Running LOP

Running LOP

Walter--(I am sure you will see THIS one):

I am interested in using your LOP recommendations in my 1981 C-172P, Lyc. 0-320, running on 100LL.  Almost every time I run-up prior to take off, one mag has severe missing, which clears up when I burn it off at 2100 RPM by leaning.  Obviously something is happening here, and it can't be too good for valves, plugs, rings, etc.  Please explain, in really simple terms, how to implement LOP operation in my plane from start-up to take-off to cruise to landing to shut-down.  Thanks!

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Re: Running LOP

Have the timing checked.

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Re: Running LOP

Clay,
How does timing affect lead fouling during taxiing ?

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Re: Running LOP

Bob,

It sounds more like a plug that needs to be cleaned rather than operating Lean of Peak in flight.  Especially if this problem has crept up recently.

From the symptoms you describe, it sounds like you're not leaning the engine during ground operations.  This promotes plug fouling.

If your engine has Slick mags, make sure they're inspected every 500hrs.

There are many proponents of Lean of Peak operations...I am not one of them.  The risk of having one or more of the cylinders enter into detonation during Lean of Peak operations is too high.
Detonation can, and will, do serious damage to the engine without the operator knowing it.  Most of the engines which were traditionally operated Lean of Peak were running at less than 65% power *and* had a full time flight engineer monitoring the engines.

Typically to avoid plug fouling, I've the started and idling, I then aggressively lean the mixture to just before the engine starts to falter.  I leave it there until I'm ready to perform the run-up.  After the run-up, I'll lean it out again if I'm not immediately taking off.

Cheers,
RH

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Re: Running LOP

I'll bet you a six-pack of German beer your fouled plug is due to a worn valve guide allowing oil to settle into the cylinder and foul the lower spark plug overnight.  A high-power run-up merely burns the oil off and then the plug begins to fire again.  Replace the offending plug with a fine-wire plug for a possible cheap/temporary fix or replace the valve guide for the long-term fix.

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Re: Running LOP

George,
Interesting observation.  If that is indeed the case, would you expect the plug to be misfiring immediately after engine start-up, so that a run-up right after start-up would have it missing?  I haven't tried it like that yet; only after taxiing for a few minutes.  Thanks for your response!
Bob

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Re: Running LOP

Please allow me to answer several posts at one time.

First, George's idea is a good one.  It could also be oil seeping past a control ring.  Either would cause the observed effect.  Incorrect timing could exacerbate it, but it is doubtful.  Also, we see weak spark plugs, that will pass a bomb test, not work properly when under stress.  Also, a weak harness will make it spit and cough when under stress.  George's explanation makes the most sense of the several possiblities.

It would be impossible to explain ALL of the concepts of LOP operation in one post.  Oh, but were engine management that simple!  For that matter, it would also be impossible to explain all of the nuances of operating ROP in one post.  See John Deakin's articles on engine management on Avweb (www.avweb.com) under the Pelican's Perch set of articles.

Someone else indicated some concern about operating LOP for detonation concerns.  This is a commonly held, often repeated, misunderstanding of the combustion process.  It is all but IMPOSSIBLE to have detonation LOP.  (I'd say it was absolutely impossible, but that would be open to minor debate) We've tried to make an engine detonate LOP and simply CANNOT.  We are currently using the most detonation-prone engine in the GA fleet; the IO-540J2BD.  The most detonation-prone mixture setting is found at about 40dF ROP (very, very close to the mixture of 50dF ROP often recommended!)

Detonation is one of the most often misunderstood events in aviation.  If detonation were not an issue ROP, we would not run our engines VERY ROP during takeoff power; we would run them at 80dF ROP, or BEST POWER.  Doing so will frequently result in light to medium detonation and can progress rapidly to heavy detonation.  Try as we might, we have been completely unsuccessful at creating ANY detonation when LOP--even at FULL RATED POWER.  (We recently presented a program to the FAA concerning detonation which is the reason they are now revisiting their definitions and concepts of detonation.  They are sending a group of FAA experts to our January Seminar.)

