LEAN OF PEAK QUESTION

[FAST FLIGHT OPTIONS LLC]

All-

Quick LOP question as I recently upgraded to an M20K (from my J) and seem to have the ability to run LOP on the stock injectors.  I was following the POH for Best Economy 65% power (28"/2500 RPM) however; the book calls for peak TIT (not to exceed 1650 degrees F) once I lean to peak which was about 1600 today and is where the POH says i should have stopped i kept leaning to 1550 (50 LOP) engine ran great (no shaking) and I was buring a mear 9 GPH.  I pushed the throttle foward to get back the 2 inches of MP I lost when I went LOP and life seemed to be good.  Temps were normal and i was saving money.  Am i missing anything with this or is that about it? Seems to be alot of discussion about what seems to be a fairly simple procedure. Just want to make sure I'm not hurting my engine by doing what I'm doing

Thanks

[GeorgePerry]

Lots of mixed emotions on LOP.  I'm a fan of LOP but others aren't.  Link to a good article by Bob Kromer on cruise power settings.  I've had positive experiences with GAMI's / LOP in turbo Mooneys but you might want to talk with the expert (George Braly) at GAMI before giviing it a try

http://www.mooneypilots.com/mapalog/cruisepower.html

[KLRDMD]

Quote: 201-FLYER

I kept leaning to 1550 (50 LOP) engine ran great (no shaking) and I was buring a mear 9 GPH.  I pushed the throttle foward to get back the 2 inches of MP I lost when I went LOP and life seemed to be good.  Temps were normal and i was saving money.  Am i missing anything with this or is that about it? Seems to be alot of discussion about what seems to be a fairly simple procedure. 

[mooney231]

In the K I fly, below 10,000 ft. we cruise at 31"/2400RPM and I normally lean by TIT and fuel flow for fine tune adjustments with stock injectors.  1550ºF TIT is where I like to lean to (50º LOP) at about 9.5 - 10 GPH.  At the higher altitudes, a little more fuel is required to keep the engine running smoothly (11 GPH), but I usually set the power above 10,000 ft. according to the POH numbers printed on the pilot's side sun visor.

I find TCM engines have injectors that are balanced such that they allow for a more smooth and easy LOP operation.  I haven't had the same observation with Lycoming engines, but perhaps that's just my own personal experience.  Ken's comments about some of the LOP benefits are spot on... lower CHTs, internal pressures, less oil consumed, etc.

[GeorgePerry]

another good article on LOP

http://www.avweb.com/news/reviews/182501-1.html

[FAST FLIGHT OPTIONS LLC]

Quote: GeorgePerry

Lots of mixed emotions on LOP.  I'm a fan of LOP but others aren't.  Link to a good article by Bob Kromer on cruise power settings.  I've had positive experiences with GAMI's / LOP in turbo Mooneys but you might want to talk with the expert (George Braly) at GAMI before giviing it a try

http://www.mooneypilots.com/mapalog/cruisepower.html

[GeorgePerry]

Quote: 201-FLYER

-Nick

[danb35]

Quote: 201-FLYER

I find it intresting the author of the article advocates 50 degrees ROP.  Many on this forum indicate that's the worst place for an engine to be for some reason.  In any event it was good and informative reading. Thanks

[jlunseth]

I am not going to chime in on the LOP v. ROP argument.  I have been to the GAMI Advanced Pilot Seminar and have seen an engine run on their stand.  Notwithstanding, I do not run LOP in my M20K 231 at this time.  Why?  Because the performance among the six cylinders is too big right now.  I am going to try to get it tuned more optimally this winter, but by nature the M20K 231 does not have a tuned induction system.  I have the Gami injectors, but they only partially solve the problem.  My experience is that my engine seems to be tuned for a particular HP setting, somewhere around 65% (the cylinders will all peak at about the same time), but not at higher power settings.  At 75% I have a fairly wide variation among the cylinders in terms of when they peak.

I am writing to say I hope you have an engine analyzer that reads each of the six cylinders, and that when you say you are 50 LOP you are talking about the richest cylinder (last to peak) being 50 LOP.  If you are running with a one gauge set up, reading just the factory EGT and leaning from that, you could really be hurting your engine.  Well, maybe not at 60% power, but then again maybe.  The reason has nothing to do with the ROP/LOP debate and which side of it you want to be on.  It has to do with the fact that if there is too much variability among the cylinders in terms of when they peak, you could be running some cylinders LOP and some right in the "red box," where you do not want to be. 

