LOP

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runner4065

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runner4065
I have an IO-520. I'm installing an engine monitor and GAMI's. How many degrees lean of peak should I run it? What drives this determination (how many degrees LOP)?
 
I don't have balanced injectors, but they were close enough for me on my factory new IO-540. I run 30-40 LOP at 65% power or less. I can run more than that with $1200 worth of fine wire plugs. If one has balanced injectors, you may see 75-100 LOP, and still run smooth. It all depends on how much speed you want to give up. My engine runs better with closer exh temp peaks at around 10-13K, 10.5 gal @ 160 ktas.
 
What does the manufacturer recommend?

Be sure you're aware of the ends and outs of running LOP. Fuel is much cheaper than cylinders.
 
Read and understand the Mike Busch article. Understand the red box.


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I just read that and some of his other articles. What I'm taking away is that it doesn't matter where you run it LOP as long as it is rich enough to run smoothly and lean enough to keep CHT's cool. Between these limits it is a function of efficiency vs. power. And Mike Busch doesn't lean (LOP) based on EGT. He simplifies it to CHT.


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As power settings change (via throttle changes), does that change LOP settings based on EGT (degrees off peak)? I realize this may be less relevant if leaning LOP based on CHT as Mike Busch suggests.
 
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Ryanb said:
What does the manufacturer recommend?

Be sure you're aware of the ends and outs of running LOP. Fuel is much cheaper than cylinders.
Click to expand...

Lean it correctly and it's actually easier on the heads/cylinders. Always a good feeling to see the CHTs come down during LOP operation.
 
runner4065 said:
As power settings change (via throttle changes or altitude changes on a normally aspirated engine), does that change LOP settings based on EGT (degrees off peak)? I realize this may be less relevant if leaning LOP based on CHT as Mike Busch suggests.
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Yes. With altitude changes, you should re-lean. I have had a couple of conversations with Lycoming guys (I have an IO-540) and they say that they believe in the benefits of LOP, but caution that the pilot must understand it and know how to use and pay attention to their engine monitor. They say that their biggest concern is that the pilot running LOP won't monitor any changes due to environmental (altitude, etc) changes close enough.

I run at 65% power, and therefore don't have to deal with the "red box". Above about 8000' msl in a NA engine, power goes down to where it is again down to or below 70%. Hard to damage at those power settings, but still possible to run too rich.

Disclaimer: I am not an expert, other than running my engine for over 1100 hours, taking it close to 2000 hours (tbo) since OH, and it is still running strong, with comps in the high 70's and not making metal in regular analysis. Every annual, my mech tells me to keep flying it with whatever technique I am using.

Take the APS (advanced pilot.com) course. You will learn a lot. AvWeb has a ton of great articles about the subject. Interesting that there are still pilots resisting the benefits of LOP. They are generally an older generation, also reluctant to use GPS over VOR or ADF, reluctant to use glass over steam. To each their own. Some planes are just better with steam.
 
SoCal RV Flyer said:
Lean it correctly and it's actually easier on the heads/cylinders. Always a good feeling to see the CHTs come down during LOP operation.
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Point was, if you don't understand what you're doing and do it incorrectly it will have a reverse effect.
 
Good articles above. I picked 4 little balls of lead out of 4 bottom plugs. Compression test 78-79/80. I lean way out for ground operations. I lean every 1000' or so during my climb to maintain my 1250 F takeoff mixture. When leaned in flight, I am seeing 15-16 nm/gal. Not too bad for the family SUV. I have an A&P friend that recommends against LOP operations, because of seeing so many burnt exhaust valves.
 
runner4065 said:
I just read that and some of his other articles. What I'm taking away is that it doesn't matter where you run it LOP as long as it is rich enough to run smoothly and lean enough to keep CHT's cool. Between these limits it is a function of efficiency vs. power. And Mike Busch doesn't lean (LOP) based on EGT. He simplifies it to CHT.


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Click to expand...
pretty much what I do.

I've run thru the initial leaning schemes to "see" that everything is balanced and smooth when leaned. Now that I know that I just pull the mixture to the desired fuel flow and monitor the CHTs. So long as everything is cool, CHTs below 380 F, I don't worry. I usually run around 75% HP....TSIO-520....and that's 25" and 2,500 RPM and around 16 gph.
 
