Commercial Pilots who don't know about piston engines
And by Sunday WAY TOO old for her. 
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Jabawocky
That claim does not exactly dovetail with information on the GAMI website:
I can teach anyone to fly safely LOP in under 5 minutes, more like 2-3 minutes including a briefing and demonstration....it is as easy as level out in the cruise, (close your eyes for about 3 seconds while quickly moving the mixture leaner. As soon as you feel the deceleration - stop. Open eyes....This technique works at 500' and WOT/max rpm...how do I do it sans an EMS, the Big Mixture Pull works every time. And yes that is a carby engine.
Not all GA engines can run safely LOP. Carbureted engines, for example, lack precise fuel/air metering systems and typically run rough and lose power LOP. And electronic engine monitors that show cylinder head and exhaust gas temperatures for every cylinder are necessary for safe LOP operations. Graphic engine monitors are even better.
...carbureted engines, and those without engine monitors, can and are being damaged from pilots running them too lean. “We’ve never had any issues with lean-of-peak operations in engines equipped with GAMI injectors and graphic engine monitors,” Middlebrook said. “But we’re also seeing burned valves and cylinder damage in carbureted engines or those with single-point EGTs trying to fly lean of peak. If you don’t have matched fuel injection nozzles and a six-point engine monitor, you just don’t have enough information for lean-of-peak operations.”
...carbureted engines, and those without engine monitors, can and are being damaged from pilots running them too lean. “We’ve never had any issues with lean-of-peak operations in engines equipped with GAMI injectors and graphic engine monitors,” Middlebrook said. “But we’re also seeing burned valves and cylinder damage in carbureted engines or those with single-point EGTs trying to fly lean of peak. If you don’t have matched fuel injection nozzles and a six-point engine monitor, you just don’t have enough information for lean-of-peak operations.”
That's because many engines come out of the manufacturer or maintenance shop with poorly set up fuel/induction systems. Staying ROP helps to cover up the poor quality.
The curves Jabba has posted many times shows why: The slope of the power curve LOP is steeper than ROP, and therefore differences in the power output of each cylinder as a consequence of the imbalances in F/A in to each cylinder become more evident LOP. "Lean misfire" and "roughness" while leaning is actually vibration caused by the imbalance in the power outputs of different cylinders.
The term "conforming engine" is shorthand for one that's been set up properly. That said, my understanding is that some carbureted engines are notoriously difficult to run smoothly ROP, because there isn't much that can adjusted to deal with imbalance problem.
Some people are happy to throw fuel at the problem caused by poor manufacture or maintenance. That's their decision. The main safety message they need to understand is the need to ensure all cylinders are operating sufficiently ROP. That's because the setting that puts the cylinders under the most pressure and temperature stress is, in fact, a setting ROP: around 50 degrees F ROP.
That's also why an engine monitor is important, even if you don't want to operate LOP.
The curves Jabba has posted many times shows why: The slope of the power curve LOP is steeper than ROP, and therefore differences in the power output of each cylinder as a consequence of the imbalances in F/A in to each cylinder become more evident LOP. "Lean misfire" and "roughness" while leaning is actually vibration caused by the imbalance in the power outputs of different cylinders.
The term "conforming engine" is shorthand for one that's been set up properly. That said, my understanding is that some carbureted engines are notoriously difficult to run smoothly ROP, because there isn't much that can adjusted to deal with imbalance problem.
Some people are happy to throw fuel at the problem caused by poor manufacture or maintenance. That's their decision. The main safety message they need to understand is the need to ensure all cylinders are operating sufficiently ROP. That's because the setting that puts the cylinders under the most pressure and temperature stress is, in fact, a setting ROP: around 50 degrees F ROP.
That's also why an engine monitor is important, even if you don't want to operate LOP.
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Lead Balloon
Sure but that is the basis of my point, not an answer to it.
Yes, but:
Here is a selection of quotes from the GAMI website:
"Lean misfire" and "roughness" while leaning is actually vibration caused by the imbalance in the power outputs of different cylinders.
many engines come out of the manufacturer or maintenance shop with poorly set up fuel/induction systems...The term "conforming engine" is shorthand for one that's been set up properly
"even if you have a brand new perfect factory engine, that has a perfectly calibrated set of factory fuel injectors in the engine, with a perfect set-up on the fuel system, the engine is still not going to run smooth" (George Braly, GAMI)
So how do you get a carburetted engine with "fuel/air ratio's that are near to equal on all cylinders", ready for jabawocky's 'eyes closed, big mixture pull, feel the decel = safe LOP even at 500'/full power, engine monitor not required' technique? Genuine question.Here is a selection of quotes from the GAMI website:
"Not all GA engines can run safely LOP. Carbureted engines, for example, lack precise fuel/air metering systems and typically run rough and lose power LOP
...it's not just a matter of pulling back on the mixture. The airplane and engine must be properly equipped for lean of peak operations otherwise you can do serious serious damage to the engine..
