Power setting LOP

[PT20J]

40 minutes ago, Shadrach said:

Are the 201 gauges not wet? On my F, swapping these over under at the firewall will do exactly what you suggest. Oddly the threads are the same size but the fittings take different size wrenches. You can see that I faintly “sharpied” the fire wall to avoid a potential mix up.

Not sure about the 1977s. My 1978 had electric gauges as does my 1994.

[A64Pilot]

As mine don’t work with the Master off I’m fairly sure they are electric, positive actually as I’ve seen the back side of them. 81 J

If they are like I think they are they aren’t individual gauges, but a cluster, which of course is no longer obtainable. It works, it’s in the green barely, I’m not mucking with it. I know it works because if I leave the red knob out 15 min or so after shutdown the fuel pressure is astonishingly high so I’ve gotten in the habit of pushing the red knob in after shut down and bleeding the pressure off then of course pulling it back out.

Knowing it works of course does not mean it’s accurate.

Where is the transducer located anyway?

Master off in my airplane literally leaves you with an artificial horizon, tach and MP gauge, standby compass and nothing else.

I used to have a dead weight tester, with that verifying its accuracy would be simple.

[PT20J]

2 hours ago, A64Pilot said:

Where is the transducer located anyway?

Location varies. There is a hose that comes off the servo inlet and the transducer is at the other end of the hose.

[Pinecone]

On 12/30/2023 at 7:06 PM, Shadrach said:

Was the aircraft equipped with a multi cylinder engine monitor? 

Too bad Churchville doesn’t have longer runways. They could conservatively limit power to 65% for all operations and avoid destroying cylinders…

No, it does not.  But carb, so hard to get one cylinder really wonky, but it did happen.

We have gone from 2850 to 3350 and have projects to get to 4250.  But if you look Google maps and the sat view, the picture if at least a year old.  The runway has been extended as far as possible to the south now.  You can't see but that end of the runway is maybe 20 feet above the road, and current requirements need a sloped section to the threshold.  Not cliffs.  The threshold on that end is displaced for now due to the power lines.  They are going to be buried, but a LONG story, but it has been in progress for over 3 years.

To the north, the displaced threshold is also due to power lines along the road, that are in the process of being buried.  I think they will also pave some additional runway in that direction and add taxiway and runup area.

We are loosing 10/28.  It is short and narrow.  Too bad, even at 2000 feet, it is a nice backup when the main runway has 20 knots or more of crosswind.  I learned at this airport on that 2000-foot runway, flying AA-5B Tigers.

[PT20J]

1 hour ago, Pinecone said:

No, it does not.  But carb, so hard to get one cylinder really wonky, but it did happen.

That was most likely preignition. Not likely to get detonation in a carbureted engine at full rich.

[Shadrach]

39 minutes ago, PT20J said:

That was most likely preignition. Not likely to get detonation in a carbureted engine at full rich.

Agreed. I like to think that a full complement of CHT information would have given the pilot the cues they needed to prevent permanent damage.

[EricJ]

39 minutes ago, PT20J said:

That was most likely preignition. Not likely to get detonation in a carbureted engine at full rich.

Yeah, chunk of carbon or broken plug nose or something like that.

[A64Pilot]

5 hours ago, PT20J said:

That was most likely preignition. Not likely to get detonation in a carbureted engine at full rich.

Did someone say full rich? I’ve never heard of detonation or pre-ignition full rich.

I’ve seen it happen on an airplane left leaned out and the pilot forgot to push the red knob back in, shot a touch and go and a few minutes into the climb heard the rattle, by then the damage was done.

It’s odd though on every engine I’ve seen detonated to death it’s always one cylinder and not multiples. My Brother detonated the IO-520 to death. because he didn’t know what he was doing and was too lean for the power he was running.

Even if he knew how LOP wasn’t an option at the speeds he was trying to make.

Odd thing is the cars of the late 70’s would rattle like hell pulling a hill, but it never hurt anything?

[Shadrach]

15 minutes ago, A64Pilot said:

Did someone say full rich? I’ve never heard of detonation or pre-ignition full rich.

I’ve seen it happen on an airplane left leaned out and the pilot forgot to push the red knob back in, shot a touch and go and a few minutes into the climb heard the rattle, by then the damage was done.

