Is there any problem in running ROP as long as the temps are good?

[Steve Parker]

Recently bought a 2006 M20R Ovation with the 310 hp upgrade.  Just under 800 hours TT engine and airframe.  I've been spending all my time and energy trying to figure out my STEC 55X autopilot but avionics guys in Peoria confirmed its GPSS feature is broken.  I'm flying my wife to the Chicago area tomorrow morning and back Saturday.  When I flew to Peoria yesterday at 6,500' I leaned it out to smooth the operation and bring the temps to what seemed the best setting on the G1000 (EGT white arc on one side, CHT mid-green).  Is this okay for the engine?  At this point, having spent all my time regaining instrument proficiency after 30 years out of the cockpit I don't care for this trip if I burn more gas, I just want to do the right thing for long, safe engine life.

Is ROP with EGT white arc on one side, CHT mid-green, smooth engine operation good for the engine or do I need to run LOP for long engine life?  If so I'll start watching LOP videos.  As I said, I could care less if I burn a few gallons more on this trip but I don't want to build up carbon or otherwise harm the engine.

Thanks in advance for your advice.  

Edited October 7, 2022 by Steve Parker

[Pete M]

If you're running at 65% power or less it won't matter. Leaner is cleaner. It may take some fiddling to get smooth lop operation, gamijectors ect. For right now run reduced power for cruise and learn the airplane. Do a bunch of instrument work. Instead of running the engine hard to go fast look for the tas gain from altitude. 10 to 12k should work great. Above the cloud bases is always smoother. Cht's 325, 350 in cruise are fine. Its usually the climb where things get hot. I dont like my cht's much over 400 anytime if i can help it. I dont know what green range is on your plane but top of green is usually too hot for my liking. 

Edited October 6, 2022 by Pete M

[GeeBee]

You won't "harm" the engine by running ROP but it does get expensive in terms in fuel consumption and increased maintenance. I run 50 LOP at 65% on my O with 12.3 GPH. I use GAMI injectors. I have run hard at 75% 50 to 100 ROP to break in cylinders. What I notice is how much cleaner my oil analysis comes back LOP and when I do my borescope at oil change there is a marked change in the cleanliness of the cylinders and valves. In short, less fuel means a cleaner engine. A cleaner engine means less maintenance in particular with cylinders and valves not to mention sludge development which is a problem with the IO-550 because it is a small sump engine. Finally you will find your cylinders run cooler LOP, much cooler and that will give you longer cylinder life. For me, 325 is high temp at 65%, most the time I run 300 to sub 300 numbers. In the winter I have to keep an eye because a #1 & 2 can start to tickle the lower limit of 250 running LOP. So if you can get the speed you need, why not run it in the cleanest and coolest way possible?

I agree with your priorities. Get yourself comfortable with flying the airplane, and once that occurs you can start looking at precision engine management 

[Fly Boomer]

9 hours ago, GeeBee said:

I agree with your priorities. Get yourself comfortable with flying the airplane, and once that occurs you can start looking at precision engine management 

Especially while flying your wife to Chicago.  Not a good time to experiment with new engine management techniques.  If you employ the BMP technique (Big Mixture Pull), and the fire goes out, it could increase the pucker factor.  If I was doing it, I would be at 10,000 over my home airport on a perfectly clear, windless, mid-week day (very little traffic).  But that's me.

[Will.iam]

As long as you smoothly bring the mixture back i. E. Don’t yank it to cutoff, the engine will start running rough when you get too lean. Stop and enrich the mixture just enough to smooth out the roughness and that is the leanest you can go. Depending on how balanced your fuel injectors are this could be not LOP on 1 or more cylinders thus why they say if running at 65% power even if one of the cylinders is at peak or worst place to be 50 ROP you will not harm the engine. 

[Pinecone]

Agree, new to the airplane, don't worry about a few trips ROP.  People ran ROP for MANY years.

I did the same bring my plane home from TX.  I ran ROP, to reduce the new things by at least one factor.

 

[Shadrach]

1 hour ago, Fly Boomer said:

Especially while flying your wife to Chicago.  Not a good time to experiment with new engine management techniques.  If you employ the BMP technique (Big Mixture Pull), and the fire goes out, it could increase the pucker factor.  If I was doing it, I would be at 10,000 over my home airport on a perfectly clear, windless, mid-week day (very little traffic).  But that's me.

