Leaning LOP procedure

[MooneyBob]

Hi

I know it was discussed many times and sometimes it got out of control. We don't want that.

I just need short procedure confirmation if possible.

I have new CGR30P installed. It the manual for the LOP leaning (see below) it says to put it in the LOP mode. Pretty clear.

Pull the mixture and the monitor will find EGT peak of first cylinder and mark it. Pull the mixture more and it will put another markers on the cylinder as the EGT raises on them. Still pretty clear.

So I can see which cylinder is richest ( last to reach the peak).

But the numeric data provided is for first cylinder to reach the peak. Shouldn't I go by last ( richest) cylinder and then lean desired amount of degrees from this point? How do you lean LOP?

Please see copy of the manual article below. Thanks.

CGR30P Manual for LOP

Important Notice: The engine must be leaned and operated in accordance with the POH and engine manufactures recommendations. Information in this manual is for reference only and does not make any recommendations.

This operating mode was designed to assist the pilot in leaning

the engine Lean-of-Peak EGT. As you lean, the EGT bars for all

cylinders will rise. When the first cylinder reaches peak EGT a

tattletale marker will appear at the top of that cylinder’s bar. As

you continue to lean, additional tattletale markers will be placed

at the top of the appropriate bar as each cylinder reaches peak

EGT. This gives a quick visual reference as to which cylinders

have reached peak EGT and at what temperature each cylinder

peaked. If a false peak is detected (an EGT dips and then starts

increasing again), the CGR will reset the tattletale marker for that cylinder and once again look for the true peak.

The data provided in the top portion of the display will show the first cylinder to reach peak EGT and the current temperature below peak for that cylinder.

[Shadrach]

I have found that most instrument mfgs overcomplicate the process. I never use the "lean find" feature when leaning.  Find out which cylinder is leanest (first to peak) and use that for ROP power settings. Find out which cylinder is richest (last to peak) and use that for LOP power settings.  It's just that simple. The lean find feature on EI and JPI products is kind of a gimmick in my opinion. JPI even has a LOP lean find.  I could do without all of it.  

[Shadrach]

Since seeing this post, I have been researching the CGR30P.  Looks like a really nice piece. I would look forward to a pirep!

[midlifeflyer]

I have found that most instrument mfgs overcomplicate the process. I never use the "lean find" feature when leaning.  Find out which cylinder is leanest (first to peak) and use that for ROP power settings. Find out which cylinder is richest (last to peak) and use that for LOP power settings.  It's just that simple. The lean find feature on EI and JPI products is kind of a gimmick in my opinion. JPI even has a LOP lean find.  I could do without all of it.  

That's what the "lean assist" stuff is supposed to help with. Clearly some are more helpful than others. But  understanding the "assist" procedure requires understanding what you said. Great post.

[Cruiser]

Shouldn't I go by last ( richest) cylinder and then lean desired amount of degrees from this point? How do you lean LOP?

 

 

Bob, you are correct. Lean until the LAST cylinder goes peak and then measure the degrees LOP for that cylinder. Yes, that means the others will be leaner but you don't want to leave any cylinder too close to peak or slightly on the rich side of peak. That would be worse.

 

Of course leaning from the last to peak can make the leaner cylinders very lean (maybe more than you want) but only if there is a wide variation in peak caused by unequal fuel distribution or intake manifold (air) leaks to those cylinders. If that is so, treat it as a problem and have it fixed.

[MooneyBob]

Since seeing this post, I have been researching the CGR30P.  Looks like a really nice piece. I would look forward to a pirep!

Since seeing this post, I have been researching the CGR30P.  Looks like a really nice piece. I would look forward to a pirep!

Will do. So far I did only one short 2.5 hours flight to MQI. I really like it. It replaced bunch of old gauges, it is primary instrument, price is right, easy to set up and operate. It doesn't take a lot of space of the panel and it has very crispy display easy to read.

[Marauder]

Will do. So far I did only one short 2.5 hours flight to MQI. I really like it. It replaced bunch of old gauges, it is primary instrument, price is right, easy to set up and operate. It doesn't take a lot of space of the panel and it has very crispy display easy to read.

I didn't know your J is a '77.

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[MooneyBob]

I didn't know your J is a '77.

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I hope it is not too bad news. I like it so don't ruin it for me.

[Shadrach]

That's what the "lean assist" stuff is supposed to help with. Clearly some are more helpful than others. But understanding the "assist" procedure requires understanding what you said. Great post.

True, but why not just lean slowly and watch. I mean if one has an understanding of how to use the "lean find" then one doesn't really need to use the "lean find"... It would have been the perfect feature for Capt. John Yossarian.

[Marauder]

I hope it is not too bad news. I like it so don't ruin it for me.

Not at all, thought for some reason you owned a late 70s version... The quadrant gave it away.

