Flying over square for better fuel economy, how far over can TSIO-360 safely go?

[Will.iam]

9 hours ago, PT20J said:

The concern about running LOP at "high" powers is probably fear of detonation. Detonation is caused by heat. High cylinder pressures heat the mixture by compression and rapid burning of the charge causes the end gas to further heat by the compression by the advancing flame front. If the heating gets to the point of self ignition, the end gas combusts very rapidly with the pressure rise typical of detonation. 

John Deakin, before he quit flying after his stroke, used to cruise his turbo-normalized Bonanza LOP at 80+% power with CHTs at 380F or below. I have no idea what the long term effects may have been, good or bad. I understand some Cirrus guys do this, but I haven't hung out on the Cirrus site for a long time since I'm not flying a Cirrus any longer. I asked Mike Busch and he didn't have an opinion stating that he runs his 310 LOP at low (65% or less) powers because, "I'm a longevity guy, not a speed guy." I would really like to know the long term effects of "high" power LOP if anyone has a source of data rather than opinions.

Skip

I would love to know what dekin’s TIT was at 80% power LOP. Yea i could keep my CHT below 380 LOP too but my TIT would be real close to if not exceeding 1650. And maybe that’s what he did don't know. 

[A64Pilot]

17 hours ago, Shadrach said:

What is the operational reasoning for operating a NA engine that lean at those altitudes. I cannot think of an operational reason to run anywhere near 25° LOP at 10k or above with a NA engine..

An attempt to justify LOP operation in a Maule, A Maule has too much wing for efficient cruise at normal altitude, at least an M-6 does, as an attempt to spoil lift and increase cruise speed, the flaps reflex -7 degrees. It works, but isn’t the most efficient thing, but you want that excessive lift for 30’ish kt approaches. The effect of this excessive wing area is to move the best cruise altitude up from the normal 7.5K to 10 to 12k, a little testing confirmed at 12k that there was no speed difference between -7 floss and 0 flaps. 

So as you can imagine, LOP in a Maule was essentially a waste, lower altitudes where it made sense, the additional drag from the wing pretty much washed out any decrease in BSFC from LOP, so efficiency wise as far as MPG, run peak at between 10 and 12 thousand.

Maule would cruise at 135 kts true up there at I think about 12 GPH, down lower fuel burn increased for the same speed, higher fuel burn went down LOP but so did speed.

Now the 210 was a different story, LOP worked, but you lost speed so as I usually wasn’t buying fuel for it, it was rarely used, speed was more important. However if I ran 50 ROP and slowed to the identical airspeed that -25 LOP gave me, the fuel savings wasn’t really that great, certainly no where near 5 or 6 GPH, maybe 1 or so, but I think less.

So when comparing LOP to ROP fuel consumption wise, be sure speed is identical and use logical numbers like 50 ROP, not full rich.

Of course you will have to slow down, because you can’t cruise at ROP speeds LOP, the power just isn’t there.

Lycoming chart you posted show economy range being essentially from peak to -100 LOP, what’s wrong with -25 at altitude? Altitude shouldn’t really change LOP’s effect on BSFC, just the higher you go the more of a dog it becomes LOP

The 210, the Maule and my Mooney if your going a significant distance fuel wise mid altitudes are your friend, especially if time is relevant, you can run LOP, but at the cost of significant speed.

Using this program I use for determining % power cause I’m lazy give us 68.5% power at 7500 at 2300 RPM which is smooth and relatively quiet RPM, this chart is optimistic I believe as it doesn’t include airframe losses, but take 68 and roughly 5% from your Lycoming chart for loss from best power to peak puts us at 63% power, further leaner of course and power drops off even faster. But 63 is good because Lycoming says for longest life cruise at less than 65%

 So where does this leave us? It leaves us determining that most likely Joe average travels somewhere between 5 and 10,000 ft, and that at average traveling altitudes Lycomings recommendation of operating at peak makes sense, completely contrary to what you read so often.

Now most of my flying now days is just OFO and return to home and as I’m not going anywhere it’s at low altitudes, and I will run pretty deep LOP, about 50C and as I’m not going anywhere and have all day to get there 120 to 130 kts is fine, so I don’t have any issues against LOP, just for the average Joe who bought a Mooney largely for its speeds and traveling, LOP often isn’t logical for him or her, but it’s a tool and nothing wrong with having a full bag of tools, it may be that for instance running ROP can’t quite get you to destination while slowing down and LOP can, and due to a missed fuel stop going slower is actually faster.

