ROP

[GaryP1007]

So much talk about LOP I would love to hear from those who are proponents of ROP. Pre-Mooney I always flew ROP. I was trained in the Mooney to use LOP.  

[A64Pilot]

You can’t hurt a motor if flown properly ROP, by proper I mean enough ROP.

You’ll make the most power ROP.

However the BSFC is best slightly LOP, which of course means lowest consumption per HP, but if your really in a hurry ROP is fastest and you’ll burn fuel to go fast too of course.

Personally I’ll take off and climb ROP and transition to LOP and a power setting of less than 65% which has me usually cruising in the 130’s and not the 150’s to save fuel and I’m rarely in a hurry.

LOP and I don’t have to clean plugs.

If your not careful you can hurt a motor LOP by trying to go fast (high power) LOP, so my operations are LOP for out flying for fun and ROP for making high power.

LOP is not new, my Father flew his C-210 in the early 70’s LOP and many if not most did, just it wasn’t called LOP and there wasn’t an internet etc., they just called it leaning it out. It wasn’t considered to be a big deal, it was just slowing down and saving fuel.

LOP and ROP both have their places and I maintain you can operate LOP safely in a stock IO-360 with stock instrumentation, just accept you need to be less than 75% power to do so. If I start out at a chart power setting of 75% power by the time I go LOP, power is way less than 75% of course. I generally operate deeper LOP than the best BSFC point for an added cushion. Personally I’m down to less than 65% flying C-182 speeds. I’m after efficiency more than speed, your mission may be different.

But my opinion is that both are fine, I don’t discriminate based on a persons religious beliefs  

Edited May 15, 2022 by A64Pilot

[Shadrach]

29 minutes ago, GaryP1007 said:

So much talk about LOP I would love to hear from those who are proponents of ROP. Pre-Mooney I always flew ROP. I was trained in the Mooney to use LOP.  

At DA’s above 8,000ft I am always ROP. I only run LOP when I have enough MP available to make good power. This means LOP down low closer to peak in the 5-10K range transitioning to ROP as I get higher. 12,000 and above I run 100ROP unless the winds are really favorable at which point I’ll set peak and enjoy the MPG.

[M20F]

Fuel is the least of my expenses, ROP or bust. 

[PT20J]

A really simple way to look at it is that the engine is an air pump and it can only pump so much air. In a perfect world, you would mix exactly the right amount of fuel to combine with all the oxygen molecules in the air. But combustion is a complicated process and takes finite time. In a furnace you can get closer to ideal combustion, but in an internal combustion engine the piston is moving and the temperature and pressure change during the combustion event and it is hard to get perfect combustion. To get the most power, extra fuel can be added in excess of the amount theoretically required which pretty much guarantees that almost all of the oxygen gets consumed. But not all the fuel will be consumed and so some is wasted and the efficiency decreases. Also, you get a lot of incomplete combustion products in the exhaust which increases combustion chamber deposits and air pollution. Running leaner than a theoretically perfect mixture (called stoichiometric, also peak EGT) pretty much guarantees that all the fuel will be consumed, so the efficiency goes up. But there is left over air so the power output drops. Because the combustion of the hydrocarbons is more complete, the deposits and pollution are reduced.

[toto]

2 hours ago, GaryP1007 said:

So much talk about LOP I would love to hear from those who are proponents of ROP. Pre-Mooney I always flew ROP. I was trained in the Mooney to use LOP.  

I always fly ROP per the "Best Power" performance charts in the flight manual.  At WOT/2500 in my J, leaning ROP typically tracks the book fuel flow numbers.

The ROP endurance of the airplane (6 hours ish) is still beyond normal bladder endurance, and I can't think of any reason I would want to go slower

[jaylw314]

I just fly at 9 GPH once I'm over 5000' MSL.  I'm LOP lower, ROP higher, fast enough that I don't care which and CHT's are cool enough it doesn't matter.

[Schllc]

6 hours ago, A64Pilot said:

 

If your not careful you can hurt a motor LOP by trying to go fast (high power) LOP, so my operations are LOP for out flying for fun and ROP for making high power.

 

What physically occurs in an engine that is damaged by less fuel than oxygen in the combustion cycle?

lower power obviously, but the product of this is lower egt’s and cht’s. 
how can this damage the engine? Can you explain how an engine can be damaged by lop?
 

I have only owned continental io550’s and tsio550’s and I have never had to replace a cylinder, do valve or piston work or any major engine work and I fly almost exclusively lop. I also know most of the people that bought my previous planes and they all fly lop and haven’t had issues either. 
I know this is a small sample so the question isn’t intended to be combative, it’s serious. 