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[Hank]

Not at all, thought for some reason you owned a late 70s version... The quadrant gave it away.

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What, 1977 isn't "late 70s"???--says the 1970 model flier . . .

Besides, quadrants are cool.

[Tommy]

Pretty easy

 

1) do the big pull to avoid staying in the red box for too long

2) activate "lean" lean find

3) slowly lean the mixture until the last cylinder's EGT peaks - your engine monitor should tell you when this happens as well as the actual EGT reading

4) then further lean another 50 to 100 degree using that cylinder's EGT 

 

All this time, watch the CHTs. If you lean too slow, the CHT may rise. So be careful!

[Shadrach]

Pretty easy

 

1) do the big pull to avoid staying in the red box for too long

2) activate "lean" lean find

3) slowly lean the mixture until the last cylinder's EGT peaks - your engine monitor should tell you when this happens as well as the actual EGT reading

4) then further lean another 50 to 100 degree using that cylinder's EGT 

 

All this time, watch the CHTs. If you lean too slow, the CHT may rise. So be careful!

If "the big pull" is performed, the engine is already LOP, further leaning (as your intructions suggest) will not produce peak on any cylinder, one would have to enrichen. To use lean find one would have to select the proper lean find mode (lop mode) first and then enrichen. Howevere, his instrument has a very readable graph of EGTs with the numbers underneith. Instead of using lean "lean find" why not do the following?

1) Climb to a suitable cruise altitude (5500-8500 is fine).

2) Lean until one cylinder peaks. Note the cylinder and take a little time tweeking it to find absolute peak EGT (if you use lean find this may confuse it) and note fuel flow. This is the leanest cylinder and is used for ROP operations.

3) Continue leaning deliberately but slowly throught the peaks of the rest of the cylinders until you find the last to peak. Note the cylinder and tweek it to find absolute peak. Note fuel flow. This is the richest cylinder and is used for LOP operations.

The diff in fuel flow between the first and last is the GAMI spread. Which ideally is <.2gph.

If electing to use lean find, The procedure will have to be performed twice. Once from ROP until the first cylinder peaks and once from LOP until the first cylinder peaks.

Regarding the "big pull". All of us learned to LOP one way or another from those wonderful gents at GAMI/APS. However, I beleive the "big pull" is a CYA procedure on most aircraft and is really only crucial in GTSIO, TSIO and TIO engines. It's likely no needed on an IO engine unless you're leaning at 1500msl, and even then it's unlikely to hurt anything. Think back to your primary training flying carbed 160 and 180hp machines. Dollars to donuts no one ever tought you to pull the mixture, above 3k its ok to just twist until rough and enrichen to smooth. While it is possible to abuse an IO360 with power settings, getting a properly set up engine to over temp or detonate in level flight is downright difficult if not impossible. So just don't do your lean test at low altitude while climbing at Vx or Vy with gear down, cowl flaps closed and your engine should be just fine.

[slowflyin]

I'm a big pull user. Not because it's safer but because I find using fuel flow much more efficient, I pull to around 8.5 to 9 GPH and let the CHTs settle. If over 350 I pull some more. If under 350 (normally they are 310 -325) I push until the hottest is under 350. Simple procedure with consistent results. I fly lots of weather, unfamiliar airports and air space so being able to pull for literally less than to seconds gets me back in the aviate, navigate, communicate game much quicker. Four or five minutes later, or as work load allows, I take another two seconds to fine tune. I've flow both the JPI and CGR and it seemed I needed to start well ROP and lean slowly, at a consistent rate for the units to work properly. In the end I noticed the FF was always about the same.

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[Shadrach]

I can do the same thing with airspeed and or deceleration. If you really want to know which cylinder to watch for ROP/LOP situation you have to watch the numbers at least once.

All this talk of CHTS has gotten to me. I had a dream last night that I fried a jug flying at low level in the high plains (I don't even live near the that kind of climate). I put it down in snow and straw but it bent everything. It was more of a nightmare actually.

[Tommy]

Big pull is not about detonation avoidance rather it's to avoid high intra-cylinder pressure, which increases steadily and peak at ROP 50F, which coincides with high CHTs.

 

Sorry I didn't make it clear. A big pull to rough then enrich with two full rotations to get to ROP of approximately 50 to 100ROP, activate lean find "LOP," then start turning the mixture knob slowly, watch EGT start to rise. In EDM 700, the graph change as soon as the first cylinder peaks to "LOP" display.

 

Now it's generally not advisable to stay in 50F ROP especially if your power setting is above 75%. This will put you right in the red box - a big no no to the engine health. But if you set your power at 65%, then you can do whatever you like without hurting the engine until CHT gets too hot (takes minutes).

