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How to run lean of peak?


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Newbie question.  Supposedly running lean of peak is the way to go to get the most for your money.  For leaning I was taught to lean until the engine starts running rough, then enrichen the mixture until it smooths out again.  This is with a constant speed prop. 

 

1) Is this lean of peak, peak, or rich of peak? 

 

2) I have a CHT monitor, but haven't figured out how to use/read it yet.  Once I do, should I base running lean of peak off the leanest cylinder?  This would mean that only 1 cylinder would be running LOP while the others would still potentially be all over the place.  

 

3) If I run lean of peak using the CHT monitor, do I ignore the original way I was taught to lean?  So if lean til the leanest cylinder if 50 degrees lean of peak, do I ignore it if the engine is not running smoothly?

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My suggestion before you open this can do a search of this board there are plenty of threads on here that discuss LOP vs ROP and some get quite interesting.  Also do internet search for  Mike Busch "the savvy aviator" has some articles on this as well.

 

good luck and welcome aboard.

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Advanced Pilot Seminars!

Attend in person or do the online course. It's life changing and well worth the cost!

Check out http://www.advancedpilot.com

 

So you can spend your money learning about imaginary red box…I'll give you my advice, free of charge and it will keep your engine purring to TBO and beyond. Keep your CHTs below 400…Never ask a barber if you need a haircut. Never ask guys selling tuned injectors if running right at peak is bad for your engine...

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LOP uses less fuel, and gives less speed.

Right. Is, you are running Rich of Peak. Leaning is done using EGT, not CHT. Typically 20-30° LOP is sufficient, any more is either rough or too slow; 20° is a compromise between fuel savings and speed loss.

Pull mixture towards lean until EGT reaches a maximum value (remember which one reaches Peak last), then pull more until the last one to peak is 20-30° cooler than the peak. For more speed, lean until the first cylinder EGT reaches a maximum value, then push towards rich until 50° or more cooler than that peak.

John Deakin's "Pelicans Perch" articles make a great place to start. If you don't have an engine monitor that gives EGT values on each cylinder, then LOP can be risky. Be careful, study hard and see what happens.

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Newbie question.  Supposedly running lean of peak is the way to go to get the most for your money.  For leaning I was taught to lean until the engine starts running rough, then enrichen the mixture until it smooths out again.  This is with a constant speed prop. 

 

1) Is this lean of peak, peak, or rich of peak? 

Depending on har far you richen, you could be any of the three. If you Just richen a little (1/4 turn?) you should still be lean but it depends on where you were when the engine got rough. If not tuned injectors you might not be as lean at that point as you think. The one place you don't want to be is just rich of peak - according to the APS guys this is the absolute worst place to run your engine due to the combustion pressure cycle.

 

2) I have a CHT monitor, but haven't figured out how to use/read it yet.  Once I do, should I base running lean of peak off the leanest cylinder?  This would mean that only 1 cylinder would be running LOP while the others would still potentially be all over the place.  

As mentioned above, LOP is based on EGTs, not CHTs. If LOP you want to be lean of richest cylinder so you don't leave that cylinder just ROP, a bad place for it to be.

 

3) If I run lean of peak using the CHT monitor, do I ignore the original way I was taught to lean?  So if lean til the leanest cylinder if 50 degrees lean of peak, do I ignore it if the engine is not running smoothly?

You might need to do some work to get it running smoothly LOP. Try the GAMI lean test to see if your injectors are balanced. http://www.gami.com/gamijectors/leantest.php

Don't run so lean as to cause engine roughness. In my TSIO-360, I just can't go very lean, maybe 25deg LOP. But being able to find LOP and operate there safely is a necessary skill in my book - sometimes LOP is the best way to keep the engine cool, or to extend my range. Having said that, I tend to run ROP about 2/3 the time. I'd rather go faster, especially on westerly segments where I 'm bucking a headwind.

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Newbie question. Supposedly running lean of peak is the way to go to get the most for your money. For leaning I was taught to lean until the engine starts running rough, then enrichen the mixture until it smooths out again. This is with a constant speed prop.

1) Is this lean of peak, peak, or rich of peak?

2) I have a CHT monitor, but haven't figured out how to use/read it yet. Once I do, should I base running lean of peak off the leanest cylinder? This would mean that only 1 cylinder would be running LOP while the others would still potentially be all over the place.

3) If I run lean of peak using the CHT monitor, do I ignore the original way I was taught to lean? So if lean til the leanest cylinder if 50 degrees lean of peak, do I ignore it if the engine is not running smoothly?