[201er]

7 hours ago, GaryP1007 said:

So much talk about LOP I would love to hear from those who are proponents of ROP. 

I fly ROP every flight. Can’t have too much power to takeoff and climb in a 201.

But at the cost of soaring gas prices, it’s just nutty to spend an extra couple gallons simply as coolant in cruise.

Edited May 16, 2022 by 201er

[KLRDMD]

On 5/15/2022 at 1:41 PM, GaryP1007 said:

So much talk about LOP I would love to hear from those who are proponents of ROP. Pre-Mooney I always flew ROP. I was trained in the Mooney to use LOP.  

Someone trained you well 

[ArtVandelay]

Climb at ROP of course, otherwise LOP…Our engines are big enough polluters without dumping leaded fuel out the tailpipe.
It costs me about 15 minutes more on a 500nm trip to run LOP. Not a big issue as I like to fly.

[A64Pilot]

On 5/15/2022 at 11:15 PM, Schllc said:

What physically occurs in an engine that is damaged by less fuel than oxygen in the combustion cycle?

lower power obviously, but the product of this is lower egt’s and cht’s. 
how can this damage the engine? Can you explain how an engine can be damaged by lop?
 

I have only owned continental io550’s and tsio550’s and I have never had to replace a cylinder, do valve or piston work or any major engine work and I fly almost exclusively lop. I also know most of the people that bought my previous planes and they all fly lop and haven’t had issues either. 
I know this is a small sample so the question isn’t intended to be combative, it’s serious. 

I said if your not careful, for instance you could be busy and be told to change altitude, this could put you in what people call the red box and that can damage the engine, less likely to happen if your ROP because ROP operations are further from peak so more cushion. 25 LOP puts you pretty close to that box where 100 ROP is further away.

If you run lower power LOP, there simply is no box, you can’t hurt the motor, besides usually the point of LOP is to save fuel, slowing down is at least as effective to save fuel, and you save even more at higher altitude, so LOP at 65% or less you can’t hurt anything, flying at an altitude where 65% or less is all you can make saves fuel, all NA motor of course. 75% is actually the number I think for a Lycoming, but I use 65% for a greater margin

So simply put if you fly where there is no red box, you can’t hurt anything. If you try to fly fast LOP then there is a red box and you can hurt the engine

Edited May 17, 2022 by A64Pilot

[GaryP1007]

15 hours ago, KLRDMD said:

Someone trained you well 

Agreed!

[Schllc]

10 hours ago, A64Pilot said:

I said if your not careful, for instance you could be busy and be told to change altitude, this could put you in what people call the red box and that can damage the engine, less likely to happen if your ROP because ROP operations are further from peak so more cushion. 25 LOP puts you pretty close to that box where 100 ROP is further away.

If you run lower power LOP, there simply is no box, you can’t hurt the motor, besides usually the point of LOP is to save fuel, slowing down is at least as effective to save fuel, and you save even more at higher altitude, so LOP at 65% or less you can’t hurt anything, flying at an altitude where 65% or less is all you can make saves fuel, all NA motor of course. 75% is actually the number I think for a Lycoming, but I use 65% for a greater margin

So simply put if you fly where there is no red box, you can’t hurt anything. If you try to fly fast LOP then there is a red box and you can hurt the engine

What physically occurs in these zones that causes damage is what I meant. 
For example, excessive rop operations can fry a turbo if you aren’t careful, it also fouls plugs and exhaust valves. 
What kinds of things happen in lop?  
I am really curious about this, you guys have so many more years of experience with these engines and aviation than I do, and I am very eager to benefit from that experience.

I have always approached the lop vs rop argument from a simple physics perspective.  Engine care is about heat management, period. 
I think genesis of the conventional wisdom/proponents about/of  rop was a combination of ignorance (not stupidity), and inability to really monitor what your engine was doing. 
An analog gauges that shows the temperature of the hottest probe doesn’t tell you if three probes have failed….
Most people that own planes are people of means, not wealth perhaps but means…But being wealthy doesn’t make you smart, or conscientious.