Edited May 2, 2022 by A64Pilot

[Fly Boomer]

10 hours ago, Will.iam said:

I would love to know what dekin’s TIT was at 80% power LOP. Yea i could keep my CHT below 380 LOP too but my TIT would be real close to if not exceeding 1650.

I once asked him about my "go high, go fast, LOP" aspirations for my M20K, and he said it may not work as well as I hoped.  I asked why, and his one-word answer was "heat" (I guess he wasn't feeling very talkative).

[Shadrach]

1 hour ago, A64Pilot said:

An attempt to justify LOP operation in a Maule, A Maule has too much wing for efficient cruise at normal altitude, at least an M-6 does, as an attempt to spoil lift and increase cruise speed, the flaps reflex -7 degrees. It works, but isn’t the most efficient thing, but you want that excessive lift for 30’ish kt approaches. The effect of this excessive wing area is to move the best cruise altitude up from the normal 7.5K to 10 to 12k, a little testing confirmed at 12k that there was no speed difference between -7 floss and 0 flaps. 

So as you can imagine, LOP in a Maule was essentially a waste, lower altitudes where it made sense, the additional drag from the wing pretty much washed out any decrease in BSFC from LOP, so efficiency wise as far as MPG, run peak at between 10 and 12 thousand.

Maule would cruise at 135 kts true up there at I think about 12 GPH, down lower fuel burn increased for the same speed, higher fuel burn went down LOP but so did speed.

Now the 210 was a different story, LOP worked, but you lost speed so as I usually wasn’t buying fuel for it, it was rarely used, speed was more important. However if I ran 50 ROP and slowed to the identical airspeed that -25 LOP gave me, the fuel savings wasn’t really that great, certainly no where near 5 or 6 GPH, maybe 1 or so, but I think less.

So when comparing LOP to ROP fuel consumption wise, be sure speed is identical and use logical numbers like 50 ROP, not full rich.

Of course you will have to slow down, because you can’t cruise at ROP speeds LOP, the power just isn’t there.

Lycoming chart you posted show economy range being essentially from peak to -100 LOP, what’s wrong with -25 at altitude? Altitude shouldn’t really change LOP’s effect on BSFC, just the higher you go the more of a dog it becomes LOP

The 210, the Maule and my Mooney if your going a significant distance fuel wise mid altitudes are your friend, especially if time is relevant, you can run LOP, but at the cost of significant speed.

Using this program I use for determining % power cause I’m lazy give us 68.5% power at 7500 at 2300 RPM which is smooth and relatively quiet RPM, this chart is optimistic I believe as it doesn’t include airframe losses, but take 68 and roughly 5% from your Lycoming chart for loss from best power to peak puts us at 63% power, further leaner of course and power drops off even faster. But 63 is good because Lycoming says for longest life cruise at less than 65%

 So where does this leave us? It leaves us determining that most likely Joe average travels somewhere between 5 and 10,000 ft, and that at average traveling altitudes Lycomings recommendation of operating at peak makes sense, completely contrary to what you read so often.

Now most of my flying now days is just OFO and return to home and as I’m not going anywhere it’s at low altitudes, and I will run pretty deep LOP, about 50C and as I’m not going anywhere and have all day to get there 120 to 130 kts is fine, so I don’t have any issues against LOP, just for the average Joe who bought a Mooney largely for its speeds and traveling, LOP often isn’t logical for him or her, but it’s a tool and nothing wrong with having a full bag of tools, it may be that for instance running ROP can’t quite get you to destination while slowing down and LOP can, and due to a missed fuel stop going slower is actually faster.

So my POH recommends against leaning in any way below a DA of 3000'.  Like most POH recommendations, the logic behind this is reasonable. It was a simple way to help LBJ era pilots stay out of trouble with minimal understanding and instrumentation.  Leaning at high power can be safe, but it is one of those things that if you have to ask about it, it's probably best that you don't do it.