ActiveAir said:
Take the APS (advanced pilot.com) course. You will learn a lot. AvWeb has a ton of great articles about the subject. Interesting that there are still pilots resisting the benefits of LOP. They are generally an older generation, also reluctant to use GPS over VOR or ADF, reluctant to use glass over steam. To each their own. Some planes are just better with steam.
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In the interests of full disclosure, it is not only pilots -- there are A&Ps who are dead set against LOP too, based on their experience working on clients' engines. I had an interesting conversation with some mechanics at Middlebury, VT a couple of years ago. I suspect the folks operating the engines in question weren't taking all the recommended precautions and not watching their engine monitors, if they had them... but the argument was basically that it's difficult enough to do it right that if you aren't an expert, you should probably stay away from LOP. Since I've been running LOP (at <70% power only, usually above 7000 feet) and am not by any stretch an engine specialist, I disagreed that you have to be an expert, but the point is well taken that you should know enough to be able to do it right, and should be diligent enough to actually do it right.
 
do it right?.....like stop and go 100 deg rich if you can't get the CHTs below 380? It ain't all that hard once one knows the engine is capable and setup....after that it's easy peasy.

IMHO....the issue is running at "peak EGT" vs lean. Many do this and not realize the damage it creates.
lycoming%20power%20chart.jpg
 
The problem with "avoiding LOP" on engines without digital monitors, is that it seems to prevent "Best Economy" settings entirely. Unless I'm missing something, the POH procedure for leaning in cruise to best economy is to lean "untill the onset of roughness, then richen just enough to smooth out". This should put one right in the LOP range. The thing I'm debating with myself; is this worth doing when one doesn't have CHT numbers in the cockpit?
 
Do it right == make sure your richest cylinder is always at least 30 dF LOP unless you're operating at 65% power or less. Don't run LOP in the climb (my SOP, I know Mike Busch and others recommend otherwise). I suspect running at peak EGT is only part of the problem; the other part may be pilots thinking they're okay if their LEANEST cylinder is sufficiently LOP. Depending on how well balanced your injectors are, that may not be safe enough.

BTW, even with GAMIs, I can't get my richest cylinder >30dF LOP without some roughness, so I usually run with that cylinder right around or slightly LOP at reduced power only.
 
George Mohr said:
The problem with "avoiding LOP" on engines without digital monitors, is that it seems to prevent "Best Economy" settings entirely. Unless I'm missing something, the POH procedure for leaning in cruise to best economy is to lean "untill the onset of roughness, then richen just enough to smooth out". This should put one right in the LOP range. The thing I'm debating with myself; is this worth doing when one doesn't have CHT numbers in the cockpit?
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It works when your engine is functioning correctly....and if it's not in adjustment you could be heating a cylinder.....but, you wouldn't know that.

Another method is to lean using airspeed. Lean until you loose 3-4 kts. That will put the power low enough not to be a problem and to see nice fuel savings. If all runs well, smooth, there....you'll probably be fine.
 
George Mohr said:
The problem with "avoiding LOP" on engines without digital monitors, is that it seems to prevent "Best Economy" settings entirely. Unless I'm missing something, the POH procedure for leaning in cruise to best economy is to lean "untill the onset of roughness, then richen just enough to smooth out". This should put one right in the LOP range. The thing I'm debating with myself; is this worth doing when one doesn't have CHT numbers in the cockpit?
Click to expand...

Yep everyone flying anything high performance these days should have an engine monitor with all cyl instrumented... I wouldn't fly without one...


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Just remember CHTs are much more of a area of focus than EGTs.

I'm a ROP guy, I lean to book fuel flow then adjust for max 350F cruise and 380max climb, IO-520D, I plan on 15GPH at 120ktas
 
I have a IO-360. I can usually get the first cylinder to peak to around -46 degrees before it starts to lose power and EGTs start going down at that point which gets me closer to peak. I've been running -25 LOP lately. Is that acceptable? I'm concerned about running too close to peak because of detonation.

I plan 135KTAS 8gph LOP - Arrow
 
I was discussing LOP operations with someone and they note the airspeed prior to leaning LOP, then lean, then add MP until airspeed is back to pre LOP speed. This is on a TSIO-520. He also doesn't change leaning settings when changing altitude (except as needed to keep CHT below 380) or power setting.
 
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runner4065 said:
I was discussing LOP operations with someone and they note the airspeed prior to leaning LOP, then lean, then add MP until airspeed is back to pre LOP speed. This is on a TSIO-520. He also doesn't change leaning settings when changing altitude (except as needed to keep CHT below 380) or power setting.


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careful with his advice....he probably has an altitude compensating fuel pump....which most aircraft don't have. Once level his advice works....but if you change altitude you'll have to re-lean.
 
In my airplane over the life of an engine, I can pretty much pay for the overhaul with fuel savings from flying LOP. So even if I shortened my engines life.... but wait, I'm actually exceeding TBO, going strong...


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gsengle said:
In my airplane over the life of an engine, I can pretty much pay for the overhaul with fuel savings from flying LOP. So even if I shortened my engines life.... but wait, I'm actually exceeding TBO, going strong...


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Agree completely. For example my IO-540 at altitude / cruise (65% power) will burn almost 16gph ROP and around 13gph LOP sacrificing about 3 knots TAS. Fuel @ $4.25 / gallon x 3 = $12.75 / hour x 2,000 = $25,500 over the life of the engine. Just going off of today's fuel prices.