GAMI's recommendation for degrees LOP in a turbo engine is basically 60-125 dF LOP.  But they also make it very clear that you have to consider your engine as basically six separate engines, each one running at a different setting LOP or ROP, and you have to make sure that all six of them are in a safe zone. 

[M016576]

It seems like this question comes up about every 2-3 months, and everyone has a different opinion on how to do it...

I normally fly between 8k and 11k in my 201.. at those altitudes, with a WOT and 2500 RPM, I'm normally making between 60-65% HP.  So.... I normally fly at PEAK EGT.  If I go LOP, I'm losing horsepower.  If I go ROP, I lose fuel.  At peak, below 65% HP, I'm seeing CHT's in the 310-330 region and I know that my ICP's aren't extreme enough to hurt anything. 

Below 8K, I run about 25 degrees LOP.  But I normally don't cruise at 3K or below (When I'm that low, I've already richened up the mix significantly for landing, or I'm full rich (or close to it) for T/O).   

Like most of the articles mention: stay out of the red zone and you're pretty much free to handle your situation however you deem best.

 

-JoB

[FAST FLIGHT OPTIONS LLC]

Quote: jlunseth

I am not going to chime in on the LOP v. ROP argument.  I have been to the GAMI Advanced Pilot Seminar and have seen an engine run on their stand.  Notwithstanding, I do not run LOP in my M20K 231 at this time.  Why?  Because the performance among the six cylinders is too big right now.  I am going to try to get it tuned more optimally this winter, but by nature the M20K 231 does not have a tuned induction system.  I have the Gami injectors, but they only partially solve the problem.  My experience is that my engine seems to be tuned for a particular HP setting, somewhere around 65% (the cylinders will all peak at about the same time), but not at higher power settings.  At 75% I have a fairly wide variation among the cylinders in terms of when they peak.

I am writing to say I hope you have an engine analyzer that reads each of the six cylinders, and that when you say you are 50 LOP you are talking about the richest cylinder (last to peak) being 50 LOP.  If you are running with a one gauge set up, reading just the factory EGT and leaning from that, you could really be hurting your engine.  Well, maybe not at 60% power, but then again maybe.  The reason has nothing to do with the ROP/LOP debate and which side of it you want to be on.  It has to do with the fact that if there is too much variability among the cylinders in terms of when they peak, you could be running some cylinders LOP and some right in the "red box," where you do not want to be. 

GAMI's recommendation for degrees LOP in a turbo engine is basically 60-125 dF LOP.  But they also make it very clear that you have to consider your engine as basically six separate engines, each one running at a different setting LOP or ROP, and you have to make sure that all six of them are in a safe zone. 

[jlunseth]

Yes, you are right according to the GAMI people.  As a general rule, you can fly at any mixture setting you want below 65% according to them.  Yes, peak TIT at 75% is not very good for your engine. 

The engine I watched run on their stand during the seminar was not a TSIO-360, and actually I don't remember what it was.  But I do remember that there was some detonation at that power setting (peak TIT and high power) on that engine, and the pressure spike was quite noticeable.  Made me uncomfortable watching it. 

[Ragsf15e]

Quick question about EGTs when running LOP... my GAMI spread is between 0.2 ~ 0.5 and I usually fly around 65% power and just barely LOP.  Recently I've noticed #4 (which is always last to peak) also decreases slower (noticeably) than the other 3 EGTs once I'm LOP.  This causes me to get ~50 LOP on 3 cylinders and maybe 5 LOP on #4 even with the small GAMI spread.  It's easy to get too lean on 1, 2, or 3 and cause it to sputter a bit before I get #4 comfortably LOP.

Any ideas on what I can do to remedy this?

[jaylw314]

22 minutes ago, Ragsf15e said:

Quick question about EGTs when running LOP... my GAMI spread is between 0.2 ~ 0.5 and I usually fly around 65% power and just barely LOP.  Recently I've noticed #4 (which is always last to peak) also decreases slower (noticeably) than the other 3 EGTs once I'm LOP.  This causes me to get ~50 LOP on 3 cylinders and maybe 5 LOP on #4 even with the small GAMI spread.  It's easy to get too lean on 1, 2, or 3 and cause it to sputter a bit before I get #4 comfortably LOP.

