Question about LOP

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JC150

Pre-takeoff checklist
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JC150
I want to try LOP with my Piper arrow 3. My question is how many degrees LOP should I be running at with an IO-360? I looked for an answer in the POH but had no luck. Thanks!
 
Have you run the GAMI test? Do you know when all cylinders are LOP? That's your starting place, after that lean for the fuel burn or airspeed you want.

Read/watch the info suggested.
 
If all cylinders are LOP within .5 GPH or less (verified with the lean test).....20-30 deg LOP is the optimum at 75% HP....more lean will not hurt a thing, just lower CHTs.
 
If you have an engine analyzer, you set LOP on the richest (i.e., last to peak). I use 25 on my contienental. Your n/a lycoming shouldn't care as long as all the cyls are on the lean side.
 
Keep it under 65% power and it doesn't matter. I normally run about 50 degrees LOP. My engine will run leaner but there is a power tradeoff.
 
Sac Arrow said:
Keep it under 65% power and it doesn't matter. I normally run about 50 degrees LOP. My engine will run leaner but there is a power tradeoff.
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So how are you determining percent power? If you go by the MP/RPM settings in the POH, you'll find they assume a couple more GPH that what you'd see LOP... Therefore even if you're running the MP/RPM for "65%" by the book, your lower fuel flow reduces the power further, right?
 
Typically I set the MP/RPM to a best power mixture book value that is 75%. For my plane and probably an Arrow III, that is about 25 squared.

Then I lean. You will lose at least 10% power going from best power mixture to about 30F LOP. So you're going to be under 65% power
 
dans2992 said:
So how are you determining percent power? If you go by the MP/RPM settings in the POH, you'll find they assume a couple more GPH that what you'd see LOP... Therefore even if you're running the MP/RPM for "65%" by the book, your lower fuel flow reduces the power further, right?
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That's right. I set it at book value 65% to be conservative then lean from there. In reality, I'm probably getting more like 55% power. One thing that is important to note is that once you are LOP, it's fuel flow that primarily determines power, not manifold pressure.

dell30rb said:
Typically I set the MP/RPM to a best power mixture book value that is 75%. For my plane and probably an Arrow III, that is about 25 squared.

Then I lean. You will lose at least 10% power going from best power mixture to about 30F LOP. So you're going to be under 65% power
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Sounds about right.
 
To determine % power you can use airspeed. Run at 65% power according to POH, normal leaning. Note airspeed. Now run at that airspeed but leaned. That will be 65% too.
 
coloradobluesky said:
To determine % power you can use airspeed. Run at 65% power according to POH, normal leaning. Note airspeed. Now run at that airspeed but leaned. That will be 65% too.
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Er, my understanding is that drag increases non-linearly with airspeed. So double power does not mean double airspeed, and 65% airspeed does not mean 65% power.
 
mcmanigle said:
Er, my understanding is that drag increases non-linearly with airspeed. So double power does not mean double airspeed, and 65% airspeed does not mean 65% power.
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That's not what he said
 
mcmanigle said:
Er, my understanding is that drag increases non-linearly with airspeed. So double power does not mean double airspeed, and 65% airspeed does not mean 65% power.
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You don't understand it. That is for sure. Try reading what I posted until you get it. Note I said "the same airspeed". If 65% power gets you 150 knots running rich, it will take 65% power to get you 150 knots running lean. It is POWER that makes an airplane GO! When you run 65% power running lean, you do it ON LESS FUEL!
 
coloradobluesky said:
You don't understand it. That is for sure. Try reading what I posted until you get it. Note I said "the same airspeed". If 65% power gets you 150 knots running rich, it will take 65% power to get you 150 knots running lean. It is POWER that makes an airplane GO! When you run 65% power running lean, you do it ON LESS FUEL!
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To a limited extent. That assumes you don't change the throttle position.
 
It is based on this logic.

