Question about LOP

JC150 said:
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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I used to worry about that sort of thing, but now with 20 years of experience flying with non-turbocharged Lycoming engines and JPI engine analyzers, I've come to the conclusion that if you just lean to the first sign of roughness and then enrich just until it smooths out, you get the same result as agonizing over the numbers on the analyzer, and spend a more time with your eyes outside where they belong.
 
Checkout_my_Six said:
maybe not.....not if everything is tuned well. :yes:
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Even if you're smooth as silk as my IO-470s were all the way to falling off completely, by the time lead becomes an issue at the cold side of things you'll be so far off the pipe you couldn't maintain altitude. This could be a minor issue in loading up plugs on a prolonged descent and having a rough engine for landing, but all in all not a major concern for the longevity of the engine. I doubt people can maintain those levels of power enough to cause a problem.
 
Ron Levy said:
I used to worry about that sort of thing, but now with 20 years of experience flying with non-turbocharged Lycoming engines and JPI engine analyzers, I've come to the conclusion that if you just lean to the first sign of roughness and then enrich just until it smooths out, you get the same result as agonizing over the numbers on the analyzer, and spend a more time with your eyes outside where they belong.
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It's typically the easiest way to set a near optimum mixture on those engines and pretty much always ends up LOP unless you have induction problems. Most people were taught to operate LOP during PP training without realizing it.
 
Thanks for the advice. So basically just lean till it gets rough, and then richen slightly and monitor the EGT and CHTs throughout the flight and make sure they dont get too hot? And as long as I'm below 75% I dont need to worry about detonation then?
 
mcpilot said:
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
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Thanks so much for posting the pictures of your valves! Do you feel the reduction in lead deposits was due to LOP ops, or to the TCP additive? I have seriously considered using TCP in my fuel because the cylinders on my plane run really cold all the time. My CHTs are often well under 300 degrees. I have read that when an engine runs this cold, the additives that are already in avgas don't get hot enough to scavenge all the lead. Running LOP makes this even worse because you run even colder.

I have wondered if the TCP only works to get rid of the lead in the fuel during combustion, or if it can remove lead deposits already in your engine and no one has ever been able to answer this. However, your pictures clearly show that you have removed your deposits, so since I run LOP most of the time and I still have deposits, it looks too me that the TCP actually works!
 
mcpilot said:
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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Pretty much 6500' DA gets you there, lower if you have a fixed pitch climb prop. Increase in altitude not only reduces power, it reduces load on a fixed pitch prop (some effect on a constant speed prop as well, not nearly the same amount though). Without supercharging of some form, it's pretty tough to destroy a naturally aspirated aircraft engine on 100LL in normal use.
 
Henning said:
Pretty much 6500' DA gets you there, lower if you have a fixed pitch climb prop. Increase in altitude not only reduces power, it reduces load on a fixed pitch prop (some effect on a constant speed prop as well, not nearly the same amount though). Without supercharging of some form, it's pretty tough to destroy a naturally aspirated aircraft engine on 100LL in normal use.
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to 65% HP?.....most are saying the safe altitudes for leaning to peak EGT wide open throttle are 7-8,000 feet and higher.
 
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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Here is the FAA chart for required detonation margins for certification. This is probably the best and most informative chart of all the charts and graphs that get routinely trotted out in these LOP threads IMO. It's the closest we'll ever get to knowing where detonation actually occurs. Unfortunately, actual data from our individual engines, if it even exists, is not shared with us either by the FAA, or the manufacturers.

Detonationmargin.jpg
 
JC150 said:
Thanks for the advice. So basically just lean till it gets rough, and then richen slightly and monitor the EGT and CHTs throughout the flight and make sure they dont get too hot? And as long as I'm below 75% I dont need to worry about detonation then?
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If your CHTs are steady below 350°, your potential for detonation is next to nothing. If you see it climb, you are entering a regime where you need to exercise caution. Climbing CHT is what you are looking for, that is the hazard sign of detonation.
 
