Quick leaning opinion - NOT LOP vs. ROP

[carusoam]

On 4/21/2020 at 4:32 AM, FastTex said:

I have been following one of the recommendation on this forum to work best for my engine (360-A1A with a JPI830):

8.5GPH LOP

12.5GPH ROP

NEVER 10GPH

 

let’s start with what ‘works best’ means...
 

Without the context of where this comes from...  that one recommendation...

This statement is just missing the details needed to be safe.

it basically says...

1) I fly sooo ROP I can’t get anywhere near the red box... it costs me a ton of excess fuel...

2) unless I am LOP... where I avoid the red box by a giant margin... it costs me a ton of speed...

3) I don’t go anywhere near peak which is assumed to be 10gph... but I don’t know for sure...

4) Since I don’t mention MP or altitude... or RPM I might be operating at edge of the red box ... without even knowing it...

5) Since no two Mooneys are perfectly alike... using a direct relationship copied from a similar plane without testing it... is ripe with hazard...  in a similar way... we know where the stall speed should be... but don’t use it until we safely go to altitude and prove everything is working as expected first...

6) Everything changes with the weather as well...

It doesn’t follow the leaning practice of identifying peak for the MP and rpm you are using...

Something is getting lost or left out...

Want  to describe your ideal flight to experiment with?

We can discuss °F LOP/ROP... and the resulting FF...

Our planes were not built with the single knob theory in mind... where we set a FF and know what happens next...  

our raw EGt numbers are equally confusing for a few reasons... that is why we use Peak! Not something like 1355°F

 

the reason we have the extra instruments is to allow greater speed and greater efficiency, while the safety we get is for the engine...

@12.5gph... My O cruises along at 160kts...  10° LOP, WOT, 2500rpm at 10k’...

by bumping up the rpm to 2550, the FF increases to be at the same °F LOP...

You can do better than that with an IO360! 
 

Lets get started..!

Best regards,

-a-

 

[Shadrach]

I took for granted that the prework for the subject was completed.

At a minimum, that would include:

Knowing richest cylinder (last to peak)

Knowing leanest cylinder (first to peak)

Verify that the engine runs smoothly throughout the mixture spectrum (ignition, intake and fuel system in good running order)

The use of the mixture control should be slow but deliberate. Pause and wait when fine tuning.

 

I think Anthony @carusoam is clarifying my comments on leaning to slight roughness. To clarify further, the process I mentioned feels very much like leaning a rental 172 - lean until rough enrichen just enough until smooth. However, it is different in few ways.  A typical IO360 will be at a very different mixture setting as it approaches roughness when compared to an O360. The carbureted engines typically get rough as the richest cylinder approaches peak EGT (+/- a few degrees). The injected engine in proper tune (no intake leaks, ignition or fuel delivery) will not get rough until the richest cylinder is well past peak EGT. How far past peak EGT will depend on  GAMI spread and how much manifold pressure is available.  Leaning an IO360 to rough and enrichening until smooth will typically leave the engine at a much leaner than optimal mixture setting.  This is because most IO360s will run smoothly at settings much leaner than optimal. O360s do not share this trait because carburetors do not distribute fuel to each cylinders as evenly. As an O360 approaches peak the differences in power being produced by each cylinder become more evident in the form of engine roughness.

Rather than turn this into a white paper on leaning it’s probably best to just send you to the guy who has written most extensively on the subject. I enjoy John Deakin’s work on a host of subjects, but his writings on engine operation have truly changed how GA pilots understand and operate their machines. The columns are concise, easy to understand and not overly long.

Where should I run my engine (part 1)

Where should I run my engine (part 2)

Where should I run my engine (part 3)

Where should I run my engine (part 4)  
 

He’s written a great deal more than what I’ve linked here. You asked for something quick which is what I put in my post online. However, Like most things,  you probably shouldn’t be doing it quick until you understand what you’re doing.

Edited May 6, 2020 by Shadrach

[gsxrpilot]

I can relate to the OP here. When I first became the one and only responsible for the health and longevity of an airplane engine, I thought the same. "Just give me the quick instructions." "I don't need all the theory right now, just tell me how." 