If 65% power equates to 150knots
then 150knots equates to 65% power
 
OP I have an Arrow II. Select 2400, WOT, 6-9k, and pull it to 8.0-9.0gph. If it gives ya smooth operation there you're winning. 130-135. Done. No need for gami vodoo or 20 page dissertations over nth degree egt/cht differentials and detonation straw man arguments ad infinitum. You're welcome. :D
 
Mike Busch says that CHT is really the end point. If it is acceptable for your engine (all cylinders measured) and you are LOP you are safe.
 
mcpilot said:
Mike Busch says that CHT is really the end point. If it is acceptable for your engine (all cylinders measured) and you are LOP you are safe.
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I think that's a bit of an oversimplification. It's possible to be so LOP that you're not developing enough heat to keep the thermally-activated lead scavenging agents working, although the engine would probably be running rough as a cob at that point.
 
Ron Levy said:
I think that's a bit of an oversimplification. It's possible to be so LOP that you're not developing enough heat to keep the thermally-activated lead scavenging agents working, although the engine would probably be running rough as a cob at that point.
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I think it was in the context of staying out of the "Red Box" The lead scavenging compound activation is as a result of EGT. His idea is to have the combustion even to to occur as to minimize ICP

Hi Ron... long time no see BTW... I sold my Tiger over 15 years ago!! Time "flys"
 
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Ron Levy said:
I think that's a bit of an oversimplification. It's possible to be so LOP that you're not developing enough heat to keep the thermally-activated lead scavenging agents working, although the engine would probably be running rough as a cob at that point.
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maybe not.....not if everything is tuned well. :yes:
 
I did a test flight and was doing about 22/24 at 6000 feet and 7gph. The engine analyzer has a find LOP function from the first cylinder that peaked (#3) and I just went to 25 degrees from that. Does this sound correct? I tried leaning further but the engine just got really rough like it was about to die so I stayed at 20LOP
 
After watching Mike Busch's basic leaning video, why wouldn't we just go straight for PEAK? That seems like the best compromise between efficiency, power, and engine wear. Did I miss something?
 
cylinder heat is a stressor your engine won't like for reliability....more specifically CHT heat.
 
ahkahn said:
After watching Mike Busch's basic leaning video, why wouldn't we just go straight for PEAK? That seems like the best compromise between efficiency, power, and engine wear. Did I miss something?
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Peak EGT is that point where all of the fuel is being burned. The scientific term for this is max stoichiometric oxidation. It simply means that there is the proper quantity of oxygen to allow 100% of the fuel molecules to combust. Going speak of that level adds cooling because now you have an excess of air in the cylinders-- marathon you need to burn all of the fuel so this effectively cools the engine.

At a certain altitude and power setting you may safely run at peak EGT. You will get max power and efficient full burn at that level. lean of that point you get increased calling lower fuel burn and less power. You are effective using mixture to control power instead of the throttle.

I have a 95 Mooney 201 and took borescope pics before and after installing a JPI 830 and running LOP. The valves are cleaner.

Comparison9713_zps921658f9.jpg
 
JC150 said:
I did a test flight and was doing about 22/24 at 6000 feet and 7gph. The engine analyzer has a find LOP function from the first cylinder that peaked (#3) and I just went to 25 degrees from that. Does this sound correct? I tried leaning further but the engine just got really rough like it was about to die so I stayed at 20LOP
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You should gauge LOP by going off of the last cylinder to peak. Depending on your analyzer (you really should use one) leaning too fast or too slow will affect results. EI probes are slow response and JPI are fast response probes.
 
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JC150 said:
I did a test flight and was doing about 22/24 at 6000 feet and 7gph. The engine analyzer has a find LOP function from the first cylinder that peaked (#3) and I just went to 25 degrees from that. Does this sound correct? I tried leaning further but the engine just got really rough like it was about to die so I stayed at 20LOP
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No. If you're going to run LOP you need to use the last cylinder to peak. If you have a JPI you tell the lean find mode whether you want LOP or ROP (it confirms this when you tap the right button to enter that mode).
 