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Dav8or said:
Thanks so much for posting the pictures of your valves! Do you feel the reduction in lead deposits was due to LOP ops, or to the TCP additive? I have seriously considered using TCP in my fuel because the cylinders on my plane run really cold all the time. My CHTs are often well under 300 degrees. I have read that when an engine runs this cold, the additives that are already in avgas don't get hot enough to scavenge all the lead. Running LOP makes this even worse because you run even colder.

I have wondered if the TCP only works to get rid of the lead in the fuel during combustion, or if it can remove lead deposits already in your engine and no one has ever been able to answer this. However, your pictures clearly show that you have removed your deposits, so since I run LOP most of the time and I still have deposits, it looks too me that the TCP actually works!
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I'm not thinking the TCP really matters.. .I think LOP does because of complete combustion. Think of a blow torch and adjust the air mixture. if you are not putting enough air into the fame you get carbon build up-- same with our engines and running too rich-- incomplete fuel burn. Remember that EGT is the same temperature whether LOP or ROP. The additives are activated by the combustion event not the CHT. I think the additives kick in anywhere above 1000 EGT, but Mike Busch can tell you for sure...
 
dell30rb said:
I was about to post the same thing.

I run 50F ROP starting around 9000 feet
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I agree with this strategy. With a NA engine, running LOP over 9,000 is just too little power and too slow. We need all the power we can get up there and there is no way we can be over 65%.
 
mcpilot said:
I'm not thinking the TCP really matters.. .I think LOP does because of complete combustion. Think of a blow torch and adjust the air mixture. if you are not putting enough air into the fame you get carbon build up-- same with our engines and running too rich-- incomplete fuel burn. Remember that EGT is the same temperature whether LOP or ROP. The additives are activated by the combustion event not the CHT. I think the additives kick in anywhere above 1000 EGT, but Mike Busch can tell you for sure...
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Then I have ask, why do you bother with the added expense and headache of adding the TCP? Have you discontinued it's use and do you still have clean cylinders? Like I said, I have run LOP for several years now and still have lead deposits on my pistons when I peer in the spark plug hole with a flashlight. Your pictures suggest too me that the TCP actively works to remove old deposits.
 
I am not currently using TCP... I will re borescope and see if there is a difference.
 
Dav8or said:
I agree with this strategy. With a NA engine, running LOP over 9,000 is just too little power and too slow. We need all the power we can get up there and there is no way we can be over 65%.
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Then you should put on a turbo or buy something that does the speed you want while still running LOP. I bought a 310 because I wanted 180kts but I wanted to do it loafing a pair of capable engines. My turboed Travelair was great, especially around the mountains, but lacked speed down low where I like to fly. When I flew the 310 down low I would still be WOT (28")and 2500rpm, by those numbers you'd think I was at some high power percentage, but my fuel flow was leaned 11.2gph per side, so the engines were just up on the pipe. Yes, I give up airspeed and have a TAS of 165kts down low, but my CHTs are all good around 330°-340°. If you want to drive down low you just adjust mixture to CHT and let airspeed fall where it may. When I land, my exhaust and augmenters would be lined with a dusting of white lead. Borescope showed clean valves, plugs looked good after 100hrs.
 
Henning said:
It's typically the easiest way to set a near optimum mixture on those engines and pretty much always ends up LOP unless you have induction problems.
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My experience in several thousand hours with such engines and analyzers is you end up right around peak, not LOP in more than one or two cylinders, but YMMV.
 
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JC150 said:
Thanks for the advice. So basically just lean till it gets rough, and then richen slightly and monitor the EGT and CHTs throughout the flight and make sure they dont get too hot?
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Pretty close -- monitor the CHT's to keep them right. EGT's don't really mean much unless they read significantly different from what they normally read.

And as long as I'm below 75% I dont need to worry about detonation then?
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Pretty much, as long as you keep the power settings within the ranges your POH recommends, i.e., don't go pulling the RPM back to 1800 with full throttle at low altitude or some such silliness.
 