It’s odd though on every engine I’ve seen detonated to death it’s always one cylinder and not multiples. My Brother detonated the IO-520 to death. because he didn’t know what he was doing and was too lean for the power he was running.

Even if he knew how LOP wasn’t an option at the speeds he was trying to make.

Odd thing is the cars of the late 70’s would rattle like hell pulling a hill, but it never hurt anything?

If you lug an old car Into detonation for a long enough period of time, you can hole a piston.

Your brother didn’t beat up that IO550 because he was too lean.  He beat it up because he wasn’t sufficiently lean nor sufficiently rich. When I first started reading aviation literature in my teens (1990s), 50ROP was a popular mixture setting. The thinking being that it was a nice “compromise” between best power (100ROP) and best economy (peak). If detonation is the goal, 50 ROP is good starting point.

[A64Pilot]

57 minutes ago, Shadrach said:

If you lug an old car Into detonation for a long enough period of time, you can hole a piston.

Your brother didn’t beat up that IO550 because he was too lean.  He beat it up because he wasn’t sufficiently lean nor sufficiently rich. When I first started reading aviation literature in my teens (1990s), 50ROP was a popular mixture setting. The thinking being that it was a nice “compromise” between best power (100ROP) and best economy (peak). If detonation is the goal, 50 ROP is good starting point.

I know that, that’s why I said even if he knew how LOP wouldn’t have given him what he wanted which was to keep up with me, it was an IO-520 though and not a 550, a 300 HP 520, except your wrong on the 50 ROP, it’s a mixture that as long as you follow Lycomings directions and don’t lean above 75% power it’s a mixture that still gives good power, it’s a perfectly acceptable mixture and Lycomings have been running it and living long lives for far longer than any of us have been pilots.

In fact follow Lycomings directions and you will never hurt a motor.

You know though that I almost always cruise LOP.

120 KIAS I get 20 NMPG

135 KIAS I get 16.87

155 KIAS based on just about every magazine article I would get 14.7 NMPG, the 155 the mags quote is I’m sure ROP, because I doubt the average J can cruise 155 KIAS LOP. Yeah I know some are sure theirs will run 165 KIAS, but I suspect that’s Knots Internet Air Speed.

Do you see a trend? Sure LOP saves some fuel, but the primary fuel savings is from speed reduction.

One big thing that always seems to be ignored, and that’s only a fraction of the GA fleet is even capable of LOP, GAMI made some that were close capable but usually just barely, even with a small GAMI spread many engines just won’t run LOP most of the time, my 540 wouldn’t very well, just barely. The majority of the fleet when they lean to roughness then slowly enrichen end up often about 50 ROP but as they aren’t balanced it’s usually cylinders scattered from about peak to 50 ROP, and they do fine, so long as they don’t try it at high manifold pressure.

However back before flat motors most everyone ran round motors LOP, especially the Supercharged ones. The “new way” to operate engines isn’t new, it’s 100 years old. You can see a round motor st night go LOP by watching it’s exhaust color

Lycoming has a reputation to live up to, and it’s not one of being a dog, it’s one of making power, so they have never recommended a mixture that gives up too much power, if they did I’m sure they thought people would complain.

Not beating on Continental, but I only can think of one race plane class with Continentals, no Aerobatic aircraft, and the real tell to me is no Helicopters.

To detonate it takes among other things heat and a big reason being ROP or LOP enough prevents detonation is there isn’t enough heat.

However going real rich wastes fuel but the power drop off is slight, go lean of peak and the power drops drastically.

Thats the one reason we take off and climb ROP. It’s perfectly safe to do so IF, and that’s a BIG if, but if your engine will run LOP enough to prevent detonation. The problem is it would be a dog, serious decrease in performance.

However it’s a rare motor that will run that lean, our angle valve Lycomings will but even in Lycomings it may be the only one that will.

Years ago in my Maule I ran a simple test point, at my usual cruise altitude of between 10 and 12 thousand I ran LOP at full throttle and 2200 RPM (redline on that motor was 2400) it’s wasn’t but maybe 20 LOP it wouldn’t go any deeper.

Anyway then adjusted mixture to 50 ROP and reduced throttle until I was at the exact airspeed, if memory serves the difference in fuel flow was less than 1 GPH.

