Lean of Peak

[Horis]

I have a TIO-540 in a Bravo.  I have seen a lot of data stating that LOP is better for your engine and saves fuel.  The scientific data looks good, but Lycoming is adamant that you should never fly LOP.  Let's hear your experience.

[A64Pilot]

I believe Lycoming is so adamant about it because of two reasons.

1. LOP is a reduction in power for the same MP and RPM, and marketing wise power sells.

2. Pretty hard to hurt a motor if you operate it IAW Lycoming’s instructions, but I believe Lycoming has seen and sees a lot of damage from detonation, likely coming from people running LOP too aggressively and or not being careful enough as in paying close enough attention or not understanding well enough what’s going on, so operating IAW Lycomings instructions is the most conservative and safest method, it’s very unlikely to detonate if you follow Lycomings instructions.

If I owned a large high power turbo motor, I’d operate it IAW Lycomings instructions assuming of course I bought the beast to go fast and not to save fuel, personally I operate almost exclusively LOP, but I bought a J model, largely for its efficiency, in other words to save fuel AKA keep costs down. That 540 is I’m told a not inexpensive motor to own.

Many will decry what I’m saying touting they do it all the time and haven’t hurt anything and that Lycoming are a bunch of fools, they don’t know anything, just happen to build the motor. But the potential of harm at high power LOP is real, where the potential for harm high power ROP is much less. Very little potential for damage LOP at low power, but why have that motor to operate it at low power.

If the motor is under Warranty I would not operate it any way except the Lycoming way.

Finally, call Lycomings help desk and ask them, over the years I’ve called with a couple of questions and they have been very frank and knowledgeable, and it’s a free call.

On edit, ask yourself why Lycoming would tell you to operate their motor inconsistent with it living a long and trouble free life? Engines known for long and trouble free operation sell well, ones that don’t have that rep, don’t.

Oh, if you decide to run LOP, I wouldn’t do so myself in a high workload environment like hard IFR while receiving reroutes or anything that has you task saturated, I’d go back to well ROP so you could take that concern off your task list, save it for those boring VFR flights

[carusoam]

3 hours ago, Horis said:

I have a TIO-540 in a Bravo.  I have seen a lot of data stating that LOP is better for your engine and saves fuel.  The scientific data looks good, but Lycoming is adamant that you should never fly LOP.  Let's hear your experience.

Horis,

You have a lot of good open ended questions…  great for conversation starters at a Mooney fly-in…! 

Are you seriously interested in a response, or you trying to gauge people’s interest in typing?

 

See if we can get you up to speed on the easy ones…

Start with putting your airplane model in your avatar area…. People use this info to adjust their answers…

 

Know that there is a Bravo section around here…. Where the answers for LOP specific to the Bravo can be found…

 

Know that The use of LOP with the Bravo comes with many mixed reviews…

The log style intake system isn’t balanced well enough to keep most pilots happy when operating LOP…  compare to the curvy intake pipes that do this better…

Stay focussed, keep reading… you are going to get pages of responses…

 

Use caution… when you ask a lot of questions that already have answers back to the turn of the century….   People stop doing your homework for you…   

 

The search function around here can be kind of crummy…   Often, people use Google to search MS from the outside….

 

Basic Questions about LOP vs. ROP or flaps vs. no flap T/Os….  Raise flags…

You might want to introduce yourself… mention your background… How long have you had this plane… what kind of Transition Training you have gone through…

Best regards,

-a-

 

[Fly Boomer]

2 hours ago, A64Pilot said:

I believe Lycoming has seen and sees a lot of damage from detonation, likely coming from people running LOP too aggressively and or not being careful enough as in paying close enough attention or not understanding well enough what’s going on, so operating IAW Lycomings instructions is the most conservative and safest method,

Do you mean it's likely coming from people who are operating too far LOP, and that is causing detonation?

[carusoam]

46 minutes ago, Fly Boomer said:

Do you mean it's likely coming from people who are operating too far LOP, and that is causing detonation?

Are we discussing red box theory?