I have flown with people in brand new planes that had complete unawareness of what they were doing to their engine.  One idled at 1600rpm all the way from startup to the hold short and when I asked him why, he said “this engine loves fuel”.. uhhhhh  ok

My point is, I haven’t really found anything that tells me how running lop can damage an engine, and I really don’t understand the debate.  I realize it can be done safely, but at least in my plane gaining 5-8 knots for an additional 4 gallons per hour, only to have the belly white from burnt fuel in the exhaust, fouled plugs, and 30-50deg hotter cylinder head temps isn’t worth it. 
Reliability and longevity are the only thing I care about with regard to engine management.  
I would like to know what I’m risking lop, out of the box, in the box…  

What happens out of the box?  Please don’t take this as an argument, it’s a sincere question.  I don’t understand, other than fuel exhaustion, how you can hurt the engine.

I don’t care if I convince anyone of anything,  just want to take care of my plane the best way I can  

 

[tgardnerh]

What physically occurs in these zones that causes damage is what I meant. 
For example, excessive rop operations can fry a turbo if you aren’t careful, it also fouls plugs and exhaust valves. 
What kinds of things happen in lop?  
I am really curious about this, you guys have so many more years of experience with these engines and aviation than I do, and I am very eager to benefit from that experience.

I have always approached the lop vs rop argument from a simple physics perspective.  Engine care is about heat management, period. 
I think genesis of the conventional wisdom/proponents about/of  rop was a combination of ignorance (not stupidity), and inability to really monitor what your engine was doing. 
An analog gauges that shows the temperature of the hottest probe doesn’t tell you if three probes have failed….
Most people that own planes are people of means, not wealth perhaps but means…But being wealthy doesn’t make you smart, or conscientious.
I have flown with people in brand new planes that had complete unawareness of what they were doing to their engine.  One idled at 1600rpm all the way from startup to the hold short and when I asked him why, he said “this engine loves fuel”.. uhhhhh  ok
My point is, I haven’t really found anything that tells me how running lop can damage an engine, and I really don’t understand the debate.  I realize it can be done safely, but at least in my plane gaining 5-8 knots for an additional 4 gallons per hour, only to have the belly white from burnt fuel in the exhaust, fouled plugs, and 30-50deg hotter cylinder head temps isn’t worth it. 
Reliability and longevity are the only thing I care about with regard to engine management.  
I would like to know what I’m risking lop, out of the box, in the box…  
What happens out of the box?  Please don’t take this as an argument, it’s a sincere question.  I don’t understand, other than fuel exhaustion, how you can hurt the engine.
I don’t care if I convince anyone of anything,  just want to take care of my plane the best way I can  
 

Let me offer my paraphrase of Mike Busch and John Deakin (synthesizing the their separate writings and doubtless introducing my own errors). This will also be a good exercise for me as more knowledgeable folks correct me :-)

For a given HP, the closer the mixture is to stoichiometric (all O2 and fuel consumed, none of either left over) the higher the peak internal cylinder pressure, and the hotter the cylinder metal. Roughly speaking egt peaks when the mixture is stoichiometric.

GA engines can handle the pressures produced at peak egt at ~65% power or less.
The "red box" is roughly the set of power/leanness combinations that generate heat and pressure beyond what the engine is able to handle--which can lead to chronic cylinder damage from too much heat (eg the claim that leaning burns valves), or pre ignition and detonation (which can rapidly convert your airplane into a glider).

In cruise flight, if the cylinders are all roughly getting the same mixture, a safe way to operate LOP is to pull the red knob back until power drops, and then push it back in gradually until your hottest cylinder is as hot as you're willing to let it get. (This especially is my paraphrase--don't do this without independently convincing yourself that its prudent!)

Note also that when an engine is run "too lean" with catastrophic effects, usually whats happening is that its ROP at takeoff power, but because of a mechanical issue one or more cylinders are not rich enough.

I now await corrections!
--T


Sent from my iPhone using Tapatalk

[Schllc]

32 minutes ago, tgardnerh said:

Let me offer my paraphrase of Mike Busch and John Deakin (synthesizing the their separate writings and doubtless introducing my own errors). This will also be a good exercise for me as more knowledgeable folks correct me :-)

For a given HP, the closer the mixture is to stoichiometric (all O2 and fuel consumed, none of either left over) the higher the peak internal cylinder pressure, and the hotter the cylinder metal. Roughly speaking egt peaks when the mixture is stoichiometric.

GA engines can handle the pressures produced at peak egt at ~65% power or less.
The "red box" is roughly the set of power/leanness combinations that generate heat and pressure beyond what the engine is able to handle--which can lead to chronic cylinder damage from too much heat (eg the claim that leaning burns valves), or pre ignition and detonation (which can rapidly convert your airplane into a glider).