We are currently being very unsuccessful at destroying an IOTN-550BB on a Bonanza which has been run 95% of it's life at MORE THAN 85% power, LOP (much of it at more than 90% power).  It currently has 1500 hours on it and at a tear-down at 1000 hours everything was within NEW limits... not servicable limits, but NEW limits.

LOP operation is easier on an engine than ROP operation.  Internal cylinder pressures are lower and CHTs are lower when LOP than  any ROP setting.  The two conditions necessary for detonation are high pressures and high temperatures.  Neither are present when LOP.

There is no known engineering data to the contrary...  Old Wives' Tales notwithstanding. <g>

Walter Atkinson
Advanced Pilot Seminars

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Re: Running LOP

*Please explain, in really simple terms, how to implement LOP operation in my plane from start-up to take-off to cruise to landing to shut-down. *

That would take a book and a few days!  Just like teaching ROP operation, it can't be done that simply... not if you wish to UNDERSTAND it properly.  We're working on Chapter 4 of an engine management book now which we expect to be 300-400 pages when finished???

Sorry.

Now, if you have a SPECIFIC question...

Walter Atkinson
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Re: Running LOP

Walter,
More specifically:
1) Is a "standard" EGT analog gauge of any real use in leaning properly or setting for LOP?  If so, how is it done?
2) My engine sounds rougher on the lean side of peak--is that just my imagination?  Is this bad?
3) How far to go on the lean side of peak?  How to tell?
4) Is full rich only to be used for take-off and climb (full power) in your thinking?
(or in emergencies of course)

Thanks.
Bob

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Re: Running LOP

Bob:

1) Is a "standard" EGT analog gauge of any real use in leaning properly or setting for LOP?  If so, how is it done?

A standard analog EGT guage will work only if you know you have well balanced F:A ratios among all cylinders.  To know this in a carbureted engine you almost MUST have a multiprobe engine monitor.  Also, one other drawback of the analog guage is that leaning with it is sort of like measuring with a micrometer and cutting with a chainsaw.  It's kinda in-exact.

2) My engine sounds rougher on the lean side of peak--is that just my imagination?  Is this bad?

It probably is.  What you are feeling is the difference in HP output between the cylinders which have dofferent F:A ratios and, therefore, are making differnt HPs.  It won;t hurt anytihng and is not bad fo rthe engine, but over the long haul, vibration is not a good thing to be enduring.

3) How far to go on the lean side of peak?  How to tell?

That depends on the power the engine is producing.  The higher the power, the leaner LOP one should be.

4) Is full rich only to be used for take-off and climb (full power) in your thinking?  (or in emergencies of course)

That depends.  As a matter of routine, I use full rich for takeoff and lean to a Target EGT in the climb (you can go to our website to download a freebie on the Home page about leaning in the climb).  ONce in cruise, if below about 9000 feet, I run LOP.  How far LOP depends on the altitude.  If above 10000 feet, if I have a tailwind and/or range is a factor, I run LOP.  If range is not a factor, or if I have a headwind, or for some reason (like being at 16-17000 feet) I need all the power I can get I will run at 80 ROP for Best Power or 50dF ROP for a tad better range than 80dF ROP will give me.

Walter Atkinson
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Re: Running LOP

{George,
Interesting observation. If that is indeed the case, would you expect the plug to be misfiring immediately after engine start-up, so that a run-up right after start-up would have it missing? I haven't tried it like that yet; only after taxiing for a few minutes. Thanks for your response!
Bob}
  Yes, Bob, I would expect it to be oil soaked at startup.   I don't believe the suggestion that an oil-ring problem would cause the symptom as you described it.  An oil-ring problem would manifest itself at the end of a flight as well.  Additionally, it would pretty apparent upon inspection of both upper and lower plugs, and would be accompanied by high oil consumption,...so I don't think that's an expectation since you don't mention those symptoms.
  A fine-wire spark plug is more capable of firing despite oil fouling, and it also is more likely to self-clean in such an environment.  But it's only a temporary fix.