One of the challenges for me when I first started flying LOP was minimizing the “feel” of over shooting on the lean side to rough. No passenger wants to hear an engine stumble even if you prepare them for it.

[Mufflerbearing]

Running LOP or ROP is always a great read.  I love all of the comments and people's experiences.  One thing that is oftentimes overlooked is not just fuel mixture, but the sparkey bolts.  My plane really struggled with taxiing and LOP operations were just ok.  I took out the Champion massives and checked them out for resistance.  10 failed out of 12 and 3 were open resistance.  Not sure how this plane ever ran with these horrible plugs.  I then changed out to Tempest fine wire plugs on top and bottom and just that fast, no more issues with taxiing, hot starts are a cinch and LOP is 11.5 GPH at 167 TAS at 11,000' (having FIKI is a speed penalty)  Clean oil at changes and cooler temps.  What exactly is the downside?  Next up is the installation of electronic ignition.

[A64Pilot]

An argument could be made these things were built to run ROP as that’s what the book settings were for decades. LOP however is not a newly discovered thing, many have been since WWII at least. While not a big sample size from what I have seen with big block Conti’s the ones run ROP seem to have fewer cylinder problems. Within reason you can’t hurt an engine ROP, but you can LOP by not being lean enough at high power. A dummy or a person with a lot going on can run ROP safely, LOP requires a little more attention to detail. Just remember you can’t be too LOP, the danger is in not being LOP enough so if there is any doubt, lean it out if LOP, just like if there is any doubt ROP, enrichen it.

My advice is to run ROP until you have everything down pat, it’s all automatic and your bored, then try the LOP thing, but save it for when your not in a hurry, if your in a hurry stick with ROP. Don’t be learning it IMC or in a busy ATC area

Biggest things I’ve seen for long engine life is frequent oil changes and low power as in 65% or less cruise. LOP or ROP

Ref fine wire plugs, they made more difference in running smooth LOP on my 540 and 520 than Gami injectors did, my 540 just wouldn’t run LOP worth a darn, the 520 did, but as I wasn’t buying gas for it, I ran it everywhere at 2500 and WOT if less than 25” and 100 ROP for 1500 hours without a hiccup, when I left it was still running strong with original cylinders. Above 25” put it in it’s 5 min limit, it was a 300 HP IO-520, for 5 min, 285 continuous.

Oh, for the record I fly my J model almost exclusively LOP, I am not against LOP. It has its place, as I’m Retired now and not in a hurry, LOP fits my flying.

[PT20J]

How far we’ve come. Years ago, people used to worry about risks of operating in ways contrary to the manufacturer’s recommendations. Now, there seems to concern about the risks of following them. 

[GeeBee]

I used to run 6 Cessna 402s as freighters. Some as much as 7 hours a day. Ran them all LOP. We concentrated on tight cooling, good fuel injection, good ignition. 98% of my cylinders made it to TBO, and these were Pacific Continental remans. 100% of my turbos made it to TBO. Now these engines were not cross flows like the IO-550 which is designed to run LOP. They were TSIO-520s. There is no reason not to run these engines LOP. 

[Fly Boomer]

Hard to know what individual pilots do, but I’m curious if any or all were flown WOT, like the 520s on Mike Busch’s 310?  Mike says he runs WOT on takeoff, en route, and all the way through descent until in the airport or approach environment.

[Shadrach]

1 hour ago, Fly Boomer said:

Hard to know what individual pilots do, but I’m curious if any or all were flown WOT, like the 520s on Mike Busch’s 310?  Mike says he runs WOT on takeoff, en route, and all the way through descent until in the airport or approach environment.

That’s how I run mine. Power is typically controlled with mixture and prop. I may throttle back in descent if it’s bumpy but otherwise my first reduction is made based on where I am going to drop the gear.

[Fly Boomer]

That’s it!

[kortopates]

Hard to know what individual pilots do, but I’m curious if any or all were flown WOT, like the 520s on Mike Busch’s 310?  Mike says he runs WOT on takeoff, en route, and all the way through descent until in the airport or approach environment.

Mike’s redline MAP is only 32”. That makes it much easier to stay at redline than most other Turbo’s; especially the highly boosted TSIO-360’s!
But very easy to do on any NA engine.