That airplanes engine was only a couple hundred hours after overhaul with Gami injectors and fine wire plugs and I had a MVP-50 so it was as equipped for LOP as was possible.

I flew high because a Maule had too much wing for performance cruise and while you lose HP with altitude you lose drag even faster up to a point, that point for an M6 Maule was between 10 and 12 thousand feet. I used to do a lot of long cross countries in that airplane.

One day I might do that in the Mooney just to see, maybe the Mooney is different

However you have to ensure airspeeds are identical, if they aren’t then it’s not an apples to apples comparison. As you lose power LOP that’s why I say run that test full throttle, and truthfully your giving LOP a little advantage by being full throttle your reducing its pumping losses.

My best mileage is 120 KIAS of course but who can fly that slow? I do sometimes when I’m in a group of slow airplanes, but my go to cruise is 8 GPH 23 squared which gives me 135 KIAS good fuel milage and at 60% power it’s below the number that Lycoming recommends for maximum engine life, because I hope to never have to buy an overhaul, and if I take care of it I won’t have to, that’s a function of being old.

One day you realize you don’t have a need for a 30 year roof anymore.

[Pinecone]

According to GAMI, the best place to run is actually very light detonation.

New cars run near this condition.

[A64Pilot]

11 minutes ago, Pinecone said:

According to GAMI, the best place to run is actually very light detonation.

New cars run near this condition.

Yes, well at higher power they do, in fact they have a sensor that adjust timing to achieve a point just prior to detonation.

A “knock” sensor. 

It’s why higher power cars will actually get better fuel milage on high octane gas.

The average grocery getter won’t though because they won’t approach detonation most times, in fact as premium car gas flame front spread is slightly slower having a similar effect to reducing timing, they may actually get slightly less mileage on premium.

That's ignoring ETH or ethanol fuel, whike it does increase octane it’s BTU per volume is much less than gasoline.

I used to hyper mile our Prius years ago as a game, and ETH fuel dropped milage by a significant margin, 10% almost if memory serves. It took a hit on ETH free Premium too

72.6 MPG was the best I ever got and that was no traffic back country roads using every trick I knew.

 

 

[PT20J]

1 hour ago, Pinecone said:

According to GAMI, the best place to run is actually very light detonation.

New cars run near this condition.

I don't believe George Braly said that. What I did hear him say is that some engines he has tested seem to run in light detonation without damage and that the Wright R-3350 operated continuously that way.

[Shadrach]

I have tried to provide counter points to what I consider to be misstatements made in this thread that are not supported by well understood data. This has happened in other engine management threads as well. If anyone has questions or corrections regarding anything I have said here, feel free to pm me. I’m going to stop banging my head against this particular wall.

 

[PT20J]

1 hour ago, A64Pilot said:

To detonate it takes among other things heat and a big reason being ROP or LOP enough prevents detonation is there isn’t enough heat.

This is an excellent point. Operating very rich at high power prevents detonation by providing additional cooling. Detonation occurs when the last portion of the unburned fuel-air mixture (called the end gas) has been heated to the temperature where it spontaneously ignites. The heat comes from CHT, from the portion of the mixture already enflamed and from the rate of pressure increase (the latter being why advanced timing causes detonation). When the combination hits the magic temperature it knocks.

An important design parameter for aircraft engines is high power to weight ratio. No extra weight is given for cooling beyond what is necessary for normal cruise power. At higher powers with mixtures near stoichiometric, the engine is not able to reject all the heat of combustion and the temperatures will rise unacceptably. Adding excess fuel slows the rate of combustion and reduces the heat transferred to the cylinders. It does not significantly reduce the power output because (in chemistry terms) the added fuel increases the amount of substance (molecules of unburned gasoline + products of combustion + intermediate products of incomplete combustion) in the cylinders which expands due to the heat and produces the useful work of moving the pistons. Lean of peak, there is also slower combustion which reduces heat, but there is less substance in the cylinders to expand and produce useful work and thus lower power output.