The red box requires…

1) Power above 65%bhp

2) Mixture close-ish to peak 

 

Soooo… operating too far LOP takes the engine away from peak, and falls out of the red box…

 

PP thoughts only, not an engine guru…

Best regards,

-a-

[jaylw314]

IIRC, Lycoming has no specific limitations for the IO-360 in its operating handbook, and it has separate written guidance about leaning to whatever you want above 5000' MSL or below 75% power (I think those are both unofficially written, though).  Most of the Lycoming "insistence" on avoiding LOP comes from stories of interactions with individuals representing the company.

Not sure if this is the same situation with the TIO-540?

[GeeBee]

LOP requires good intake system, nicely matched injectors, strong ignition system. 

As mentioned the Lycoming intake system is not as finely tuned as the Continental cross flow system. You can get GAMI injectors if the factory units are not well matched and it can compensate for the intake.  Then you can work on the ignition system to make it strong, good mags, fine wire plugs.

To know where you are you need to run a GAMI profile test flight. Examine the data and see where you are.

Finally when leaning out you need to be careful not to linger in high TIT area too long as your turbo does not like it. Remember with the waste gate closed, mixture not only affects TIT it affects turbine speed which changes MP very quickly.  Personally, I would not operate a turbo Lycoming LOP above 65%. 

[Pinecone]

4 hours ago, Fly Boomer said:

Do you mean it's likely coming from people who are operating too far LOP, and that is causing detonation?

It is more people who half heartedly run LOP.  And don't run lean enough.

[Fly Boomer]

4 minutes ago, Pinecone said:

It is more people who half heartedly run LOP.  And don't run lean enough.

Ah.  That makes sense.

[EarthboundMisfit]

9 hours ago, Horis said:

I have a TIO-540 in a Bravo.  I have seen a lot of data stating that LOP is better for your engine and saves fuel.  The scientific data looks good, but Lycoming is adamant that you should never fly LOP.  Let's hear your experience.

Is that a recent written statement by Lycoming?  

Here’s the APS rebuttal to Lycoming on LOP ops from many moons ago - https://www.advancedpilot.com/articles.php?action=article&articleid=1838

[LANCECASPER]

On 10/11/2022 at 6:52 AM, Horis said:

I have a TIO-540 in a Bravo.  I have seen a lot of data stating that LOP is better for your engine and saves fuel.  The scientific data looks good, but Lycoming is adamant that you should never fly LOP.  Let's hear your experience.

You won't have much to worry about. There are probably one or two people on here that have been able to get that engine to run smoothly enough to run it lean of peak. I owned three Bravos and knew nothing about LOP on the first one 26 years ago, but never was able to get either of the last two to run smoothly enough to fly that way, even after GAMI injectors. There are a lot of things to like about Lycoming TIO-540 engines but the Continental TSIO-550 or IO-550 have a much better balanced intake which helps with LOP.

[A64Pilot]

9 hours ago, Fly Boomer said:

Do you mean it's likely coming from people who are operating too far LOP, and that is causing detonation?

No without reading all the responses you cannot operate too far LOP, you can however not operate far enough LOP.

I’m sorry I got bad news from the Dr today, I have MERSA in my right knee replacement and I’m not being real clear posting right now. 

If your real LOP detonation isn’t possible, but power sucks, maybe people get greedy and want LOP and power and don’t go lean enough and get into trouble.

The IO-540 just doesn’t seem to like LOP, where the NA IO 360 angle valve seems to relish in it. I think if I had a B I’d operate operate ROP, where my J seems happy LOP

[Shadrach]

As Lance says above, this engine is known to be a challenge to run on the lean side of peak.

I don't know what Lycoming's official stance is today, but they acknowledged years ago that LOP was a perfectly acceptable place to run an engine in the document “EXPERTS” ARE EVERYWHERE TO HELP YOU. It was printed in 2000 and was in my opinion, a cheap shot at George Braly, Gami, APS and anyone else that believed that there are scenarios where LOP operations are more practical, efficient and healthy for an engine.  I won't get into analyzing Lyc's document.  John Deakin (Pelican's Perch columnist and APS instructor) wrote a pretty thorough rebuttal.  Those were heady days in the ROP LOP debate...Good thing we've come so far in 22 years.  There is still a lot of misunderstanding in the pilot community about combustion science and therefore a lot of well intentioned misinformation. In the early 00’s, I was fortunate that Walt Atkinson (RIP) an APS instructor whom I became acquainted with online was kind to me, a then 20 something just starting to fly high performance singles. He answered a lot of my questions both in forums and via email. I will forever be grateful for his generosity.