I think your location maybe coloring your view.  In my neck of the woods, 3000' DA can translate to ~6000msl in the winter months. I make a lot of regional flights that take an hour or less. I also have one of the busiest and most restrictive airspace sectors to contend with. For example, If I want to fly down to Annapolis for dinner with friends, it's ~30min flight. In the car, it's 1:45 with no traffic...which almost never happens.  The bottom of the Bravo shelf for much of the flight is 2500msl.  So, I can pull back to 70% or less and take 155ish MIAS (10.5 ROP or 9.3 LOP).  If I run WOTRMO ROP (>175MIAS), I am going to need a minimum of 15GPH to keep temps where I want them.  I'd never run it like that.  WOTRAO LOP is around 11ish GPH with cool CHTs, smooth running engine, and airspeed still north of 170MIAS. 

 

[A64Pilot]

Your F will make over 175 kts?

Max I could get out of my J on the pre-purchase flight was 168 kts everything forward and altitude 1,000 ft. which of course would be very foolish to try to maintain, and fuel flow was 19 GPH

Realistic cruise speed is closer to 155 kts, I didn’t know an F was so much faster than a J

OK so Statue as opposed to Nautical?

I would say your use case is actually the unusual one, most don’t have to complete flights under airspace, most I maintain fly between 5 and 10K NA airplanes anyway

 10 to 12 in the Maule was actually nice and low traffic, above most small aircraft, yet below the turbos and big boys.

‘I only have factory fuel flow, factory EGT single probe temp and factory Cyl head temp, yet maintain LOP is safe if conducted below 65% power, I actually think you could push that to 75% as Lyc charts are at best power and LOP is less so long as your pretty lean 75 turns into 65 pretty quick but I don’t, just isn’t worth it

On edit, I never cruise above 75% and rarely even 75%. I climb at max power of course, but power drops off as soon as you climb and at cruise I back off RPM at least 

‘I understand the desire being well instrumented, back to the Maule I had a multi point calibrated MVP-50, but the way I fly truth is it would never pay for itself, not even close.

Neat toy to play with though and probably dropped a little weight.

Edited May 2, 2022 by A64Pilot

[Shadrach]

1 hour ago, A64Pilot said:

Your F will make over 175 kts?

Max I could get out of my J on the pre-purchase flight was 168 kts everything forward and altitude 1,000 ft. which of course would be very foolish to try to maintain, and fuel flow wax 19 GPH

Realistic cruise speed is closer to 155 kts, I didn’t know an F was so much faster than a J

OK so Statue as opposed to Nautical?

I would say your use case is actually the unusual one, most don’t have to complete flights under airspace, most I maintain fly between 5 and 10K NA airplanes anyway

 10 to 12 in the Maule was actually nice and low traffic, above most small aircraft, yet below the turbos and big boys.

‘I only have factory fuel flow, factory EGT single probe temp and factory Cyl head temp, yet maintain LOP is safe if conducted below 65% power, I actually think you could push that to 75% as Lyc charts are at best power and LOP is less so long as your pretty lean 75 turns into 65 pretty quick but I don’t, just isn’t worth it

‘I understand the desire being well instrumented, back to the Maule I had a multi point calibrated MVP-50, but the way I fly truth is it would never pay for itself, not even close.

Neat toy to play with though and probably dropped a little weight.

My bird is a 67...ASI is in MPH.  If you look at my post I clearly use MIAS as a suffix.  MIAS = Indicated airspeed in MPH. 

It's an honest 173mph (150kt) airplane under most conditions.  I can push it close to180 down low under certain conditions but not using any practical cruise setting. I am sure all other things being equal, that most Js are faster, some might be significantly faster.   In terms of real world block speeds, the differences between all 4 cyl Mooneys are more about bragging rights than meaningful difference travel times.

Edited May 2, 2022 by Shadrach

[A64Pilot]

Mine can get 155, but I’m usually 130ish or so, because the MPG goes up significantly, and 130ish is enough for me, plus it keeps me at low power which is good for engine longevity. I don’t plan on overhauling this engine, ever. It’s about 300 SMOH and I probably have 10ish years left flying, but even if it were 15, I still won’t likely be at TBO

[carusoam]

12 hours ago, A64Pilot said:

I don’t plan on overhauling this engine, ever. It’s about 300 SMOH and I probably have 10ish years left flying, but even if it were 15, I still won’t likely be at TBO

Isn’t Loki the god of mischief? He likes statements like this….  