George Braly told me that he has never been able to get a normally aspirated engine to detonate at CHTs of 400 deg F or less. Another interesting fact about light to moderate detonation is that it is difficult to see on an engine monitor because the extreme increase in temperature and pressure that causes piston damage is so short lived that it usually doesn't transfer enough additional heat to the cylinders to raise CHT and it also doesn't affect power output much. George can tell that a cylinder is detonating because he has outfitted it with a pressure transducer and can see the characteristic high frequency pressure variations. Preignition, on the other hand, has a definite signature of very rapid CHT rise (on the order of 1-2 deg F/sec, usually accompanied by a decrease in EGT. Also, you can feel the engine run rough because the early ignition means that the cylinder pressure before TDC is very nearly that after TDC and the power output of that cylinder is very low. Very heavy detonation can cause a similar effect.

Charles Fayette Taylor's Internal Combustion Engine in Theory and Practice, Vol. 2 has an entire chapter devoted to detonation.

[A64Pilot]

9 hours ago, Shadrach said:

I have tried to provide counter points to what I consider to be misstatements made in this thread that are not supported by well understood data. This has happened in other engine management threads as well. If anyone has questions or corrections regarding anything I have said here, feel free to pm me. I’m going to stop banging my head against this particular wall.

 

You keep inferring that I have said that you can get into detonation at High MP’s running LOP, when I have never said that.

What I continue to say is that running high MP or power if you will can get you into detonation if you mistakenly let the mixture enrichen by just a tad, best BSFC is just LOP, by what about 20F or so? If you let the mixture enrichen by 20F which isn’t much that puts you at peak or just rich of you can get into detonation.

As has been said in this thread by someone other than me  if you run high power LOP you had best better know what your doing,,and that is correct.

Anyone who comes on an internet forum asking rather basic questions about mixture and LOP doesn’t know what they are doing and advising them to run high power LOP is irresponsible.

Detonation damage can occur very quickly, I’ve detonated a drag bike to death on an 8 sec pass and never heard or felt anything, and it probably only detonated for a second or two, and it had Wiseco forged “blower” pistons, it went lean because the fuel couldn’t drain out of the tank fast enough.

Everything about flying and life in general is risk assessment, I don’t fly VFR with a poor vis because it’s not worth the risk, sure I could probably do it safely, I’ve flown helicopters in 100 &1/4 day 300 &1/2 half at night and crop dusters special VFR often enough but not since it’s not my job, the risk isn’t worth it just pleasure flying.

Most who smoke don’t die from cancer, you can’t truthfully say they will, but some do and to me the risk wasn’t worth it so I quit over 30 years ago.

So I don’t operate over 75% power LOP, and I cruise at less than 65% power because Lycoming says the engine will last longer if I do, regardless of mixture. However I do cruise LOP because I’m blessed with Lycoming’s poster child engine for LOP ops and there are advantages, I’ve had my Mooney for coming up on three years and still haven’t cleaned the plugs. I pull and inspect of course, rotate them and re-install. Couldn’t do that if I were ROP.

I’ve never said you’ll shoot your eye out running LOP, but I do say you can running high power LOP, if your not careful

I actually advise against high power cruise, but concede there are those that bought a Mooney to go fast and have the funds so that money isn’t an issue, but for them 100 ROP is their mixture or should be because no other mixture can make as much power.

All this assumes the Lycoming angle valve NA motor, turbo recips I don’t have experience with.

 

[T. Peterson]

On 12/29/2023 at 7:29 PM, BlueDun said:

That's right. You are lean of peak at that fuel setting and with that airflow. If your cylinder temps look good -- which you verified -- it's a good plan. It's *roughly* 70%. You then verified the setting with good engine temps. If you had stayed rich, you would have been closer to 75%, I think. It's good to have simple go-to settings. I highly recommend it. 

I took this course and am thoroughly comfortable setting my engine in different ways:

https://www.advancedpilot.com/onlinecourse.html

THAT SAID, no need to over think: 95% of the time i keep it really, really simple and fly. I climb for full power (which may mean some leaning for high altitude), stay wide open throttle and pull mixtures straight back to 13 or 13.5 gph for cruise, and then monitor CHT. (IO550 in an Ovation 3). That gives me 60- 65%, roughly.

Hope this helps you as you learn. 

 

 

I really like your simple approach. A lot on this thread just makes me dizzy!

 I very interested in the Ovations and am about to put up my 231 for sale, however I am very curious about the speed/efficiency gains and losses I can expect from such a move.

