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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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 Posted: Tue Apr 20, 2010 12:33 pm Post subject: Excellent treatise on LOP operation |
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With all of the recent discussions on operating Lean of Peak and EGT variation among cylinders I thought it would be useful to post a link to an excellent treatise on the subject, including the fundamentals of 4-stroke engine operation. Those who think they really understand 4-stroke engines well, may be tempted to skip the first part. I suggest you not skip this part no matter how well versed you are on the subject.
http://www.buy-ei.com/Manuals/The%20Pilots%20Manual%20(by%20EI).pdf
If you have already seen and read this, great. If not have fun reading this long but informative article and learning what we all should know to operate our engines properly for long life and efficiency.
Thom Riddle
Buffalo, NY
http://sites.google.com/site/riddletr/a&pmechanix
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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BobsV35B(at)aol.com
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| Posted: Tue Apr 20, 2010 1:59 pm Post subject: Excellent treatise on LOP operation |
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Good Afternoon Thom,
E.I. makes great product and I applaud their effort to spend time and money trying to write something that will help us all operate our engines safer and more efficiently.
Unfortunately, they have taken the bait and made a number of very wrong interpretations of fact. It would take a full fledged engine course to refute or reevaluate each statement in their lengthy narrative, but it is a very poor document.
There is no doubt that when an engine has very poor fuel distribution between cylinders it is going to be difficult to operate well. The E.I products do a fine job of telling the operator just how good that distribution really is.
E.I. spends a lot of time presenting excellent information and then asks engine rebuilders how an engine should be operated. That is a completely irrational method of evaluating the problem.
I agree that most engine shops see a lot of heat damaged engines. If they assume the engines are being damaged because the pilot leaned when he should not have, they are making an unwarranted accusation.
My personal opinion is that a very high percentage of heat damaged engines are seen because the engine is not rich enough during takeoff and other high power operations, but that is rarely because the pilot has intentionally leaned the engine. It is more commonly caused by the engine distribution being so bad that some cylinders ARE operating way too lean or that the fuel system is not providing enough fuel to avoid detonation at the high power settings. Both Continental and Lycoming tell us that you can run at any mixture setting you want when operating at lower power settings. E.I. correctly states that Continental sets that point at 65 per cent power and Lycoming calls for 75 percent.
EI made a gross error when they said that the engine runs it's hottest and that the valves run their hottest at peak EGT.
That is just not true!
The engine runs it's very hottest close to best power. Best power is when you are getting as much power as can be gotten from the amount of air the engine is sucking in. That is close to the hottest place it can run. The actual hottest point is just about 40 degrees Fahrenheit on the lean side of best power, but still about 60 degrees rich of peak EGT.
Once again, completely discussing this whole subject is far beyond what I should be doing here, but I am really saddened that a Company such as E.I. puts out such drivel.
I have been very pleased with every product I have purchased from E.I and their service has been excellent.
They should stick to what they know something about and not present a false interpretation of what has been taught by Taylor and others. LOP operations can make an engine last a LOT longer. The airlines ran their big round engines leaner than Peak EGT for most of the round engines lives. Many of us have several thousand hours behind various big bore engines being operated on the lean side of best power. It works!
Engines last longer and burn less fuel at equivalent cruise speeds. Best BSFC is a good thing and it was hardly mentioned by E.I. Very Sad.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Downers Grove, Illinois.
Lean side operator for almost sixty years.
In a message dated 4/20/2010 3:33:48 P.M. Central Daylight Time, riddletr(at)gmail.com writes:
| Quote: | http://www.buy-ei.com/Manuals/The%20Pilots%20Manual%20(by%20EI).pdf
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[quote][b]
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Tue Apr 20, 2010 3:29 pm Post subject: Re: Excellent treatise on LOP operation |
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Old Bob,
I appreciate your feedback on the E.I. document. I did not catch their error stating the the hottest an engine gets is at/near peak EGT because I already knew that it is much closer to peak power than peak EGT. Common sense will tell you that, and because it is common sense I choose to believe that the statement as you found it was probably an accidental error on their part. Why the editors did not catch that is another question. However, they did not dispute the fact that LOP operation, the primary thesis of the paper, is far better for longevity than near highest power.
I also agree that surveying rebuild shops is not the best way to get the information that they stated they were looking for, but doing that did satisfy another (unstated) purpose which is that ignorant pilots are the cause of most engine longevity problems and therefore every pilot should buy their product. This document, if read and understood by all pilots (errors and all) would go a long way toward reducing the number of pilot induced premature engine overhauls.