Soooo many good Mooney flying years to come…

Keep Loki at bay…

-a-

[A64Pilot]

Yeah I know the cam worries me just like it did in the Maule.

But I did say I’m not planning, I didn’t say I won’t, Murphy has a vote too, or no plan ever survives contact with the enemy

[Fly Boomer]

1 minute ago, A64Pilot said:

no plan ever survives contact with the enemy

Good to have a plan, but we all know it's not going to go that way.

[A64Pilot]

7 minutes ago, Fly Boomer said:

Good to have a plan, but we all know it's not going to go that way.

You don’t think a Lyc will reach close to TBO? I think most do and some go well past

I have a couple of theories about cams, one of them is that excessive blow by plays a part and another is that some number of cams are just bad, meaning if you have one of those it’s going to fail, pretty much no matter what you do or don’t do, but most cams aren’t bad or go bad, I have no idea of failure rate.

Be nice if there was a database on failed cams so we could see if date of manufacture or number of hours or maybe number of regrindings or maybe of reground vs new or whatever had clusters of failures.

Edited May 3, 2022 by A64Pilot

[Fly Boomer]

7 minutes ago, A64Pilot said:

You don’t think a Lyc will reach close to TBO?

I was referring to your statement that "no plan ever survives contact with the enemy" and, throughout my life, I have found that to be true in many endeavors.  Some Lycs will fail halfway to TBO, and some will go to twice TBO.  We have a lot of speculation regarding the "why", but I suspect it remains one of the secrets of the universe.  I help another old guy do his compression checks on his 540 that is way past TBO, and they are always way up into the 70s.  I'm not that impressed with his maintenance philosophies, but you can't argue with success.

[Pinecone]

https://gami.com/articles/baconsbonus.php

Here are some photos taken in an Aerostar where one engine was running LOP and one running ROP.  Both making the same power (no yaw).  4.5 - 4.6 GPH less fuel flow LOP.

With NA engine, you run into the issue where you need to run ROP for the power to get the speed.

If you read Deakin's Pelican Perch articles on AVWEB, he points this out.

[A64Pilot]

I think a lot of the issue is we are flying old engines and old tech designs, manufacturing etc.

If we go back in the day old car motors didn’t last long either, but 21st Century automobiles are pretty much bullet proof, I have a tendency to over maintain, but I have never worn out a motor, not lawnmower, motorcycle, boat, car etc. I did wear out a chainsaw once, plating came off the cylinder.

I usually replace vehicles when the rest of the vehicle just gets old, paint chipped and faded, everything squeaks, interior is worn etc, but motor and xmsn are fine. Before I went cruising I sold a 574 International tractor that had been in the family since late 70’s. Had over 7,000 hours on it and did burn some oil, but it started instantly and made good power. It’s oil had been changed every 100 hours.

‘So we have come to expect that kind of life expectancy, and our aircraft engines don’t deliver.

I did see a 14,000 hour PT6-34Ag once, poor thing was so down on power it just couldn’t do the job anymore, but it did make it to 14,000 hours, airplane was about shot too.

[Fly Boomer]

5 minutes ago, A64Pilot said:

I have never worn out a motor, not lawnmower, motorcycle, boat, car etc. I did wear out a chainsaw once, plating came off the cylinder.

I usually replace vehicles when the rest of the vehicle just gets old, paint chipped and faded, everything squeaks, interior is worn etc, but motor and xmsn are fine.

Couldn't agree more.  Now I drive a Prius that looks pretty good but, for most of my life, I drove cars that looked like beaters, but I wouldn't hesitate to drive across the country.

[Will.iam]

35 minutes ago, Fly Boomer said:

I was referring to your statement that "no plan ever survives contact with the enemy" and, throughout my life, I have found that to be true in many endeavors.  Some Lycs will fail halfway to TBO, and some will go to twice TBO.  We have a lot of speculation regarding the "why", but I suspect it remains one of the secrets of the universe.  I help another old guy do his compression checks on his 540 that is way past TBO, and they are always way up into the 70s.  I'm not that impressed with his maintenance philosophies, but you can't argue with success.

Can you ask the guy how he flew his plane? Just curious if he flew it hard or was easy on the power. 