As you might expect, it never worked quite right and I really couldn't understand or experience, the huge differences everyone was talking about.

Then I went to Ada, OK and spent an entire weekend in a classroom setting, studying ROP/LOP and all things engine management. Wow! Now it's clear as day. And with heaps of data to back up the knowledge. 

I'm sure there are plenty much quicker than I who don't have to invest a whole weekend in Oklahoma to understand this stuff. But there's no question that in light of the investment I have in both safety and dollars, hanging on the front of my Mooney, that weekend in Ada was the best money and time I've spent since becoming an owner.

[Prior owner]

That was a great read, Ross. Thanks for posting the links. While this has probably been beat to death in other threads, The Lycoming Operators Manual for the 360 series states:
 

LEANING TO EXHAUST GAS TEMPERATURE GAGE.
a. Normally aspirated engines with fuel injectors or uncompensated carburetors.
(1) Maximum Power Cruise (approximately 75% power) – Never lean beyond 150°F on rich side of peak EGT unless aircraft operators manual shows otherwise. Monitor cylinder head temperatures.
(2) Best Economy Cruise (approximately 75% power and below) – Operate at peak EGT.

.....Lycoming’s  “Economy Cruise“ puts you deep inside the Red Box. My 1964 M20D operating manual is silent in regards to leaning procedures, other than the provided charts for “Best Power Mixture”. 
 

The older Mooney POH’s leave a lot to be desired..

[Shadrach]

8 minutes ago, PilotCoyote said:

That was a great read, Ross. Thanks for posting the links. While this has probably been beat to death in other threads, The Lycoming Operators Manual for the 360 series states:
 

LEANING TO EXHAUST GAS TEMPERATURE GAGE.
a. Normally aspirated engines with fuel injectors or uncompensated carburetors.
(1) Maximum Power Cruise (approximately 75% power) – Never lean beyond 150°F on rich side of peak EGT unless aircraft operators manual shows otherwise. Monitor cylinder head temperatures.
(2) Best Economy Cruise (approximately 75% power and below) – Operate at peak EGT.

.....Lycoming’s  “Economy Cruise“ puts you deep inside the Red Box. My 1964 M20D operating manual is silent in regards to leaning procedures, other than the provided charts for “Best Power Mixture”. 
 

The older Mooney POH’s leave a lot to be desired..

Glad you enjoyed those articles.  Deakin does a great job of simplifying the concepts. The red box is theoretical and varies from engine model to engine model. I have done a lot of experimenting with the angle valve IO360.  I do not advocate operating one's engine in an aggressive manner, but will say the following:

The IO360's operational red box is somewhat smaller than most of the graphics on the web. How much smaller I cannot say. Let's just call it a fuzzy red box...  All other things being equal, my engine typically runs cooler at peak EGT than 100ROP.

Deep LOP is not needed for most operations. 25LOP or less is sufficient for healthy CHTs even in warm weather depending on power setting.

CHT start to drop right after 50ROP EGT a trend that contiues until the engine starves for fuel.

The IO360 is very, very resistant to detonation.  It would require a large degree of inattention or deliberate abuse to make the engine detonate. Most of us operating with sub 400CHTs are being pretty conservative with our cylinders.  They will take more but why heat them up if it is not necessary.

My MO is to run as close to peak on the lean side as temps will permit.  This ensures I am making the most power possible at the best BSFC.  I do run ROP but I reserve that for high altitude, climb and unique situations where I absolutely must go as fast as possible.

 

 

[FastTex]

Just to close the loop...thanks @Shadrach for posting John Deakin's links. I read them a few years ago but after reading them again I understand more. And I will need to read them a few more times ;-)

In case anyone is interested I have put together a shorter and consolidated version of the articles in a kneeboard format. I have not changed the wording but just trimmed to what I believe is the essential. Nice to have it handy with me. Please post any feedback in here so I can keep learning!

Thanks All.

Enjoy.

Engine Management - kneeb - AA.docx