 7500' how are you going to run your engine at 75%

Guy is an idiot.
 
Ron Levy said:
Turbo/supercharger? :dunno:
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again, why would anyone run a turbo below 65% up high?

Yes, turbo'd airplanes can run up there - it was obvious the OP, the 'expert' and I were talking about normally aspirated aircraft engines . . .
 
Capt. Geoffrey Thorpe said:
That hardly qualifies as lugging and is nowhere close to what you can easily do in a car with a manual transmission to cause mechanical problems.
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According to the aircraft engine POH it does.... which specifically prohibits Manifold pressures greater then 25" at RPM's of 2000 or below on the IO-540-C4B5. Your modern car has many automatic safety features to prevent you from damaging the engine... your aircraft not so much.
 
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comanchepilot said:
again, why would anyone run a turbo below 65% up high?
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Because you're looking for economy cruise, because piston engines often aren't happy up high and prefer lower power settings, because turbos run out of capability eventually...
 
comanchepilot said:
again, why would anyone run a turbo below 65% up high?
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And because it can extend the range, down to 55% (@ 132kts or 147 kts at 65%) on the T182T up to 20Kft. It extends range down to 45% only to 10Kft. So, if one has a big tailwind, nice... Not so great with a big headwind, so operate at a higher % then, if desired.
 
douglas393 said:
I typically run 2000 rpm, 26" MP, and leaned to maximum TIT. I have over a years worth of engine data about 200 or so hours, and never have been higher than about 380F in looking at the data for CHT.
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Just curious, what does your max TIT settle out to at those settings? According to the Lycoming document referenced earlier, it says for maximum service life, operate TIT at 100 deg rich of the max allowable, which seems to be right at where my TIT falls when choosing most of the POH cruising numbers.
 
skidoo said:
Just curious, what does your max TIT settle out to at those settings? According to the Lycoming document referenced earlier, it says for maximum service life, operate TIT at 100 deg rich of the max allowable, which seems to be right at where my TIT falls when choosing most of the POH cruising numbers.
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And if you go over that, do you get your TIT in the wringer?

{;-)
.
.
 
I think it varies widely depending upon the engine.

You can put me squarely in the camp of WOT almost from chock to chock in my 182 with an O-470. As long as you can keep the cylinders cool (mine never get above 350*F even on a hot day) I truly believe that it's darned near impossible to hurt a 230 HP 0-470.

First, when it's running at 100% power it's already only running at 88% power since other iterations of the exact same engine produce up to 260 HP.

Second, at cruise altitudes above 6,000', which is where I almost always fly, I can't make enough power to hurt it.

So, WOT to altitude and leave it there, adjust prop to 2300 RPM (a bit faster if above 8,000'), lean until rough, enrichen to smooth and I'll be running about 135kts TAS while burning about 11 GPH.

On descent, I simply roll the trim down to 500 FPM. Then slowly back off the throttle to maintain the same MP as I had at cruise. I'll typically enrichen about 5 miles from destination...when I'm going through my first landing check.

I have almost 1,100 hours on my engine (all put on it by me) and the latest oil analysis just came back last week. Blackstone's first sentence read:

TIM: Whatever your strategy is to keep wear low, don't change a thing.
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So, I think I won't.

The only exception to my WOT flying is when I'm going on low & slow $100 hamburger trips. Then I usually fly at about 21"/2,300 and still lean until rough...enrichen until smooth. That's about 65% down low and gets me about 125 kts burning the same 11 GPH.
 
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Tom-D said:
Some times I wonder why the manufacturers spent all the time and money developing the power setting charts and placed them in the POH/OM.
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To sell more replacement parts is about all I can come up with...
 
kgruber said:
Engineers aren't all knowledgeable. Credentials don't always mean anything. If they are presented to you as some kind of proof, RUN!
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I happen to know one of the engineer commentators on this thread has done engine performance and controls work for GM, BMW, and Caterpillar. Credentials enough for me. I don't argue with him about engines and he doesn't try to lecture me on sheet metal.
 
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