This is just a bonus though. From what I gather I should actually extend the engine's life with this practice.
 
Ok here's something I genuinely don't understand. How can one quote a equal percent power at LOP and ROP, and yet have a different airspeed? If it was truly the same %power, the airspeed would be identical, no? (obviously different mixture and throttle settings to get there)

My Piper POH has this same discrepancy, and I've never gotten a satisfactory explanation for it.
 
Tom-D said:
in that case, you simply set horse power with fuel flow.
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cept...it doesn't workie that way. There are more variables than just fuel flow. :no:

That's why folks use airspeed.....and it's the closest way of measuring the power output compared with FF.
 
When I fly the 310 the throttles only come back from WOT when landing. Other that that I use a big pull on the red knobs until I feel/hear the power back off on each engine. Let CHT's stabilize and make small adjustments +/- to keep CHT's where I want which is usually sub 360. I did it a whole bunch the "hard" way of staring at the JPI and fiddling, but the current method is much faster and you end up in the same place.
 
Checkout_my_Six said:
cept...it doesn't workie that way. There are more variables than just fuel flow. :no:

That's why folks use airspeed.....and it's the closest way of measuring the power output compared with FF.
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there are several methods of determining horse power many use the VSI
 
George Mohr said:
Ok here's something I genuinely don't understand. How can one quote a equal percent power at LOP and ROP, and yet have a different airspeed? If it was truly the same %power, the airspeed would be identical, no? (obviously different mixture and throttle settings to get there)

My Piper POH has this same discrepancy, and I've never gotten a satisfactory explanation for it.
Click to expand...

You aren't really at the same % power at a constant MP and RPM if you change the mixture. See the chart posted above.


If you are ROP(for purposes of this discussion lets call that +75* of peak EGT) then you can use the power charts in the POH and get a good approximation of % power. When lop(and normally aspirated), multiply fuel flow by 14.9 to get HP and divide that by rated to get % power. For example the POH on the 310 calls 2500 RPM and 23" MAP at 5000 ft on a standard day 70.9% power or approximately 203 HP per side. It calls for a fuel flow of around 30 GPH to do this. Empirically I know this is going to put me around 75* ROP and CHT's will be...high. However, I can push the throttles up, pull mixture back to 26.2 GPH total and get the same 203 HP per side and have CHT's that will be 360 or below. IIRC, this would put me at about 20-30 LOP assuming I'm WOT.

In other words, I could set my MP and RPM per the POH and voila I'm at 75% power. However, because I've got the plane dialed in I can pull the mixture back until the engines are 100* LOP. One will give me 195 KTAS and the other will give me 165 KTAS. What is my % power? Go by the POH when ROP and multiply by fuel flow when LOP. Now, what happens when I bring the throttles back a bit and leave everything else alone?
 
Some pf the Van's guys are pretty extreme with LOP...to the point of running WOT all the time and adjusting rpm with mixture alone. :eek:

Checkout_my_Six said:
pretty much what I do.

I've run thru the initial leaning schemes to "see" that everything is balanced and smooth when leaned. Now that I know that I just pull the mixture to the desired fuel flow and monitor the CHTs. So long as everything is cool, CHTs below 380 F, I don't worry. I usually run around 75% HP....TSIO-520....and that's 25" and 2,500 RPM and around 16 gph.
Click to expand...

I'm like you in that I use fuel flow as a cross check. Performance cruise is about 2550-2600 rpm (FP prop) and fuel flow is right at about 7 gph when leaned nicely. But it's the CHTs that I'm really monitoring the most. If I'm 150 degrees ROP, the consumption balloons up to 9.5-10 gph at the same settings. I'm too chicken to go LOP at anything below 8000' DA, but a lot of guys do.
 
SoCal RV Flyer said:
Some pf the Van's guys are pretty extreme with LOP...to the point of running WOT all the time and adjusting rpm with mixture alone. :eek:



I'm like you in that I use fuel flow as a cross check. Performance cruise is about 2550-2600 rpm (FP prop) and fuel flow is right at about 7 gph when leaned nicely. But it's the CHTs that I'm really monitoring the most. If I'm 150 degrees ROP, the consumption balloons up to 9.5-10 gph at the same settings. I'm too chicken to go LOP at anything below 8000' DA, but a lot of guys do.
Click to expand...
I'm running a turbo that way....and I'm most concerned with the CHTs....all the way up to 18,000. :D

IF they're all cool....everything is fine. And it really is safer on the lean side provided you know the temps.
 
simtech said:
That was actually a good read...I never heard of the Back Suction Economizer System before. And I swear I started smelling fuel coming off those pages.
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The only difference between that up draft tractor carb and the MA3 we fly with, is that the MA 3 has a mixture valve where the fuel leaves the float bowl.
 
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