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Re: Running LOP

Walter, I think I'll forget about LOP--sounds too complicated and possibly risky, unless you have all the right sensors, etc., and knowledge of "Df" (whatever that is), etc.  Thanks anyway.
Bob

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Re: Running LOP

Bob,
Regarding "dF"   or Df   whichever...I'm pretty sure that's in referrence to degrees farinhiet   Referrences to 40, 50 and 80dF were puzzling me for a bit...I hope thats correct...
I'm just used to seeing it written as 40ºF...it's pretty universal.
To make the raised circle for the degree symbol, hold down the ALT button then enter 167 on the keypad (not the numbers at the top of the keyboard), release the ALT key and º should appear.  If not...oh well!!
Michael

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Re: Running LOP

*Regarding "dF"   or Df   whichever...*

So many internet forums do not support th degree sign in the text, that I've gotten used to writing ?  as dF  or dC.

Sorry.

Walter

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Re: Running LOP

* I think I'll forget about LOP--sounds too complicated and possibly risky, unless you have all the right sensors,*

OK.  But, you should understand that LOP operation is no more difficult that ROP operation and a LOT safer... not less so.  As a matter of fact, many pilot's run blissfully ignorant ROP and are doing harm to their engines without any knowledge of it whatsoever.  If you screw up the settign LOP, it's SAFER than if you screw up the setting ROP.

KNOWLEDGE is the key, no matter whether your engine is running with extra fuel or extra air in the F:A mix.

A non-conforming engine can run smoothly ROP and that hides problems.

Again, knowledge is the key.

Walter Atkinson
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Re: Running LOP

*   I don't believe the suggestion that an oil-ring problem would cause the symptom as you described it.*

George, please give me the value of your experience.  Would not a weak/broken oil control ring (poor ring tension) allow oil to seep by the rings while the engine is sitting?  That sure is one of the major causes of hydraulic lock in radials.  If this happened, wouldn't it also tend to foul the lower plug?  Wouldn't this disappear during a run-up burn out?

Notice that I did say this wasn't nearly as likely as your suggestion of a leaky valve guide, which I thought to be the most likely.

Walter

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Re: Running LOP

Walter,
If knowledge is the key, then I need to find someone willing to impart a little re. LOP.   So far, all I've seen is, quote from you,

< "That would take a book and a few days! Just like teaching ROP operation, it can't be done that simply... not if you wish to UNDERSTAND it properly. We're working on Chapter 4 of an engine management book now which we expect to be 300-400 pages when finished???>

I guess I'll wait on the paperback version.  smile

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Re: Running LOP

Bob,

me too...

I've browsed the threads and it seems that you and others are convinced that oil fouling of the lower plugs is the problem.   I assume you've pulled the plugs, as suggested in one of the threads, and confirmed the problem is oil fouling.

I've read about the type of symptom you described but it is caused by the beginnings of a sticking valve rod in the guide.  The engine appears as if its misfiring immediately after startup, but smooths out after it runs for a while.  I've read into your description of the run-up, which gives it time to settle out (early sticking).  The problem is that this kind of early detection by this sympton is key in preventing you from having an inflight engine failure.  Bottomline, I suggest if you haven't already done so, check the plugs for oil.  If you don't have "sufficient fouling", or they don't look bad as compared to an upper plug, then the cause could be something else.

my two cents...

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Re: Running LOP

Bob:

* If knowledge is the key, then I need to find someone willing to impart a little *

Gee, Bob, I've been more than willing to answer any question you or anyone else has posed.  To simply ask for ALL that I know about operating LOP in one post is a little tough for me to accomplish.  There simply isn't the bandwidth.  It would be like asking my college professor, "In simple terms, in a few paragraphs, tell me about 'physics.'" 

That answer about LOP would look like this:

"Operating LOP is using the right half of the engineering mixture chart."  Yeah, I know, not particularly responsive to the uninitiated.  First we must make the student knowledgeable of the chart referenced.