1) I can't say without seeing the engine data. Knowing what I know about 4cyl injected Lycs, I'd bet you were 30-60LOP depending on altitude.

2) For ROP, use leanest cyl (all other cylinders will be safely richer). For LOP, use the richest cyl (all other cylinders will be safely leaner).

3) Your last question is not really something I can answer. What I can say is that you have some studying to do. ROP/LOP is not the point. Knowing how to optimize your operation to match your goal is. Read the articles linked below They were written by John Deakin, one of the instructors at APS. He does a great job of breaking down the fundamentals of combustion science and applying the information to aircraft engine operations...for free.

Pelican's Perch #66 Where Should I Run My Engine? (Part 1)

Pelican's Perch #66 Where Should I Run My Engine? (Part 2 -- The Climb)

Pelican's Perch #66 Where Should I Run My Engine? (Part 3 -- Cruise)

Pelican's Perch #66 Where Should I Run My Engine? (Part 4 -- Descent)

RE: APS, GAMI and the "Red Box"

You've gotten a lot of "free advice" in the above replies. Some of it is good, some of it is worth even less than you paid for it. There are references to APS and GAMI. I've never taken an APS class nor do I run injectors made by GAMI, but it's hard to deny the contributions these 2 companies have made to general aviation. For unknown reasons, some people like to bash them on various forums. As far as I know, the APS curriculum is in large part a graduate level discussion of combustion science that's been simplified and made more approachable, not a LOP instruction guide. I've met no one that has regretted taking the course.

As far as the "Red Box" (a dangerous area in the mixture curve that could lead to detonation) is concerned, the IO360 A1A in your E has extremely high detonation margins, and even the most ham fisted pilot would be hard pressed to induce detonation, much less damage the engine through mishandling. Almost any fool could run one of theses engines to TBO as long as oil is changed and its flown regularly. However, if you aspire to someday move into a machine with a more temperamental reciprocating engine and perhaps even a Turbo, the concept (and reality) of the red box becomes much more apparent as does the need to understand it. Learning the fundamentals now, will be of great benefit moving forward. Understanding combustion science is a useful tool not just for engine ops but for diagnosing engine problems in flight as well as on the ground.

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. . . and that it will run better there if you install their tuned injectors . . . [which are not needed by many Lycoming IO-360s]

GAMI has told many Lycoming owner's that the F/A distribution on their particular engine is optimal and that no modification is needed.
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Your airplane looks familiar. Is it the E with the rayjay turbo installed?

To put it in terms another pilot used when I asked about LOP, he said, "you're only burning 10gph to begin with"

Are you exempt from high altitude head winds? Or do you just suck it up and take the 10 to 40kt or more speed penalty. I often find myself running westbound at 1500'AGL (~2500MSL) to stay out of the winds. What's your burn down low?

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I would watch all the Savy Aviator (Mike Busch) vids and Pelican Perch (John Deakins) articles listed which cover it all pretty well. While they are certainly are proponents of LOP they also point out that you need ROP during takeoff which combines high power with poor cooling. I've seen advice that you insist that your mechanic set it a little RICHER that the published setting to give extra protection on takeoff; I think that implies that you'll be pretty active with the mixture control in all phases of flight and not just run it full rich all the time.

 

 In my experience I can get the same speed with lower fuel burn and lower CHT's using LOP up to the point where I hit the max power possible LOP.  Maximum power from our engines isn't even possible with LOP so if I really want to see how close I can get to my M20E's annoyingly low redline it'll be full throttle, maximum RPM, and 100 ROP ( and watch the CHT's like a hawk).  Since it often a little choppy where I fly I like to stay in the green and so am normally LOP in cruise.

 

My EI UBG-16 will do data dumps which I use a lot. I think it's better to do your deep thinking on the ground and just fly the plane when in the air. Once I had experimented with LOP at lower power settings where you can do little harm I basicly do a "big pull" from a given MP RPM setting and set the fuel flow (my favorites is 8 GPH for local and 10 GPH when on a trip which gets me closer to the yellow).

 

We have a lot of choices with respect to speed vs fuel efficiency and its worth the trouble to learn as much as you can and then put it to the test in the air.  You may be able to skip one fuel stop by going a little slower and save the time you would have been putzing around on the ground.

Many like it as simple as possible and some like it more complicated.

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I've seen advice that you insist that your mechanic set it a little RICHER that the published setting to give extra protection on takeoff; I think that implies that you'll be pretty active with the mixture control in all phases of flight and not just run it full rich all the time.