What is your TAS at 13 to 13.5 gph? And at what altitude? One of the reasons I want a normally aspirated engine is because I never fly above 12000 feet, but I do want speed and efficiency (who doesn’t!) I think the IO 550 will give me the best performance compromises, but I assumed that it would cost me 15 to 16 gph to get 175 kts vs the 12.5 to 13.0 I currently spend to achieve 160 kts.

[Austintatious]

On 12/29/2023 at 2:44 PM, wombat said:

So if my full power fuel flow is 33 GPH, then anything less than 24.75 GPH is less than 75% power.    So is it impossible to hurt my engine (regarding LOP operations, assuming the MAP and RPM are acceptable values) if my fuel flow is less than 24.75 GPH?

Wombat,

I thought I might give you some info to think about from a fellow rocket operator... In fact, I have 2.

 

First off, You could absolutely hurt your engine, specifically the turbo at fuel flows less than 24 GPH... or even 18 GPH... You are not automatically safe based on a fuel flow.

I have given up on LOP operations for the TSIO520NB.  I know Mike Bush runs LOP but his engines are different even though they are TSIO520s.  For starter they dont have the same big ol turbo charger that the rocket does but instead 2 smaller.

I have had so many adjustments from gami, to get anymore I would have to start paying Extra... and it seems every time an adjustment is made, it never has the intended effect.   I have replaced rubber seals each time and have pulled my hair out to get to a gami spread of about .6  and still the engine gets to rough running before getting truly established in LOP operation.  And I expect that to change just because of how "finicky" these fuel systems are. The slightest changes can have big effects on the cylinder balance... for instance the last time I had an annual done and they removed the injectors for cleaning, everything went WAY out of wack.

And the real kicker is that anything higher than about 9000 feet, you cant keep the TIT within limits if you go lean, and still I am into rough running.

So, what do I do?  I run 29/22 at about 16.5GPH... this puts the TIT at about 1550 and the hottest CHT (#5) at 360-370 and I will do about 147 IAS.  This will put me around 200 KTAS at FL180 depending on temp.  I can also run 31/22 @ 18.5GPH and keep everything in the green while doing about 5-7 knots faster, but I do not feel it is worth it.

In short, I feel that just pulling the power back in ROP operation saves as much fuel as messing with LOP.  I would be much further ahead if I had never even started down this road of attempting to get to a point of running LOP.  Especially considering that LOP cost a LOT of speed which you may not be wise to do if you are fighting a headwind.

 

Cheers.

[Shadrach]

11 hours ago, Austintatious said:

Wombat,

I thought I might give you some info to think about from a fellow rocket operator... In fact, I have 2.

 

First off, You could absolutely hurt your engine, specifically the turbo at fuel flows less than 24 GPH... or even 18 GPH... You are not automatically safe based on a fuel flow.

I have given up on LOP operations for the TSIO520NB.  I know Mike Bush runs LOP but his engines are different even though they are TSIO520s.  For starter they dont have the same big ol turbo charger that the rocket does but instead 2 smaller.

I have had so many adjustments from gami, to get anymore I would have to start paying Extra... and it seems every time an adjustment is made, it never has the intended effect.   I have replaced rubber seals each time and have pulled my hair out to get to a gami spread of about .6  and still the engine gets to rough running before getting truly established in LOP operation.  And I expect that to change just because of how "finicky" these fuel systems are. The slightest changes can have big effects on the cylinder balance... for instance the last time I had an annual done and they removed the injectors for cleaning, everything went WAY out of wack.

And the real kicker is that anything higher than about 9000 feet, you cant keep the TIT within limits if you go lean, and still I am into rough running.

So, what do I do?  I run 29/22 at about 16.5GPH... this puts the TIT at about 1550 and the hottest CHT (#5) at 360-370 and I will do about 147 IAS.  This will put me around 200 KTAS at FL180 depending on temp.  I can also run 31/22 @ 18.5GPH and keep everything in the green while doing about 5-7 knots faster, but I do not feel it is worth it.

In short, I feel that just pulling the power back in ROP operation saves as much fuel as messing with LOP.  I would be much further ahead if I had never even started down this road of attempting to get to a point of running LOP.  Especially considering that LOP cost a LOT of speed which you may not be wise to do if you are fighting a headwind.

 

Cheers.