There are two graphics below. One is a conceptual chart published by Lycoming. The other depicts the actual internal cylinder pressure (ICP) of a Continental six and was taken from an excellent article written by Mike Busch. It is worth the short read.

As you can see from both graphs peak CHT, peak pressure, lowest detonation margin etc... all occur about 50° rich of peak EGT.  In the past both manufacturers recommended cruise settings of 100° ROP.  There is no setting on the lean side that is as aggressive as that setting from an ICP standpoint.  "Running LOP too aggressively" is not a real thing.  Lean mixture ratios are more difficult to ignite than rich mixtures. They are also more resistant to detonation, not less so.   An engine will not detonate if all cylinders are on the lean side of peak EGT under any practical scenario.  So regardless of what Lyc says, their graph shows that all LOP settings are cooler than their recommended setting of 100° ROP. 

.

Below is a graph taken from the aforementioned Mike Busch article.  This is actual data as opposed to Lycoming’s theoretical/conceptual depiction. This is a more sophisticated analysis that shows actual cylinder pressure in relation to crank angle (which is crucial to extracting energy from the combustion event). CHT‘s are driven by cylinder pressure. Here we can see that every setting on the rich side of peak (including full rich) has lower detonation margins than Peak EGT, going leaner only increases margins. We can also see that from peak to 50° LOP the slower burning combustion event produces a more ideal pressure profile in relation to crank angle. The pressure drop is less steep producing similar mean cylinder pressure over the power stroke but with a lower peak and less severe pressure drop after peak. This is best BFSC range.  The engine is extracting the most mechanical energy from a unit of gas and generating less heat/peak pressure in the process.  Read the above linked Savvy article.  It's short and to the point and will clarify some of the well intentioned but less than factual guidence that you might find here and elsewhere.

 

[Fly Boomer]

@A64Pilot Sorry to hear about the knee.  Keep after the bast@&ds until they find a solution.

[A64Pilot]

You cannot compare one engine with another, my IO-540 W1A5D sucked LOP, my IO-360 loves it, you would think one is four cyl, the other 6 cyl, otherwise identical, but they are no where near the same.

 Different engines are different, you can’t compare them. If your engine runs LOP fine, rejoice and run it till your hearts content, if it doesn’t don’t gnash your teeth, it doesn’t drive on ROP and enjoy life.  it’s not really a big difference if you run the numbers, it’s a fraction of what flying costs.

Yeah, the knee sucks, you grow old, then you die, that sucks,

 But thanks for the well wishing, I appreciate it it. Because what else is there?

 

[Shadrach]

18 minutes ago, A64Pilot said:

No without reading all the responses you cannot operate too far LOP, you can however not operate far enough LOP.

I’m sorry I got bad news from the Dr today, I have MERSA in my right knee replacement and I’m not being real clear posting right now. 

If your real LOP detonation isn’t possible, but power sucks, maybe people get greedy and want LOP and power and don’t go lean enough and get into trouble.

The IO-540 just doesn’t seem to like LOP, where the NA IO 360 angle valve seems to relish in it. I think if I had a B I’d operate operate ROP, where my J seems happy LOP

Sorry about your knee situation. Hope the infection subsides soon. MERSA sucks.

[Fly Boomer]

10 hours ago, A64Pilot said:

Yeah, the knee sucks, you grow old, then you die, that sucks,

Many years ago, a little bitty Jewish woman (not sure why this is significant) said to me "Life's a bitch; then you die."  That was at least 50 years ago, and I still can't get it out of my head.

[A64Pilot]

13 minutes ago, Fly Boomer said:

Many years ago, a little bitty Jewish woman (not sure why this is significant) said to me "Life's a bitch; then you die."  That was at least 50 years ago, and I still can't get it out of my head.

Yeah it sucks, knee has to come out, then a spacer inserted soaked if you will with antibiotics, then about 8 weeks of an antibiotic drip and oral antibiotics, then if the infection is gone, reimplant another knee with antibiotics in the cement (cemented implants are inferior to one the bone grows into). If the infection isn’t gone then I lose the leg, above the knee. With all this surgery you lose quite a bit of range of motion if best case you get another knee.

