How do I run lean of peak?

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rookie1255

Pre-takeoff checklist
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rookie1255
First off, I would like to avoid the discussion of whether running LOP is acceptable. That is for a zillion other threads out there. Assume it's ok. My question is, how does one run LOP? I was taught to lean until the engine starts sounding rough, and then to turn in the mixture knob a little until the roughness stops. Is this always running LOP?

I would think it must be since any leaner and the engine doesn't sound happy. If this method works then it'd be easy to maintain running LOP. If engine sounds rougher from climbing then just enrichen til roughness stops. If descending then lean until engine rough and redial it in.

I know one could also look at the engine monitor and lean slowly until the peak is seen, and then keep leaning until 50 degrees drop from peak. This seems like it'd take longer, would have the engine spending more time in the "peak" temperature range, and would be more complicated to manage (more time staring at engine monitor than looking outside.)

So to sum it up, does pulling mixture til roughness automatically work for LOP, or could I accidentally be running ROP?
 
What are you flying? Carbureted or fuel injected? Do you have an engine monitor?

If you lean to roughness then richen a bit, that's as lean as you're going to run. If you're LOP, great. If not, you're going to need GAMInjectors to run any leaner. If you're carbureted, just forget about it.


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Fuel injected and there is an engine monitor. The engine is a Lycoming IO-540 C4B5. I did a little more reading and it's getting more complicated. I guess a GAMI lean test would be in order, then maybe buy expensive GAMI injectors, spend time tuning them, etc. I guess for now the pull til roughness should work and if I want to take it further for maximum efficiency it would be a lot more work and money.
 
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rookie1255 said:
Fuel injected and there is an engine monitor. The engine is a Lycoming IO-540 C4B5. I did a little more reading and it's getting more complicated. I guess a GAMI lean test would be in order, then maybe buy expensive GAMI injectors, spend time tuning them, etc. I guess for now the pull til roughness should work and if I want to take it further for maximum efficiency it would be a lot more work and money.
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I was being facetious in my last post. With a lycomingthere probably isn't a need for gamis. Go up and see where each cylinder peaks. If they're all close ( not in temp, in mixture setting ) then you're golden. Just lean it until they all peak and keep going until,you get it where you want. At a minimum you need an egt on each cylinder.
 
One thing to consider is to reduce power to 65% or less before experimenting with LOP operation. At or below 65% power you can't hurt the engine with the mixture knob. After you learn about how the engine behaves you can move on to leaning at higher power settings/higher manifold pressures.
 
Go with the Gami's ,follow the instructions and you can fly true lean of peak every time.
 
Do you have a good fuel flow meter? Running LOP is limiting the amount of fuel. Once you get it running -50°, note the fuel flow in GPH or lbs/minute or whatever.
Next time you go LOP, simply pull the mixture control until the fuel flow is where you want it and then check your EGTs to confirm that it is the LOP setting you want. Tweak the mixture control as needed. It's pretty fast, straightforward and doesn't keep you long in the hot zone while you're turning the vernier. To me, it was one steady pull. After you do it a few times your ear will help you know when you're getting close, so you can do this without initially looking at gauges until you fine tune the setting. Takes a couple of seconds.
If you run a little too lean or even too rich for a few seconds your engine will not explode. Don't let it sit in an inappropriate range, but a few seconds is not going to kill it.
 
If you are running that engine until it stumbles and backing off a bit, you are most likely LOP. I run LOP and I get there before the engine hiccups.
 
If it's fixed pitch, it will lose RPM on the lean side well before it stumbles. Stumbling means one or more cylinders is so lean that is incombustible.

For a car, I'll tune mixture with a vacuum gauge, so it ought to be possible with an MP gauge. Though I've never seen a POH describe that.
 
 
Read them all. Reading and nodding my head up and down is one thing, going up and then figuring out what I'm doing in flight is always different. So say I do the big mixture pull and all my cylinders are LOP and outside the "red box." Then I enrichen until the 1st cylinder peaks. Then I want to lean again to get that cylinder away from peak.