Sent from my iPhone using Tapatalk

[Mufflerbearing]

6 hours ago, Shadrach said:

That’s how I run mine. Power is typically controlled with mixture and prop. I may throttle back in descent if it’s bumpy but otherwise my first reduction is made based on where I am going to drop the gear.

This!!  I run WOT all of the time.  I believe this is a more efficient way to run the engine.  As a note, I don't go LOP until I am up and in cruise which is usually between 10-12k and MAP is 21" and at this point, with the MAP so low, can't hurt the engine at any mixture level.

[A64Pilot]

17 hours ago, Fly Boomer said:

Hard to know what individual pilots do, but I’m curious if any or all were flown WOT, like the 520s on Mike Busch’s 310?  Mike says he runs WOT on takeoff, en route, and all the way through descent until in the airport or approach environment.

Way I used to fly the 210, remember your climbing, so before I hit the 5 min time limit on 300 HP I was at 5,000 ft or so and below the 285 HP limit, keep climbing and fly at say 7,000 or above and your wide open, but down on power. I would fly WOT always, but not 2700, I’d pull it back to 2500. I’d usually cruise about 10K or so.

Doing this even at best power ROP your below 75% power, if your LOP it’s likely your below 65%. I wasn’t buying gas so I ran at best power because it was fastest.

Its the little Ag planes like the Cessna Ag wagon that pull the guts out of the big bore Continental’s as they are of course just a few hundred feet above sea level when ferrying and running hard because they are heavy, most I talked to would limit power to 25 squared or the engines wouldn’t last, and of course they don’t touch the mixture.

All other small Ag planes I’m aware of run Lycomings, even a few 720’s are left, but not many

[Fly Boomer]

1 minute ago, A64Pilot said:

If you ask Mike I’d bet lunch he’s flying at or below 21” or so MP and RPM pulled back a lot of the time even if WOT.

Mike’s engines are TSIO-520s so he is running 30-something inches (depends on the sub-model).  As you say, he does pull the prop back.  His technique is to watch fuel remaining vs time to waypoint or destination, and run fuel flow up or down (still LOP) to avoid a fuel stop.  If he can’t pull it back far enough to make it with reserves, he increases power to go faster en route to the fuel stop.  Also tries to get fuel at the highest airport elevation he can find.  Wastes less time getting back to cruise altitude.

[Shadrach]

11 hours ago, Mufflerbearing said:

This!!  I run WOT all of the time.  I believe this is a more efficient way to run the engine.  As a note, I don't go LOP until I am up and in cruise which is usually between 10-12k and MAP is 21" and at this point, with the MAP so low, can't hurt the engine at any mixture level.

Why do you run LOP at 10-12K?  Peak should provide more than adequate detonation margin and yields highest speed at best BSFC.  You're leaving some efficiency and speed on the table. Do you feel like it's kinder to your engine?

[Mufflerbearing]

53 minutes ago, Shadrach said:

Why do you run LOP at 10-12K?  Peak should provide more than adequate detonation margin and yields highest speed at best BSFC.  You're leaving some efficiency and speed on the table. Do you feel like it's kinder to your engine?

As the MAP is at 21" at this altitude, there is no red box to even think about, so there is no issues of what mixture may damage the engine.  So, I have played with all kinds of settings and at this setting, it is not any slower than burning 12.5 or 13gph and it keeps the oil clean, so why not?  Could I go faster by running more rich say 15 or 16gph, but I'm already flying a fast plane, why burn 3 gph or more to gain 3 knots?  Flying 200 hours a year x $6.00/gal (if only, right?) x 3gph = $3600/year in fuel savings but only spending 3 kts x 200 hours = 600 miles divided by 167 TAS =3.59 hours.  I can burn that kind of time for that kind of fuel savings.

[Shadrach]

19 minutes ago, Mufflerbearing said:

As the MAP is at 21" at this altitude, there is no red box to even think about, so there is no issues of what mixture may damage the engine.  So, I have played with all kinds of settings and at this setting, it is not any slower than burning 12.5 or 13gph and it keeps the oil clean, so why not?  Could I go faster by running more rich say 15 or 16gph, but I'm already flying a fast plane, why burn 3 gph or more to gain 3 knots?  Flying 200 hours a year x $6.00/gal (if only, right?) x 3gph = $3600/year in fuel savings but only spending 3 kts x 200 hours = 600 miles divided by 167 TAS =3.59 hours.  I can burn that kind of time for that kind of fuel savings.