Any ideas on what I can do to remedy this?

Holy old thread bumping, Batman!

I also have a similar effect on the #4 cylinder.  IMO, some of it might be from the way the induction system works, but some of it might be from weak spark.  As you lean, the mixture gets harder to fire, and if one of your plugs fails to ignite, the EGT looks like a mag check (higher EGT), making it look like you have a double-peak.   If it happens intermittently, it can end up looking like one spread-out peak.

When I switched my left-mag spark plugs to fine-wires, it seemed to improve this problem, and I now get a more well-defined peak on #4. Later, I found out my left mag needed it's e-gap timing redone, so that would seem to match.

Upshot is, try fine-wire plugs on that cylinder.  If not, bench-checking your magnetos.

[kortopates]

Quick question about EGTs when running LOP... my GAMI spread is between 0.2 ~ 0.5 and I usually fly around 65% power and just barely LOP.  Recently I've noticed #4 (which is always last to peak) also decreases slower (noticeably) than the other 3 EGTs once I'm LOP.  This causes me to get ~50 LOP on 3 cylinders and maybe 5 LOP on #4 even with the small GAMI spread.  It's easy to get too lean on 1, 2, or 3 and cause it to sputter a bit before I get #4 comfortably LOP.
Any ideas on what I can do to remedy this?

It's normal and perhaps more an indication that your true gami spread is closer to .5 than .2 i.e. the larger the spread the more easily this happens. But as long as your not getting premature missing its okay. Any missing at 50 LOP or less is premature which of course is an independent issue.

Make sure your spreads are as accurate as possible by ensuring your monitor is sampling at its fastest rate or at 1 Hz and that you change mixture very slowly. Also do the test at a WOT Power setting, not more than 65%, so that MAP isn't changing nor being influenced by induction leaks. Doing it slowly with monotonically decreasing or increasing FF is critical to capturing good data.


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[Cruiser]

Yes, I would suspect you are leaning too quickly. 

When you stop leaning the induction system needs to stabilize. The air distribution continues to change which you see as further leaning of the first three cylinders using up more of it. As the first three cylinders gulp air there is less and less available to the last cylinder so you can continue to lean but it doesn't show any change. 

Your true balance is much worse than the initial indication. I would start by double checking all the connections/gaskets on the intakes.

[gsxrpilot]

I find it works best when I "pre-lean".

I'll set 65% power and lean to between 100 and 75 degrees ROP. I'll let everything settle down and stabilize and then make the big pull to the LOP side. 

You'll also want to make sure you have a nice hot spark. I thought everything was perfect but was still struggling to get all cylinders over the line together. Then I had a mag issue and we pulled the left mag for inspection. It was corroded beyond belief. And we were surprised that any of the left mag plugs were firing. They were, but very weak. A new mag, strong spark and LOP is now easy.

[ArtVandelay]

I find it works best when I "pre-lean".
I'll set 65% power and lean to between 100 and 75 degrees ROP. I'll let everything settle down and stabilize and then make the big pull to the LOP side. 
You'll also want to make sure you have a nice hot spark. I thought everything was perfect but was still struggling to get all cylinders over the line together. Then I had a mag issue and we pulled the left mag for inspection. It was corroded beyond belief. And we were surprised that any of the left mag plugs were firing. They were, but very weak. A new mag, strong spark and LOP is now easy.

I would think an in flight mag check would have identified this problem?

[gsxrpilot]

36 minutes ago, teejayevans said:

I would think an in flight mag check would have identified this problem?

Yes it should.  I'm certainly a believer in the in flight mag check and practice it pretty regularly. 

What I saw during the mag checks was both working, with one mag causing a little bit more of an EGT rise than the other.  I came up with all kinds of excuses for this. I just didn't recognize that one of the mags was extremely weak and failing. 

[Ragsf15e]

Awesome, thanks for the help and ideas.  I’ll put my jpg on 1” interval and lean really slow.  I already use target get in the climb, so I usually arrive at level off around 100 ROP.

Yeah, I hated to bump a thread that old, but I really didn’t want to start another LOP leaning thread!

[gsxrpilot]

Go to SavvyAnalysis and download the Test Flight Profile... Then go fly it and report back.

Here's the link.  http://content.savvyanalysis.com/static/pdf/SavvyAnalysisFlightTestProfiles.pdf