As I said earlier, I'll try to answer any specific question that you have which is answerable in this forum format. You might begin your educational trek by reading John Deakin's articles on engine management on AVweb. <http://avweb.com/news/columns/182146-1.html> is the link to ALL of John's articles.  These are the articles we suggest our students read before coming to class.

If you are truly interested, I can FULLY educate you over one weekend.  We will be discussing piston engine management issues ranging from mixture management to detonation, when to be ROP and when to be LOP and why, HP calculations, using and understanding engine monitors, RPM and MP issues, and saving  money on maintenance by understanding the engine, how to best achieve longevity in a piston engine and what you can do to avoid being caught away from home with a mechanical problem.  We will show REAL, in-flight emergencies and discuss the appropriate actions.  We will show--on a live-running engine--the effects the pilot has on the engine with the prop, throttle and mixture controls.  Those are usually quite a surprise to the student who has never seen these effects on the combustion process.

In the class we are having in January, there will be several participants from the FAA.  Their interests vary from detonation, engine certification, and even the division which writes the test questions for the A&P test!  I have been asked to review and make suggestions concerning improving the quality and accuracy of the test questions concerning piston engine operation and management.

There was an article in the Cessna Owner Magazine, written by Kevin Knight, a few months ago about this class.  Sorry, I don't remember which Month.  If you are interested, you might visit <http://advancedpilot.com/explore_001.htm>

Repsectfully.

Walter Atkinson
Advanced Pilot Seminars

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Re: Running LOP

Walter,
Thanks for the links--I will do some reading.  I don't have the time to attend classes on the matter but any info. you or others can impart  re. ways to better manage engine operations will be appreciated, by me and I'm sure anyone else who reads the posts.  Thanks.
Bob

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Re: Running LOP

Barry,
Thanks for the advice--I am going to test for roughness immediately after startup, then after running up with no leaning, and then after leaning.  This should tell me something, but I also plan to pull the plugs and take a look at them.  My first reaction was "it's just lead fouling", but your response and others have pointed to other more insidious possible causes.  So I intend to rule them out.  Thanks to everyone for their posts!
Bob
(and I will post my results)

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Re: Running LOP

Walter,
Just took a quick look at your GAMI web site, and got the distinct impression that operating LOP is a concept that works best (read "safest") if you have a fuel injected engine (preferably GAMI's?), and also a multi-probe LCD EGT gauge.  Is this a correct assumption? 
Something tells me carbureted engines with a single probe analog EGT (like mine) are not meant for this type of experimentation.
Bob

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Re: Running LOP

Bob:

Please allow me to clarify a few issues:

1) I do not work for nor have any business relationship with GAMI-not that it matters.  <g>

2) Engines run LOP must have very even F:A ratios to all cylinders or they will feel rough.

3) Historically, that was accomplished in carbureted engines (radials).

4) More recently that has been accomplished in injected engines by balancing the F:A ratios with GAMIjectors in those engines with poor factory injector F:A ratios.

5) Approximately one year ago, I discovered how to do this effectively in a 182.  I have been flying that 182 LOP since.  It is carbureted and has an EDM-700 JPI.  Since that experience and improvement in my understanding, I have flown several non-engine monitored 182s LOP with success.  It's a little tougher since having the experience in an instrumented airplane helps a lot.

6) I have received multiple e-mails from other 182 and 172 (as well as carbureted Pipers) pilots reporting this same success.

Walter Atkinson
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Re: Running LOP

Walter,
Thanks for the further clarification.  I guess the bottom line is I don't want to try LOP if it means a rough running engine, plus not having accurate instrumentation to measure temps. is another factor.  But thanks for the information--if I ever buy a fuel-inj. a/c, maybe it would be a different story.
Bob

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Re: Running LOP

Bob:

Do you have a carb temp guage?  If so, most 182 drivers who are ruinning LOP set the carb temp to 10?C and it better vaporizes the fuel to get good F:A ratios and it runs smoothly LOP.

Try it and let us know how it works in your airplane.

Walter

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