Henning said:
Then you should put on a turbo or buy something that does the speed you want while still running LOP.
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Great idea! I'll just need your account number and routing number and I'll order one right up! :rolleyes:

I don't fly above 9,000 ft very often, so how about this? I just run ROP above 9,000 and save the money of a new plane. All the new engine gurus that get quoted on the net over and over again will tell you that there is nothing wrong with running ROP at any setting when you're at 65% and under and your CHTs are 380 and under. Over 9,000 ft, WOT and 2500 or less and I'm under 65%. I will dial in 50 ROP and monitor CHTs. My engine runs cold, so CHTs are rarely a problem. The only way I can get my rear cylinders to 380 is on climb out on a hot summer day.
 
Dav8or said:
That would be great! How long did you use the TCP?
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A couple of months.. Then I talked to Mike Busch and he said it doesn't hurt but there are already lead scavenging compounds in the Avgas now... I still might put it in if I remember... Sure can't hurt
 
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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There was a report circulating last fall from, I believe, Cubcrafters in which they tested engine analyzers from EI, JPI, and one other. The conclusion relating to EI was that their standard ungrounded bayonet CHT probes showed temperatures up to 50 degrees F lower than grounded probes from JPI and the other supplier.

I did some looking online and was able to find a reference to the probe type that was used by Lycoming in certifying my O-360, and it was a grounded type. So to be safe, I add 50F to the CHT reading of my EI CGR-30P engine analyzer.

I believe in the likelihood of a EI low CHT bias because my Tiger gives me readings much like yours. Even in the hottest summer day in climb my hottest CHT didn't reach 335F. 30-50F hotter (365-385F) is a more credible temperature range. In the winter, peak CHTs range from 285-305F.

So be a little careful with your EI UBG-10 CHTs. If they use the standard ungrounded EI probes, they could be reading 50F low.
 
my CHT probes read OAT temp prior to starting.....that's an indication they're working....maybe not at operating temps, but it's enough for me.
bkspero said:
There was a report circulating last fall from, I believe, Cubcrafters in which they tested engine analyzers from EI, JPI, and one other. The conclusion relating to EI was that their standard ungrounded bayonet CHT probes showed temperatures up to 50 degrees F lower than grounded probes from JPI and the other supplier.

I did some looking online and was able to find a reference to the probe type that was used by Lycoming in certifying my O-360, and it was a grounded type. So to be safe, I add 50F to the CHT reading of my EI CGR-30P engine analyzer.

I believe in the likelihood of a EI low CHT bias because my Tiger gives me readings much like yours. Even in the hottest summer day in climb my hottest CHT didn't reach 335F. 30-50F hotter (365-385F) is a more credible temperature range. In the winter, peak CHTs range from 285-305F.

So be a little careful with your EI UBG-10 CHTs. If they use the standard ungrounded EI probes, they could be reading 50F low.
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Checkout_my_Six said:
my CHT probes read OAT temp prior to starting.....that's an indication they're working....maybe not at operating temps, but it's enough for me.
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I apologize if my note suggested that EI probes are incapable of reading an accurate temperature. They are as accurate as any. And as you have seen, when the engine is at a uniform temperature (cold prestart) and not making power, EI probes will read the same as any other. The issue only develops when the engine is making power (i.e., there is a heat source in the combustion chamber) and heat is being dissipated through the cylinder head to the cooling fins. Grounded probes (like JPI's and what I understand were the configuration used in certification testing of at least Lycoming O-360 engines) have the thermocouple junction essentially in direct contact with the base of the sensor well where the temperature is hottest.

EI's ungrounded probes are slightly removed from that position in a somewhat cooler location. When I purchased my CGR-30P I understood the difference in designs and the "theoretically" lower temperature that might be sensed by the EI probes, but expected the difference to be only a degree or two. Instead, the article indicated that the actual difference is up to 50 degrees F. I don't see how the difference could be that large, but the testing seems very well done and I can't find fault with it in any material way.