JC150 said:
I did a test flight and was doing about 22/24 at 6000 feet and 7gph. The engine analyzer has a find LOP function from the first cylinder that peaked (#3) and I just went to 25 degrees from that. Does this sound correct? I tried leaning further but the engine just got really rough like it was about to die so I stayed at 20LOP
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My guess is that #3 is 20 LOP, and the others are between that and 25 ROP, but that's only a guess. You'd need to download and analyze the data to get a better idea. My personal experience with a lot of Lycoming engines and analyzers is that if you lean to roughness and then enrich just back to smoothness, you'll get all cylinders grouped closely around peak EGT, and that's a real good place to run those engines.
 
ahkahn said:
After watching Mike Busch's basic leaning video, why wouldn't we just go straight for PEAK? That seems like the best compromise between efficiency, power, and engine wear. Did I miss something?
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In some engines, that's a good idea. However, in the big-bore Continentals like you find in a Cirrus SR22, the CHT's may be running rather too hot for best engine longevity, and leaning further brings those CHT's down dramatically.
 
At 6,000 feet and 22/24, the highest CHT I got was on #3 which was 298 and the highest EGT was about 1300. I have the UBG-16.

I read that the detonation zone is between peak and 50ROP. So if i was running the #3 cylinder at 20LOP and the others at 25 ROP, did I technically put them in the detonation zone? This was a 4.5 hr flight...
 
JC150 said:
At 6,000 feet and 22/24, the highest CHT I got was on #3 which was 298 and the highest EGT was about 1300. I have the UBG-16.

I read that the detonation zone is between peak and 50ROP. So if i was running the #3 cylinder at 20LOP and the others at 25 ROP, did I technically put them in the detonation zone? This was a 4.5 hr flight...
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At 22" MP and 2400 rpm you are not able to produce enough power to be concerned about detonation. Even best power (50F ROP) you are not going to make over 65% power
 
dell30rb said:
At 22" MP and 2400 rpm you are not able to produce enough power to be concerned about detonation. Even best power (50F ROP) you are not going to make over 65% power
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and power is related to combustion pressure....so under an acceptable power level....combustion pressures will not hurt things or cause detonation.

depending on the manufacturer.....65% HP for CMI and 70% HP Lycoming....leaning to peak EGT is OK.

Leaning when above those HP levels should be done with care and monitoring....IMHO. If your engine is not conforming (poor ignition or poor fuel distribution)...it likely will run rough leaned beyond peak EGT.
 
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JC150 said:
At 6,000 feet and 22/24, the highest CHT I got was on #3 which was 298 and the highest EGT was about 1300. I have the UBG-16.
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It's pretty cold this time of year, and it's not clear what %HP you were running (22/24 sounds like 65% or so, which isn't exactly "high cruise"), so that CHT by itself doesn't tell us a lot. Same with a snapshot EGT reading. One would need to review the complete data download to really tell anything useful.

I read that the detonation zone is between peak and 50ROP.
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Where did you read that? Detonation is more a function of low RPM and high power setting (or low octane fuel, but I'm assuming you're not putting 80/87 avgas or the like in it) than anything else, and your MP was well below the detonation limit line in the Lycoming IO-360-C-series engines (yours is a C1C6, right?) for 2400 RPM. The limiting MP at 2400 RPM is 28 inches, and 22 inches is so low that the lower RPM limit doesn't even reach that point (bottom corner is 25 inches at 1800 RPM).

So if i was running the #3 cylinder at 20LOP and the others at 25 ROP, did I technically put them in the detonation zone? This was a 4.5 hr flight...
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At 65% power? Nowhere near detonation.
 
Thanks for the responses. The last plane I owned was a C172N, and I leaned that by leaning until peak EGT and left it there. Now that I've stepped up to this Arrow III, I'm still trying to figure out how to lean it properly and this whole ROP vs LOP is still confusing to grasp still for me. I understand the difference, but I dont know what values to use such as 25 LOP or 50 ROP or peak. I never run above 65% power. Also a side note, WOT at 6000' gave me 22", yet I was able to pull the throttle back almost half way and it was still giving me 22", the only thing that was happening was a reduction in fuel flow. The POH says 65% is about 22", so should I be leaving it WOT or pulling it back until the MP starts to decrease?
 
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dell30rb said:
I was about to post the same thing.

I run 50F ROP starting around 9000 feet
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At 9000 feet on a normally aspirated engine you can most probably run anywhere on the chart without harming the engine
 
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