From what I gather from Google I have an about 85% survival rate, I think if it goes septic, you lose more than the leg

[Fly Boomer]

2 minutes ago, A64Pilot said:

Yeah it sucks, knee has to come out, then a spacer inserted soaked if you will with antibiotics, then about 8 weeks of an antibiotic drip and oral antibiotics, then if the infection is gone, reimplant another knee with antibiotics in the cement (cemented implants are inferior to one the bone grows into). If the infection isn’t gone then I lose the leg, above the knee. With all this surgery you lose quite a bit of range of motion if best case you get another knee.

From what I gather from Google I have an about 85% survival rate, I think if it goes septic, you lose more than the leg

I've had plenty of things fail, but no experience with that one.  All I can suggest is find the strength to beat down whatever obstacle is in front of you each day -- there are times when trying to strategize a master plan for the big picture is just not possible.

[A64Pilot]

11 hours ago, Shadrach said:

As Lance says above, this engine is known to be a challenge to run on the lean side of peak.

I don't know what Lycoming's official stance is today, but they acknowledged years ago that LOP was a perfectly acceptable place to run an engine in the document “EXPERTS” ARE EVERYWHERE TO HELP YOU. It was printed in 2000 and was in my opinion, a cheap shot at George Braly, Gami, APS and anyone else that there are scenarios where LOP operations are more practical and healthy for an engine.  I won't get into analyzing Lyc's document.  John Deakin (Pelican's Perch columnist and APS instructor) wrote a pretty thorough rebuttal.  Those were heady days in the ROP LOP debate...Good thing we've come so far in 22 years.  There is still a lot of misunderstanding in the pilot community about combustion science and therefore a lot of well intentioned misinformation. I was fortunate in that Walt Atkinson (RIP) an APS instructor whom I became acquainted with online was kind to me, a then 20 something just starting to fly high performance singles. He answered a lot of my questions both in forums and via email and I will forever be grateful for his generosity.

There are two graphics below. One is a conceptual chart published by Lycoming. The other depicts the actual internal cylinder pressure (ICP) of a Continental six and was taken from an excellent article written by Mike Busch. It is worth the read.

As you can see from both graphs peak CHT, peak pressure, lowest detonation margin etc... all occur about 50° rich of peak EGT.  In the past both manufacturers recommended cruise settings of 100° ROP.  There is no setting on the lean side that is as aggressive as that setting from an ICP standpoint.  "Running LOP too aggressively" is not a real thing.  Lean mixture ratios are more difficult to ignite. They are also more resistant to detonation, not less so.   An engine will not detonate on the lean side of peak under any practical scenario.  So regardless of what Lyc says, their graph shows that all LOP settings are cooler than their recommended setting of 100° ROP. 

.

Below is a graph take from the aforementioned Mike Busch article.  This is actual data as opposed to a conceptual depiction. This is a more sophisticated analysis that shows actual cylinder pressure in relation to crank angle (which is crucial to extracting energy from the combustion event). Here we can see that every setting on the rich side of peak (including full rich) has lower detonation margins than Peak EGT, going leaner only increases margins. We can also see that from peak to 50° LOP the slower burning combustion event produces a more ideal pressure profile in relation to crank angle. The pressure drop is less steep producing similar mean cylinder pressures but with lower peaks. This is best BFSC range.  The engine is extracting the most mechanical energy from a unit of gas and generating less heat/peak pressure in the process.  Read the above linked Savvy article.  It's short and to the point and will clarify some of the well intentioned but less than factual guidence that you might find here and elsewhere.

 

The chart you posted leaves out something very important, CYL head temp, for instance the point LOP that gives the same HP as full rich, can’t be used because temps get out of control, if it could we would run LOP during takeoff and climb. We takeoff and climb full rich to control temps, if not for temps, full rich would be best power, or maybe that point that’s a tiny bit LOP that gives the same power

High temps will drive detonation, so that chart only shows part of the picture

[alextstone]

@A64Pilot, I am at a loss for how to express my empathy for your challenges with your knee.   As my dad used to say, "Never quit on the uphill!"