The issue is that the probe design differences cause each type to measure temperature in a slightly different spot in the sensor well of an engine, and that tiny difference in locations represents up to a 50F difference in temperature at the thermocouple junction. If the engine temperature limits were set using ungrounded probes, then there would be no issue. Unfortunately, as I understand things, the temperature limits were set using grounded probes. So an engine operating at the CHT limit measured using an EI ungrounded probe could have CHTs as much as 50 degrees F hotter than Lycoming was intending. That's why I give myself a 50F safety margin for CHT.
 
50 deg F difference is huge.....I'd need to understand more about this "ungrounding" thing. It's a new one for me.....

Now, if it's location we're discussing and not a "type" of thermocouple....then I could understand your reasoning.

The differences I'm use to are bayonet types vs. spark plug ring types.....and either come in J or K type thermocouple wire.
 
mcpilot said:
A couple of months.. Then I talked to Mike Busch and he said it doesn't hurt but there are already lead scavenging compounds in the Avgas now... I still might put it in if I remember... Sure can't hurt
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Yes, there are lead scavenging additives already in avgas, but I have read that they aren't very effective if CHTs are too low. I'm mostly interested in cleaning up the lead build up I have, rather than continual use forever. The stuff sounds pretty scary to handle and it's expensive. My hope is to use it for awhile until the pistons are clean and then just continue normal LOP ops. Your pictures are the first evidence that I have seen anywhere that TCP might be useful in cleaning up a preexisting condition.
 
bkspero said:
There was a report circulating last fall from, I believe, Cubcrafters in which they tested engine analyzers from EI, JPI, and one other. The conclusion relating to EI was that their standard ungrounded bayonet CHT probes showed temperatures up to 50 degrees F lower than grounded probes from JPI and the other supplier.

I did some looking online and was able to find a reference to the probe type that was used by Lycoming in certifying my O-360, and it was a grounded type. So to be safe, I add 50F to the CHT reading of my EI CGR-30P engine analyzer.

I believe in the likelihood of a EI low CHT bias because my Tiger gives me readings much like yours. Even in the hottest summer day in climb my hottest CHT didn't reach 335F. 30-50F hotter (365-385F) is a more credible temperature range. In the winter, peak CHTs range from 285-305F.

So be a little careful with your EI UBG-10 CHTs. If they use the standard ungrounded EI probes, they could be reading 50F low.
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How do they know that the JPI probes aren't reading 50 degrees too high?
 
Well, I did another flight this morning. 0*C OAT, 21/24 at 7,000 ft per POH for 65%. I was getting about 8 GPH and getting 1220 EGT 272 CHT on my hottest cylinder (#3).

I leaned until I saw the EGTs start to drop and then continued leaning until the engine got a little rough and richened slightly. This gave me about 8gph. What I am very confused on is when I moved the mixture slightly more rich (up to about 9gph), the engine got louder and i felt the plane accelerate and it seemed like it was getting more power but I was still lean of peak egt yet the EGT was slightly higher at 9gph vs 8gph.

Was I running it too LOP?
 
20 deg lean will be something like 3 knots less on the indicated airspeed.....and yes when you add back the mixture you will have more power.
 
Dav8or said:
How do they know that the JPI probes aren't reading 50 degrees too high?
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Both probes are reading accurately....only in different locations where the temperatures are different. So in my opinion the probe that is indicating the "proper" temperature is the probe that is in the same location as the one that was used by the engine manufacturer to set the CHT limits for that engine. And while I own an EI engine analyzer, I believe that JPI probes read CHT temperature in a location that is closer to that of the AN5541 probes used by Lycoming in testing.

Here is a link to the original report, EI's rebuttal, and the reference to the AN5541 thermocouple. It is on the Red Board.

http://forums.aopa.org/showthread.php?t=92650&highlight=EI+response
 
Here's a typical LOP scenario in the Cirrus I owned:

15443710724_5ab9e311f2_c.jpg


OK, maybe the tailwind and groundspeed weren't quite typical*.