In cruise flight, if the cylinders are all roughly getting the same mixture, a safe way to operate LOP is to pull the red knob back until power drops, and then push it back in gradually until your hottest cylinder is as hot as you're willing to let it get. (This especially is my paraphrase--don't do this without independently convincing yourself that its prudent!)

Note also that when an engine is run "too lean" with catastrophic effects, usually whats happening is that its ROP at takeoff power, but because of a mechanical issue one or more cylinders are not rich enough.

I now await corrections!
--T


Sent from my iPhone using Tapatalk

Yes, this describes the reason one avoids “peak”.  Hence lean of peak and rich of peak. 
There are a number of documented deleterious effects of running at peak, there are also numerous quantifiable issues with running improperly  rop.  
I cannot find what those affect are from lop.
Everyone just says it can be bad, it can damage an engine, etc etc.  What are they?  
What damage occurs? What are the specific things that happen?

I mean if over leaning an engine damages an engine why do we pull the mixture to kill the engine?  I know this is over simplifying to an extent, but every time I ask, the answer is just that you aren’t supposed to…

I mean once again it’s just about heat management and lop’s biggest side effect is less heat….

[PT20J]

Well, sort of. Stoichiometric mixtures burn the fastest and hottest, but they don't produce the highest pressures, temperatures or most power in an internal combustion engine for a number of chemical, thermodynamic and mechanical reasons. 

Lycoming generally allows any mixture when 75% or less rated power. Continental uses 65% or less. Continental valves are solid and Lycoming's are sodium filled which allows them to run hotter.

The limiting factor in all heat engines is, well, heat. The SR-71 generally cruised at Mach 3.1. It had enough power to go faster, but the limiting factor was the engine inlet air temp. Internal combustion engines are the same. The CHT gauge is not at the hottest part of the cylinder head. The exhaust valves and spark plugs run hotter. If you keep the temps under control, the engine lives longer. The temperature is determined by power and mixture, and the pilot has control over both.

Skip

 

[Schllc]

17 minutes ago, PT20J said:

Well, sort of. Stoichiometric mixtures burn the fastest and hottest, but they don't produce the highest pressures, temperatures or most power in an internal combustion engine for a number of chemical, thermodynamic and mechanical reasons. 

Lycoming generally allows any mixture when 75% or less rated power. Continental uses 65% or less. Continental valves are solid and Lycoming's are sodium filled which allows them to run hotter.

The limiting factor in all heat engines is, well, heat. The SR-71 generally cruised at Mach 3.1. It had enough power to go faster, but the limiting factor was the engine inlet air temp. Internal combustion engines are the same. The CHT gauge is not at the hottest part of the cylinder head. The exhaust valves and spark plugs run hotter. If you keep the temps under control, the engine lives longer. The temperature is determined by power and mixture, and the pilot has control over both.

Skip

 

Heat management……

[carusoam]

LOP is over rated!!!
 

Damn the air to air missiles captain!
Full speed ahead!!!

When it comes to OPM….

Not only should you fly ROP…. But do so in full flaming dragon mode!  (FFDM)

 

Sure, there is the cost of a few cylinders at the half way point, when you are careful….

But, you have selected to fly fastly….

Who needs…

• Cleaner oil…
• better cylinder longevity…
• nicely balanced FIs… (best for LOP, not so much ROP)

When you have the budget and the 100LL…

Go Mooney!

-1 for re-opening the ROP vs. LOP debate without referencing an older thread….

Best regards,

-a-

[Alan Maurer]

I read all the replies regarding LOP vs ROP. Using my Ovation I have tried both. So 100 F ROP vs 50 F LOP. Using ROP I burn five more gallons

cruising at 8000 feet. And I gain about 12 knots. Running 50 degrees LOP , I save 5 gallons per hour but 12 knots slower. Both seem OK.

IN a real hurry use ROP and go faster. Or LOP and save fuel. Flying around peak and CHT much higher and not good.....that red box!

Avgas is expensive but a Mooney is supposed to go fast.

Cheers

Alan

 

[ArtVandelay]

I read all the replies regarding LOP vs ROP. Using my Ovation I have tried both. So 100 F ROP vs 50 F LOP. Using ROP I burn five more gallons
cruising at 8000 feet. And I gain about 12 knots. Running 50 degrees LOP , I save 5 gallons per hour but 12 knots slower. Both seem OK.
IN a real hurry use ROP and go faster. Or LOP and save fuel. Flying around peak and CHT much higher and not good.....that red box!
Avgas is expensive but a Mooney is supposed to go fast.
Cheers
Alan
 

50° LOP ? I see no reason to go past 10° (richest cylinder), at that point you burning all the fuel so you have maximize the efficiency of combustion , anything more is just like pulling back on power.