[JimB]

This is basically LOP, they just call it "best economy mixture". 

https://www.lycoming.com/content/leaning-lycoming-engines

"For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting. NOTE: When leaned, engine roughness is caused by misfiring due to a lean fuel/air mixture which will not support combustion. Roughness is eliminated by enriching slightly until the engine is smooth."

[Marauder]

Yeah it sucks, knee has to come out, then a spacer inserted soaked if you will with antibiotics, then about 8 weeks of an antibiotic drip and oral antibiotics, then if the infection is gone, reimplant another knee with antibiotics in the cement (cemented implants are inferior to one the bone grows into). If the infection isn’t gone then I lose the leg, above the knee. With all this surgery you lose quite a bit of range of motion if best case you get another knee.
From what I gather from Google I have an about 85% survival rate, I think if it goes septic, you lose more than the leg

Hang in there. My father-in-law dealt with an infection with his knew replacement and overcame it. His biggest aggravation with the situation was being kneeless for the time it takes to heal.


Sent from my iPad using Tapatalk Pro

[Pinecone]

13 hours ago, Shadrach said:

As Lance says above, this engine is known to be a challenge to run on the lean side of peak.

I don't know what Lycoming's official stance is today, but they acknowledged years ago that LOP was a perfectly acceptable place to run an engine in the document “EXPERTS” ARE EVERYWHERE TO HELP YOU. It was printed in 2000 and was in my opinion, a cheap shot at George Braly, Gami, APS and anyone else that believed there are scenarios where LOP operations are more practical, efficient and healthy for an engine.  I won't get into analyzing Lyc's document.  John Deakin (Pelican's Perch columnist and APS instructor) wrote a pretty thorough rebuttal.  Those were heady days in the ROP LOP debate...Good thing we've come so far in 22 years.  There is still a lot of misunderstanding in the pilot community about combustion science and therefore a lot of well intentioned misinformation. In the early 00’s, I was fortunate that Walt Atkinson (RIP) an APS instructor whom I became acquainted with online was kind to me, a then 20 something just starting to fly high performance singles. He answered a lot of my questions both in forums and via email and I will forever be grateful for his generosity.

There are two graphics below. One is a conceptual chart published by Lycoming. The other depicts the actual internal cylinder pressure (ICP) of a Continental six and was taken from an excellent article written by Mike Busch. It is worth the read.

As you can see from both graphs peak CHT, peak pressure, lowest detonation margin etc... all occur about 50° rich of peak EGT.  In the past both manufacturers recommended cruise settings of 100° ROP.  There is no setting on the lean side that is as aggressive as that setting from an ICP standpoint.  "Running LOP too aggressively" is not a real thing.  Lean mixture ratios are more difficult to ignite than rich mixtures. They are also more resistant to detonation, not less so.   An engine will not detonate if all cylinders are on the lean side of peak EGT under any practical scenario.  So regardless of what Lyc says, their graph shows that all LOP settings are cooler than their recommended setting of 100° ROP. 

.

 

 

Funny thing is, Lycoming says to not run LOP, but that chart shows that the Best Economy Cruise in the lean of peak range.

[A64Pilot]

40 minutes ago, JimB said:

This is basically LOP, they just call it "best economy mixture". 

https://www.lycoming.com/content/leaning-lycoming-engines

"For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting. NOTE: When leaned, engine roughness is caused by misfiring due to a lean fuel/air mixture which will not support combustion. Roughness is eliminated by enriching slightly until the engine is smooth."

That’s for carbureted motors and may be LOP, but likely not, most carb motors just won’t do LOP, they get rough first. It’s the way most were taught to lean forever, that is once at cruise very slowly lean until rough, then slow enrichen until just smooth, in other words run as lean as it will run, most likely that puts you close to peak egt

Higher power cruise but still less than 75%, I was taught to lean until peak egt, then enrichen two hash marks cooler than peak, which I believe is 50 ROP

You can do a few things to help, like don’t quite be full throttle, idea is with the throttle partially closed it creates turbulence that may help with mixture distribution, and a little carb heat may help atomize the fuel, and you may be able to go LOP but probably not.

LOP isn’t really possible for a very large portion of the fleet, and you know those motors do fine.