Still, you can see its LOP at 12.9 gph at 7,000', resulting an a TAS of 167k. Shows just over 300º CHT. The 70% power figure was typically not accurate LOP.

Sure, I could go ROP and see maybe 180k, but that would result in much higher fuel flow and really only take 5 to 15 minutes of time off a flight at a huge cost in gas.


*This was flying back to FL after vacating to N GA from S FL for Hurricane Jeanne in 2004 and getting pushed along by the outer effects. Oddly smooth just outside of the hurricane's fury:

15878782560_f42bb6a334_z.jpg


16066069045_5e0925b706_z.jpg
 
What would the fuel flow be if you went ROP?
 
Johann said:
What would the fuel flow be if you went ROP?
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Honestly, I did it so rarely I'd have to guess.

My guess would have been about 18 gph or so - an extra 5 gph to go maybe 13k faster.

But leaning by placard to "Best Power" gives this:

16077248261_3198186d6b.jpg


Interpolating, that looks like over 21 gph at 7,000'.

In any case, far from a trivial difference, especially when the time saved on any reasonable leg is measured in minutes.
 
Geico266 said:
Anything above 8000' and you can run peak.
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Peak is not the hardest on the engine though, 75°ROP or so is short term, and anything richer in the long term. It's carbon and lead deposits on valves and seats that costs people the most maintenance money, the fact that you pay extra in operating cost to cause these extra maint costs just adds to the total excess it costs to run ROP. ROP operations basically doubles the long term operating costs.
 
Ron Levy said:
I used to worry about that sort of thing, but now with 20 years of experience flying with non-turbocharged Lycoming engines and JPI engine analyzers, I've come to the conclusion that if you just lean to the first sign of roughness and then enrich just until it smooths out, you get the same result as agonizing over the numbers on the analyzer, and spend a more time with your eyes outside where they belong.
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I've never gotten our Lyc IO-360 to run rough as compared to the Lyc O-320's I trained in. I've gotten it to "big pull" though, but rough.....nah. Perhaps I need a reference, because I have leaned to where I was concerned about the way it was running, but I still wouldn't call it rough.

I've also never gotten it to quit in flight, and I don't quite have the gumption to do it yet either.

To me, that's the biggest difference in IO and O engines is that with an O, you can certainly tell that it's running rough.
 
Henning said:
Peak is not the hardest on the engine though, 75°ROP or so is short term, and anything richer in the long term. It's carbon and lead deposits on valves and seats that costs people the most maintenance money, the fact that you pay extra in operating cost to cause these extra maint costs just adds to the total excess it costs to run ROP. ROP operations basically doubles the long term operating costs.
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But...but....but....the engine stands a better chance of making TBO :D
 
Jaybird180 said:
I've never gotten our Lyc IO-360 to run rough as compared to the Lyc O-320's I trained in. I've gotten it to "big pull" though, but rough.....nah. Perhaps I need a reference, because I have leaned to where I was concerned about the way it was running, but I still wouldn't call it rough.

I've also never gotten it to quit in flight, and I don't quite have the gumption to do it yet either.

To me, that's the biggest difference in IO and O engines is that with an O, you can certainly tell that it's running rough.
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You can also crack the carb heat as your last bit of leaning and that helps smooth thing out.
 
FastEddieB said:
Honestly, I did it so rarely I'd have to guess.
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Many planes (like Bo's) have the fuel flow gauge marked as well. Rather than firewalling the red knob, you move the needle to the appropriate altitude index.
I don't know how accurate it is.
 
flyingron said:
Many planes (like Bo's) have the fuel flow gauge marked as well. Rather than firewalling the red knob, you move the needle to the appropriate altitude index.
I don't know how accurate it is.
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All factory FI planes have a 'fuel flow' gauge which actually is a fuel pressure gauge calibrated in flow. As long as the FI system is as designed, then the gauge will be accurate. If it is out of adjustment or has different nozzles, it may not be correct for flow.
 
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