 

Maximum power from our engines isn't even possible with LOP 

 

 

Good post! The only thing I'd say is that FF on the Bendix RSA fuel system is not adjustable above idle (hat tip to Byron circa 2011) so the "have your mechanic set it rich" advice is only useful to Conti drivers.

 

I am also betting that up in your neck of the woods that -3000ft DAs are common place in the winter. I think it would be quite possible to pull 100% power LOP on a high pressure February morning running up the coast.  Admittedly a rare operating regime, but one of the best times to utilize LOP ops in an NA engine.

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Newbie question.  Supposedly running lean of peak is the way to go to get the most for your money.  For leaning I was taught to lean until the engine starts running rough, then enrichen the mixture until it smooths out again.  This is with a constant speed prop. 

 

1) Is this lean of peak, peak, or rich of peak? 

 

2) I have a CHT monitor, but haven't figured out how to use/read it yet.  Once I do, should I base running lean of peak off the leanest cylinder?  This would mean that only 1 cylinder would be running LOP while the others would still potentially be all over the place.  

 

3) If I run lean of peak using the CHT monitor, do I ignore the original way I was taught to lean?  So if lean til the leanest cylinder if 50 degrees lean of peak, do I ignore it if the engine is not running smoothly?

 

To answer your questions directly:

 

1.  You can't tell by whether the engine is running smoothly or roughtly whether or not you are LOP.  If the fuel distribution is pretty equal to all cylinders you are probably (but not positively) LOP.  If the distribution is not so even you may still be ROP.  The only way to tell is watch the EGT on all four cylinders as you lean.

 

2.  You are not LOP until the RICHEST cylinder is LOP.  Even if you don't learn how to use the "lean find" procedure you can still find LOP.  Just watch the EGT's.  As you lean, once all EGT's are decreasing you are LOP.  You'll find that one or two cylinders are usually the last ones to go LOP.  Once you figure out which ones, you can just watch them to see when they go LOP.

 

3.  No.  You want the engine to run smoothly.  If you can't get LOP before it runs roughly then you might want to invest in GAMI injectors for your engine.  If you can get LOP and still run smoothly, the most efficient setting is usually about 20 to 30F LOP.  Leaner than that and you start losing power and speed more than you gain in reduced fuel flow.  I usually end up setting the richest cylinder about 10F LOP while that leanest cylinder ends up being about 30-40F LOP.

 

Good luck,

 

Bob

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Good post! The only thing I'd say is that FF on the Bendix RSA fuel system is not adjustable above idle (hat tip to Byron circa 2011) so the "have your mechanic set it rich" advice is only useful to Conti drivers.

 

I am also betting that up in your neck of the woods that -3000ft DAs are common place in the winter. I think it would be quite possible to pull 100% power LOP on a high pressure February morning running up the coast.  Admittedly a rare operating regime, but one of the best times to utilize LOP ops in an NA engine.

 

I'd have to throw in a caveat though. On that same cold winter day with a low density altitude allowing you to generate 100% of rated HP LOP you could probably get 110%-120% ROP. 

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Newbie question.  Supposedly running lean of peak is the way to go to get the most for your money.  For leaning I was taught to lean until the engine starts running rough, then enrichen the mixture until it smooths out again.  This is with a constant speed prop. 

 

1) Is this lean of peak, peak, or rich of peak? 

 

2) I have a CHT monitor, but haven't figured out how to use/read it yet.  Once I do, should I base running lean of peak off the leanest cylinder?  This would mean that only 1 cylinder would be running LOP while the others would still potentially be all over the place.  

 

3) If I run lean of peak using the CHT monitor, do I ignore the original way I was taught to lean?  So if lean til the leanest cylinder if 50 degrees lean of peak, do I ignore it if the engine is not running smoothly?

 

I am going to have to bone you for opening this can of worms.

 

5-1-5†† for Inciting Aviation Personnel to Fury.

 

gig, get bagged, etc.

††5 demerits, grounded one week, 5 penalty tours.

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These threads to me are like a Ben Done movie...At least in another thread that half a dozen people enjoyed it was new material. I tune in to this when I wish to take a nap...Like an episode of Jeopardy in syndication the answers are the answers. The second...third...fourth...and 100th time viewed...or asked. Good for all you re-hashers...

Some people need to learn how to use a search function. This thread challenges the adage there is no such thing as a stupid question.

Oh, my bad. Welcome to MooneySpace. Are you a Space Cadet? Thought so.

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