[Fly Boomer]

2 minutes ago, Will.iam said:

Can you ask the guy how he flew his plane? Just curious if he flew it hard or was easy on the power. 

I have ridden with him, and I can't really say much about how he flies it (nor can he) because he has no engine monitor.  He pays attention to the gauges, but they don't have any numbers.  It's a NA Comanche, but he likes to get up to 15,000 or 16,000 on long cross countries.  Not going super fast, but not burning much gas either.  All I can say is "you can't argue with success" -- whatever he does is working for at least that particular engine.

[Fly Boomer]

1 hour ago, mike261 said:

"Everyone got a plan till they get punched in the mouth" - Mike Tyson

Yeah, that's the kind of thing I'm talking about.  That really made me laugh!

[Shadrach]

4 hours ago, A64Pilot said:

You don’t think a Lyc will reach close to TBO? I think most do and some go well past

I have a couple of theories about cams, one of them is that excessive blow by plays a part and another is that some number of cams are just bad, meaning if you have one of those it’s going to fail, pretty much no matter what you do or don’t do, but most cams aren’t bad or go bad, I have no idea of failure rate.

Be nice if there was a database on failed cams so we could see if date of manufacture or number of hours or maybe number of regrindings or maybe of reground vs new or whatever had clusters of failures.

Bad cam is my theory as well.  Mine is 55 years old and has 3300 hours.   The first 30 years of its life, it only saw 1800 hours and flew less than 5hrs some years. No spalling when overhauled in 2000. Engine IRAN'd in 2011 at 950SMOH due to a case crack...No spalling.  It's flown regularly now and is treated with camgaurd, but given all the theories on Lycoming cam life, its previous usage history should have led to premature failure.  For what ever reason some Lycoming cams are not robust.

I think rollers will prove a good solution.  They seem to have eliminated cam wear in vehicles.  I pulled the valve cover on my 3 series to replace the gasket a few weeks back. There is no visible wear (not even staining) on the cams after 13 years and 190K miles.

[A64Pilot]

Rollers are in vehicles mostly due to modern oil not having the anti wear additives that used to keep flat tappets alive, and partially for less friction. ZDDP, it would I believe fix our problems, but it’s not ashless, and I don’t think was ever in aircraft oil.

But you know some experimental guys have to be running it

Rollers should be a solution, but require a new case I believe and for me new mags as well.

A question is it the tappets or the cam? one will chew up the other of course.

Who knows 

[Fly Boomer]

8 minutes ago, A64Pilot said:

is it the tappets or the cam? one will chew up the other of course.

I have seen a recommendation to replace lifters in a Continental at the first sign of trouble.  Doesn't answer the question, but they are fairly easily replaced, and it could head off bigger problems.

[Shadrach]

20 minutes ago, Fly Boomer said:

I have seen a recommendation to replace lifters in a Continental at the first sign of trouble.  Doesn't answer the question, but they are fairly easily replaced, and it could head off bigger problems.

I wish this possible with a Lycoming without splitting the case as the lifters typically go first. I replaced all the lifters when overhauled the case. The were serviceable but under magnification there was evidence of surface irregularities. replacing was cheap insurance.

[carusoam]

What we are getting a better feel for around here….

When a cam goes bad… the follow up question is what do the followers look like?

The answer is always a cratered surface…

The cratered surface is unable to be lubricated with oil… 

So it cuts down the cam lobe instead….

 

Oddly, this appears most often in the Lycoming IO360… but, the IO540 doesn’t seem to have the same challenge…

A few IO550s have gotten new followers… fortunately they didn’t  require a tear down for that…

 

There must be some really red hot surfaces right after start-up on engines that have had the oil run off every surface…

 

How many rotations does it take to get oil to the cam… with a dry engine?

Oil to the bearings must happen quite quickly by comparison…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

[A64Pilot]

IO and O 540’s eat cams too as well as O-320’s

Maybe the Antique Lycomings don’t?

Cam isn’t oiled, it’s splash lubricated. I think some have been drilled for oiling, but that must have not made a difference.

‘I believe nozzles have been added to spray oil on the cam as well

On edit, about every logical cure has been tried, leaving I believe possibly there being some number of bad cams or lifters, maybe with subsurface inclusions or something

Edited May 4, 2022 by A64Pilot