[Pinecone]

One thing is, stoichiometric is not burning everything due to uneven mixing and uneven combustion.  Your engine can only take in so much air.  A little extra fuel ensures you are using all the oxygen, and that little bit extra fuel does not significantly change the amount of oxygen to use in combustion.

Best way to get knowledgeable about LOP operations is to take an APS Seminar.  They are available online now, in person hopefully soon.

[A64Pilot]

8 hours ago, Alan Maurer said:

I read all the replies regarding LOP vs ROP. Using my Ovation I have tried both. So 100 F ROP vs 50 F LOP. Using ROP I burn five more gallons

cruising at 8000 feet. And I gain about 12 knots. Running 50 degrees LOP , I save 5 gallons per hour but 12 knots slower. Both seem OK.

IN a real hurry use ROP and go faster. Or LOP and save fuel. Flying around peak and CHT much higher and not good.....that red box!

Avgas is expensive but a Mooney is supposed to go fast.

Cheers

Alan

 

Now to see the real fuel savings, pull the power back while ROP to the same AS you run while LOP. A lot of that 5 GPH goes away.

I have nothing against LOP, I run LOP myself, just like anything some over estimate it. They will do exactly what your saying, run ROP and burn X amount of fuel, then switch to LOP and burn X - some amount and proclaim Wow look at all the fuel you save, while a lot of it is actually from just slowing down. To quantify fuel savings you need to do so at equal HP, since we don’t have torque meters, we should do so at equal Airspeeds to compare apples to apples.

Your -50 is a little leaner than optimum, but if your at a power setting where the red box exists, then it’s conservative and in my opinion has a greater margin of safety. Years ago I ran -25 LOP in my Maule and Lycomings recommended 50 ROP, the difference in actual fuel consumption disappointed me, I’ve long since lost the numbers, but a 360 isn’t a 540 and a Maule isn’t a Mooney so maybe there is more fuel savings in a Mooney. To begin with my 360 is LOP’s poster child, it will stay smooth deep LOP, my 540 wasn’t, and I had Gami injectors and fine wire plugs, my 360 has neither. My 540 would get rough leaner than -25. It was a parallel valve motor.

On a different note, I’d love to know why Continental doesn’t use sodium filled exh valves, they have been around forever, the Wright Whirlwind that took Lindy over the N Atlantic had sodium filled exh valves. There must be a logical reason. I believe they are weaker, but we don’t have a problem with valve breakage.

 

Edited May 18, 2022 by A64Pilot

[Fly Boomer]

13 hours ago, Schllc said:

I would like to know what I’m risking lop

I only know what I read.  In recent years, the GAMI/APS guys and Mike Busch are in agreement.  Unless there is something wrong with your engine like a Heli-Coil tang extending into the combustion area:  NO RISK.  That said, you have to be absolutely certain you are LoP on all cylinders.  Some of the leaning techniques I read around here concern me.  I'm not interested in 10 dF lean of peak because there is too much risk that the hottest cylinder is not really lean of peak.  The only sort-of LoP risk I can think of is getting so lean that your cylinder temperatures are too low for adequate scavenging. Busch advocates for 380 max sustained CHT based on known metallurgic properties for Continental engines -- Lycoming can go a little higher.

[A64Pilot]

5 hours ago, Fly Boomer said:

I only know what I read.  In recent years, the GAMI/APS guys and Mike Busch are in agreement.  Unless there is something wrong with your engine like a Heli-Coil tang extending into the combustion area:  NO RISK.  That said, you have to be absolutely certain you are LoP on all cylinders.  Some of the leaning techniques I read around here concern me.  I'm not interested in 10 dF lean of peak because there is too much risk that the hottest cylinder is not really lean of peak.  The only sort-of LoP risk I can think of is getting so lean that your cylinder temperatures are too low for adequate scavenging. Busch advocates for 380 max sustained CHT based on known metallurgic properties for Continental engines -- Lycoming can go a little higher.

That is why I restrict LOP to 65% or less. I do not have an engine monitor and likely won’t, but I do know that if I restrict LOP to 65% or less I can’t possibly hurt anything no matter what I do with the mixture setting. Lycoming says 75% and I’m sure they are right, but 65% and I’m way safe. I like big margins

Everything is a risk / reward.  To me the possible reward of saving one or two GPH doesn’t outweigh the possible risk, but at 65% there is NO risk. Higher power I’ll go ROP where there is no risk either and just burn the extra fuel.