I am not quite following here. It reads like you're saying that there is a 3gph delta between Peak EGT and whatever LOP setting you're using with little difference in speed loss?  That seems unlikely given that power tracks fuel flow at peak and beyond in a linear manner (generally speaking).  Good chance that I am misunderstanding you.

My only point was that in the BSFC curve of a normally aspirated engine is more or less flat after Peak EGT at any reasonable mixture setting.  I always try to run as close to the most power for the least amount of fuel as temps will allow. This means peak or as close to peak as possible on the lean side. 

[Ragsf15e]

1 hour ago, Shadrach said:

I am not quite following here. It reads like you're saying that there is a 3gph delta between Peak EGT and whatever LOP setting you're using with little difference in speed loss?  That seems unlikely given that power tracks fuel flow at peak and beyond in a linear manner (generally speaking).  Good chance that I am misunderstanding you.

My only point was that in the BSFC curve of a normally aspirated engine is more or less flat after Peak EGT at any reasonable mixture setting.  I always try to run as close to the most power for the least amount of fuel as temps will allow. This means peak or as close to peak as possible on the lean side. 

I usually fly that altitude too.  Maybe he’s saying it like I do but actually doing it closer to what you’re describing…

I use the “LOP” mode on my 930 so it shows each cylinder peak.  I then set the mixture so the last one is at peak and the others are slightly lean (~.3 gami spread).  So I call that lean of peak at 10k.  I realize I could probably set it so 2 cylinders are lean and 2 rich and probably not hurt anything, but temps work out best with setting the richest one at peak.

[Shadrach]

6 hours ago, Ragsf15e said:

I usually fly that altitude too.  Maybe he’s saying it like I do but actually doing it closer to what you’re describing…

I use the “LOP” mode on my 930 so it shows each cylinder peak.  I then set the mixture so the last one is at peak and the others are slightly lean (~.3 gami spread).  So I call that lean of peak at 10k.  I realize I could probably set it so 2 cylinders are lean and 2 rich and probably not hurt anything, but temps work out best with setting the richest one at peak.

I also use richest cylinder for peak. Regardless of what power setting is being used, I typically reference the cylinder with the lowest detonation margins for that setting. That way I know the rest are equal to or more conservatively set than referenced cylinder.

[A64Pilot]

There are compression variations from cylinder to cylinder they aren’t big but they are there, the lowest EGT cylinders at peak are your highest compression ones, as detonation is a function of mixture and compression, you should use your highest compression cylinder as the one you use to lean from, splitting hairs, but if your picking one it’s the most likely to detonate, may as well pick that one.

I know it seems the high compression would give you the highest EGT, but it’s just the opposite, high compression extracts more energy from the fuel burn and yields a lower EGT.

Fly with someone with the same, but lower compression motor, their peak will be about 100 degrees hotter it seems.

[Shadrach]

1 hour ago, A64Pilot said:

There are compression variations from cylinder to cylinder they aren’t big but they are there, the lowest EGT cylinders at peak are your highest compression ones, as detonation is a function of mixture and compression, you should use your highest compression cylinder as the one you use to lean from, splitting hairs, but if your picking one it’s the most likely to detonate, may as well pick that one.

I know it seems the high compression would give you the highest EGT, but it’s just the opposite, high compression extracts more energy from the fuel burn and yields a lower EGT.

Fly with someone with the same, but lower compression motor, their peak will be about 100 degrees hotter it seems.

It’s true that e.g. tees track compression but I don’t think the differences are significant enough to amount to more than noise. Probe position alone can have a significant effect on the actual number.

As for cylinder reference for leaning, The cylinder with the lowest margins is the one with the most aggressive mixture setting. If setting mixture on the rich side of peak EGT, the leanest cylinder (first to peak) is the safest cylinder to reference as all others will be richer. If mixture setting is peak or leaner, the richest cylinder (last to peak) is the safest cylinder to reference as all others will be leaner.  Whatever the mixture setting, it’s best if the remaining cylinders are known to be at a setting that is equal to or more conservative with regards to detonation margins than the referenced cylinder.