The TIT limits and the inherent  imbalances in the fuel/intake system are what cost you speed. Not your mixture setting. Most applications were not designed with an eye towards the precision needed for LOP operations. Many turbocharged applications run fine on the lean side of peak. However, turbonormalized applications are better suited because their higher compression ratios generate lower TITs. See two TN’d IO540s below making same horsepower at the same RPM. Manifold pressure and TIT is lower on ROP engine (L side) while CHTs and fuel burn are higher. Manifold pressure and TIT is higher on LOP engine (R engine) while fuel burn and CHTs are reduced.

[Austintatious]

10 hours ago, Shadrach said:

The TIT limits and the inherent  imbalances in the fuel/intake system are what cost you speed. Not your mixture setting. Most applications were not designed with an eye towards the precision needed for LOP operations. Mini turbo charged application is run fine on the lean side of peak. However, turbo normalized applications are better suited because their higher compression engines generate lower TITs. See two TN’d IO540s below making same horsepower at the same RPM. Manifold pressure and TIT is lower on ROP engine (L side) while CHTs and fuel burn are higher. Manifold pressure and TIT is higher on LOP engine (R engine) while fuel burn and CHTs are reduced.

Yea, sure, if you up the MP then run LOP to get the same power you are correct... but it simply cannot be done with my power plant.  The TIT will not allow it, perhaps because I am a TSIO and not TNed.  So the only way I can run LOP is at lower altitudes and the same MP/RPM I would run ROP, which means less power and thus slower flying... Believe me, If I could do this I would, I certainly love saving gas.

[Echo]

Andre,

 wish you would have posted this thread in vintage.  THAT would of kept the turbo talk away and kept the focus on the IO-360 Power plant.  When the carb guys and turbo guys chime in it just gets more confusing and I miss the nuggets and focus on the fools gold.  That said I always learn a bit when the thread wanders.   am looking forward to install of my EDM830 with fuel flow in February so I can confirm beyond the older multi probe one at a time CHT/EGT monitor I currently have.

Put me in the 65% down low and 70% power up high camp.  Scott

[Will.iam]

1 hour ago, Austintatious said:

Yea, sure, if you up the MP then run LOP to get the same power you are correct... but it simply cannot be done with my power plant.  The TIT will not allow it, perhaps because I am a TSIO and not TNed.  So the only way I can run LOP is at lower altitudes and the same MP/RPM I would run ROP, which means less power and thus slower flying... Believe me, If I could do this I would, I certainly love saving gas.

My TSIO-360 i run LOP up to 72% power is smooth as i push to 73% it starts to be not as smooth. Or to put it another way i can get to 70 degrees LOP. That’s my ceiling and I’m at .2 spread. When i was at .6 spread when i first got the airplane i could not run LOP either. If you can not figure out what is keeping you at .6 you will not be able to go very far LOP or at all at higher power settings. I also think my firewire tempest plugs and electronic surefly helps over come the .2 split i have right now. And honestly power drops off so quickly past 30 degrees LOP, it would only be worth it to me to refine the .2 spread if i wanted to push my LOP power past 72%. With my engine at TBO i will wait until after an overhaul before trying to refine it more. 

[Will.iam]

10 minutes ago, Echo said:

Andre,

 wish you would have posted this thread in vintage.  THAT would of kept the turbo talk away and kept the focus on the IO-360 Power plant.  When the carb guys and turbo guys chime in it just gets more confusing and I miss the nuggets and focus on the fools gold.  That said I always learn a bit when the thread wanders.   am looking forward to install of my EDM830 with fuel flow in February so I can confirm beyond the older multi probe one at a time CHT/EGT monitor I currently have.

Put me in the 65% down low and 70% power up high camp.  Scott

You have that backwards. Mother nature takes air away as you go higher. I. E. You can be 70% down low and 65% up high but keep going up you will be in the 55% or 45% camp. Hence the value of the turbo. 

[Huckster79]

On 12/30/2023 at 1:23 AM, Mooney in Oz said:

See page 2.

Bob Kromer.pdf 163.18 kB · 29 downloads

Thank you! Makes sense! 

[Shadrach]

16 minutes ago, Huckster79 said:

Thank you! Makes sense! 

That article is a good read. That being said, leaning to 100ROP  at 3000’ in the climb is too aggressive in my opinion. That’s well above 90% power.