With the exception of some errors, either out of ignorance or misinterpretation, or willful misrepresentation (I doubt this), I maintain that the document has some value. Of course, you are free to disagree vehemently with me.
As you noted, different engine manufacturers specify different % power over which LOP is not good for the engine. Jabiru apparently uses 70% power since the jet needle they designed for the Bing 94 begins getting much richer at approximately that power setting, assuming the prop used is within the rpm specs. they recommend.
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
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BobsV35B(at)aol.com
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| Posted: Tue Apr 20, 2010 4:18 pm Post subject: Excellent treatise on LOP operation |
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Good Evening Thom,
Not only will I not disagree vehemently, I will agree completely.<G>
I think it is great that they bothered to publish what they did, I just wish it contained more balanced recommendations. There is a lot of good information there for those who wish to study it carefully.
I really like E.I and regularly recommend as well as use their products.
Until we get electronic fuel flow and ignition systems that can handle it all, it is up to we aviators to understand what is happening.
The best short course on engine management that I am aware of is the one presented by some associates of Tornado Alley Turbo. (The folks who make the factory installed turbo for the Cirrus) They teach a two and a half day weekend course that is outstanding. The same course is available in a self study mode, but attending the course with a bunch of eager aviators is a lot more fun!
As a very minor point, if we can get enough turbo charging, it is possible to run lean of peak safely at powers of 90 percent or more!
As Always, It All Depends!
Happy Skies,
Old Bob
In a message dated 4/20/2010 6:30:33 P.M. Central Daylight Time, riddletr(at)gmail.com writes:
| Quote: | --> JabiruEngine-List message posted by: "Thom Riddle" <riddletr(at)gmail.com>
Old Bob,
I appreciate your feedback on the E.I. document. I did not catch their error stating the the hottest an engine gets is at/near peak EGT because I already knew that it is much closer to peak power than peak EGT. Common sense will tell you that, and because it is common sense I choose to believe that the statement as you found it was probably an accidental error on their part. Why the editors did not catch that is another question. However, they did not dispute the fact that LOP operation, the primary thesis of the paper, is far better for longevity than near highest power.
I also agree that surveying rebuild shops is not the best way to get the information that they stated they were looking for, but doing that did satisfy another (unstated) purpose which is that ignorant pilots are the cause of most engine longevity problems and therefore every pilot should buy their product. This document, if read and understood by all pilots (errors and all) would go a long way toward reducing the number of pilot induced premature engine overhauls.
With the exception of some errors, either out of ignorance or misinterpretation, or willful misrepresentation (I doubt this), I maintain that the document has some value. Of course, you are free to disagree vehemently with me.
As you noted, different engine manufacturers specify different % power over which LOP is not good for the engine. Jabiru apparently uses 70% power since the jet needle they designed for the Bing 94 begins getting much richer at approximately that power setting, assuming the prop used is within the rpm specs. they recommend.
--------
Thom Riddle
Buffalo, NY
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
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jetboy
Joined: 22 Jul 2006
Posts: 233
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| Posted: Fri Apr 23, 2010 3:22 pm Post subject: Re: Excellent treatise on LOP operation |
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The fact that Jabiru start leaning below around 70% power does not imply they approve of running the engine LOP at any time.
The econony jetting never operates in the LOP zone, even the first version which was savagely lean in some circumstances, did not operate on the lean side of peak EGT at any throttle setting. (Arguably it would have been better to have operated LOP than in the "just ROP" danger zone that the initial economy kit put it) Jabiru since revised the jetting about 4 times to get it safe, according to the JSB.
I'm just making the point here that LOP means lean of the peak EGT that occurs while manually leaning the mixture, at the current operating power setting. LOP operation can be confirmed by applying carb heat and observing an increase of EGT, rather than the usual decrease, that occurs when the mixture is at or rich of peak EGT.
its good to see the Aerocarb and Rotec injector carbs being used but won't take the risk or expense with mine as I've already replaced 4 exhaust valves at 310 hrs and feel a top overhaul is going to occur in a similar time. I would consider doing it on a new engine once the track record of those engines proven, but mine's half cut already and I want it reliable for the remainder, theres enough other issues to be concerned about.
Ralph
[As you noted, different engine manufacturers specify different % power over which LOP is not good for the engine. Jabiru apparently uses 70% power since the jet needle they designed for the Bing 94 begins getting much richer at approximately that power setting, assuming the prop used is within the rpm specs. they recommend.[/quote]
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