So I should shoot for 20-30 degrees LOP for THAT cylinder then, and that 20-30 degrees is 20-30 degrees based on the exhaust gas temperatures. Cylinder head temperatures should automatically be under 400 since I'm 20-30 degrees LOP. If cylinder head temperature for that one cylinder is at or close to 400, then I should keep leaning to bring the temperature down. Does that sound pretty good?

I'm looking for a procedure that can be condensed and used in flight that I can also understand. The articles about the mixture knob in different phases of flight is pretty good, but still kind of far from a checklist or even POH useable item in flight.
 
In the cirrus we lean until the first peak.
Keep leaning until the the last peak is detected.
Keep leaning until the last cylinder is between 30 and 50 degrees hotter than peak.
That is when the computer tells you "best economy"
 
SixPapaCharlie said:
In the cirrus we lean until the first peak.
Keep leaning until the the last peak is detected.
Keep leaning until the last cylinder is between 30 and 50 degrees hotter than peak.
That is when the computer tells you "best economy"
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How do you get hotter than peak?
 
 
rookie1255 said:
Read them all. Reading and nodding my head up and down is one thing, going up and then figuring out what I'm doing in flight is always different. So say I do the big mixture pull and all my cylinders are LOP and outside the "red box." Then I enrichen until the 1st cylinder peaks. Then I want to lean again to get that cylinder away from peak.

So I should shoot for 20-30 degrees LOP for THAT cylinder then, and that 20-30 degrees is 20-30 degrees based on the exhaust gas temperatures. Cylinder head temperatures should automatically be under 400 since I'm 20-30 degrees LOP. If cylinder head temperature for that one cylinder is at or close to 400, then I should keep leaning to bring the temperature down. Does that sound pretty good?

I'm looking for a procedure that can be condensed and used in flight that I can also understand. The articles about the mixture knob in different phases of flight is pretty good, but still kind of far from a checklist or even POH useable item in flight.
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In my opinion, you are nowhere near knowledgeable enough to put his practices into application.

If you absolutely have to go out and do this, do it above 8,000 MSL, where your normally aspirated engine cannot produce enough power to damage itself.

If you have nothing in the airplane as far as accurate engine information, good luck.
 
Cpt_Kirk said:
In my opinion, you are nowhere near knowledgeable enough to put his practices into application.



If you absolutely have to go out and do this, do it above 8,000 MSL, where your normally aspirated engine cannot produce enough power to damage itself.



If you have nothing in the airplane as far as accurate engine information, good luck.
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He's trying to learn, that's the whole point of this thread, right?
 
dans2992 said:
He's trying to learn, that's the whole point of this thread, right?
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Yes, it's fine and I understand the point.

I read and re-read those articles many times to be sure I would be able to understand what's going on underneath the cowling at all times. He's trying to walk before he crawls, in my opinion.
 
Cpt_Kirk said:
Yes, it's fine and I understand the point.

I read and re-read those articles many times to be sure I would be able to understand what's going on underneath the cowling at all times. He's trying to walk before he crawls, in my opinion.
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Your advice for him to get above 8,000 ft to try those things was good.
Your other comments were needlessly sarcastic.
 
JOhnH said:
Your advice for him to get above 8,000 ft to try those things was good.
Your other comments were needlessly sarcastic.
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or....assuming he knows how to set 65% power....that'd be just as adequate as climbing to 8,000 feet WOT. :yes:
 
Checkout_my_Six said:
or....assuming he knows how to set 65% power....that'd be just as adequate as climbing to 8,000 feet WOT. :yes:
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That's true. But I like to suggest going to 8,000 ft for experimenting. It gives you time to get over your "oh sh..., what did I do" moment, and then it gives you time to recover before you land in the middle of someone's picnic.
 
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