[dtoelke]

I'm sure this has been posted around before, but it's a great article for those who are new to LOP ops.  This is the way I lean.  Once you run the plane LOP a couple times it's pretty easy to get within the ballpark after a quick mixture pull and throttle adjustment.

 

http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning-198162-1.html

[doubbrunn]

I am new to Mooneyspace, but have been flying an IO-550 LOP for many years.

 

I strongly recommend the Advanced Pilots Seminar given by GAMI/Tornado Alley Turbos.  Lots of good information - not just LOP

 

Just one comment about finding peak - you don't have to find it from the rich side!

 

If you find peak from the lean side, you will not spend nearly as much time in the red box.

[PTK]

I have found that most instrument mfgs overcomplicate the process. I never use the "lean find" feature when leaning.  Find out which cylinder is leanest (first to peak) and use that for ROP power settings. Find out which cylinder is richest (last to peak) and use that for LOP power settings.  It's just that simple. The lean find feature on EI and JPI products is kind of a gimmick in my opinion. JPI even has a LOP lean find.  I could do without all of it.  

 

Very well said Ross. With your permission, may I add only one thing.

 

Do a mixture distribution test and determine your GAMI spread first. This will show you your richest cylinder and will tell you if your leanest cylinder could potentially end up being too lean.

[gsxrpilot]

This document is an excellent resource for getting to know LOP. Go fly and follow this procedure. It will help you learn where your plane is LOP and get comfortable with it. After doing it this way a few times, you'll know where to pull the mixture and can do it in a matter of seconds.

The main suggestion I'd make is to be high enough altitude so that you're at only about 65% power. At that low power setting, you can't do any damage to the engine no matter how slowly you move the mixture in and out. 

SavvyAnalysisFlightTestProfiles.pdf

[carusoam]

Two fun things to do with all that Gami injectors that you installed...

See how far LOP you can go, before the engine shuts down...

At 5k’ my IO550 could go about 90°F LOP before it got quiet...

At about 10k’, only about 50°F LOP.....

I’m not sure what to expect with a well balance IO360

For cruise settings... 65%, and below, and just a few °F LOP... to maximize fuel efficiency, and max power, keep an eye on CHTs to make sure everything is happy...  my theory on converting as much fuel to speed as possible...

No fuel gets used for cooling... no excess air gets compressed... 

PP thoughts only, not a CFI...

Best regards,

-a-

[PT20J]

To understand the big pull and red box, it might be helpful to review their origins.

If you lean according to Lycoming and Continental recommendations, that is set power to 65% to 75% (depends on the engine and installation) and then adjust mixture, you can set it anywhere you like without hurting anything. There isn't really a red box that you need to worry about. (Yes, I know  maximum pressure and CHT occurs at 50F ROP. As long as CHTs are 400F or less - or maybe a little higher -  you will still be well within the design limits of the engine). This worked great when everyone was running ROP, because leaning doesn't affect the power more than a few percent when ROP.

But, when you get LOP, the power drops off rapidly with decreasing mixture strength. If you start at 75% power on the rich side and then lean to well LOP,  the engine will be producing much less than 75% power. The fuel flow is impressively low, but the airplane slows way down. You can't sell a lot of injectors if they turn your Bonanza into a Cherokee. The solution is to increase MAP and perhaps RPM to get the power back to 75%.

This procedure is a bit cumbersome: 1) Set power ROP to 65-75%. 2) Lean to LOP. 3) Reset power. The engine is most efficient at WOT. Why not leave the throttle full open and just pull the mixture back to LOP (big pull) to get the power you want and be done with it? If you do this in a turbo, or at low altitudes in a NA engine, there most definitely is a red box that you want to avoid and the big pull neatly avoids dwelling there.

Skip

 

[Tommy]

I have since changed my LOP procedure because these days I almost always fly at 7000 and above so red box is no longer relevant even at WOT / 2350. So I just slowly lean back without the big pull. 

[EricJ]

The Lycoming approved procedure is to lean to roughness (for carbureted) or loss of airspeed (or power, essentially, for fuel-injected), then enrichen a little for smooth operation.

That will put it in LOP operation.   If you do this and just monitor CHT/EGT to make sure you're not doing anything dumb for your particular motor, it's a pretty good procedure.

 

[midlifeflyer]

55 minutes ago, EricJ said:

The Lycoming approved procedure is to lean to roughness (for carbureted) or loss of airspeed (or power, essentially, for fuel-injected), then enrichen a little for smooth operation.

That will put it in LOP operation.   If you do this and just monitor CHT/EGT to make sure you're not doing anything dumb for your particular motor, it's a pretty good procedure.

 

It's kind of funny with all the arguments about LOP operations that this standard leaning method taught in Cessna 152s, 172s, Cherokees, and just about all other primary trainers without an EGT gauge results in LOP operations.