You need balanced fuel injectors and a good multi probe engine analyser that shows EGT and CHT for all the cylinders. A single probe EGT/CHT set-up is just not acceptable
If you don’t have matched fuel injection nozzles and a six-point engine monitor, you just don’t have enough information for lean-of-peak operations."
...it's not just a matter of pulling back on the mixture. The airplane and engine must be properly equipped for lean of peak operations otherwise you can do serious serious damage to the engine..
You need balanced fuel injectors and a good multi probe engine analyser that shows EGT and CHT for all the cylinders. A single probe EGT/CHT set-up is just not acceptable
If you don’t have matched fuel injection nozzles and a six-point engine monitor, you just don’t have enough information for lean-of-peak operations."
Last edited by oggers; 11th Feb 2016 at 12:06.
Really enjoyed the various viewpoints. Most of my experience is on turbo props but now owning an IO360 trying to learn as much as i can. I have been setting 25/25 in the climb! I have been keeping CHT under 390 in climb so hopefully not too much problem.
Is this a summary of the 7 pages?
Almost everyone agrees 50 degrees ROP is a no-no because that will correspond to highest CHT and pressure.
If running ROP, just need to make sure it is at least more than 50 degrees, more like 100 degrees?
Running LOP is more controversial but has advocates.
I am not understanding the alternative climb settings that well. Seems to be pretty much high RPM settings and higher throttle settings, within CHT limits?
Is this a summary of the 7 pages?
Almost everyone agrees 50 degrees ROP is a no-no because that will correspond to highest CHT and pressure.
If running ROP, just need to make sure it is at least more than 50 degrees, more like 100 degrees?
Running LOP is more controversial but has advocates.
I am not understanding the alternative climb settings that well. Seems to be pretty much high RPM settings and higher throttle settings, within CHT limits?
Running LOP is more controversial but has advocates.
Extralite,
The above against LOP are contributions to the discussion by the ignorati.
LOP was SOP in all large piston engines, and until recent years, was well covered in the Lycoming engine handbooks --- which went into detail not necessarily to be found in the particular aircraft AFM (by whatever name).
The objections to LOP are a measure of the dumbing down of aviation knowledge.
Tootle pip!!
At the very least this is confusing. The "Continental Guide on Engine Care" seems to suggest that in most cases, we do what this thread seems to suggest we don't, ie run at 50-75 degrees ROP. LOP can be used on some engines for longest range but requires careful monitoring. Is this outdated info?
from "Continetal Guide on Engine Care." http://www.insightavionics.com/pdf%2...ontinental.pdf
High Power Cruise
High power cruise is generally defined as power settings between 65 and 74% of rated engine power. In this
range, TCM recommends the fuel mixture be leaned for “best power” settings (see chart on page 27). This can be
done by leaning to the values in the POH, or if EGT information is available, lean the mixture by finding peak
EGT and adjusting richer to get to best power. The leanest cylinder EGT (first to peak) should be at least 50°F
rich of peak, preferably 75°F rich of peak. Since a 75 to 100°F EGT spread is normal, a single point EGT system
should be adjusted to at least 125°F rich of peak. Multi-point EGT systems should be adjusted so the cylinder
with the leanest (first to peak) EGT is 50 to 75°F rich of peak. For turbocharged engines, TIT limitations may
restrict leaning. In those cases, comply with the AFM/POH instructions.
27
TM
Lean of peak operation in the “best economy” range as shown on the “Cruise Power Settings” chart is permitted
on many models and should be used primarily for trips where extended range is desired. Lean of peak operation
requires the operator to monitor EGT closely, as power and temperature may change rapidly in response to small
changes in fuel mixture. Adjust single point EGT system’s cruise mixture 50° to 75°F lean of peak. Adjust Multipoint
EGT systems so the richest (last to peak) EGT is 25° to 50°F lean of peak. Note on the “Cruise Power
Settings” chart that lean of peak operation reduces power by up to 10% at the same RPM and manifold pressure
setting. Do not increase manifold pressure or RPM to “regain” reduced power or speed. The result is the same as
leaning from a higher power setting. You may also notice in the “Cruise Power Settings” chart that part of the
perceived fuel flow reduction operating at “best economy” comes simply because the power is reduced.
from "Continetal Guide on Engine Care." http://www.insightavionics.com/pdf%2...ontinental.pdf
High Power Cruise
High power cruise is generally defined as power settings between 65 and 74% of rated engine power. In this
range, TCM recommends the fuel mixture be leaned for “best power” settings (see chart on page 27). This can be
done by leaning to the values in the POH, or if EGT information is available, lean the mixture by finding peak
EGT and adjusting richer to get to best power. The leanest cylinder EGT (first to peak) should be at least 50°F
rich of peak, preferably 75°F rich of peak. Since a 75 to 100°F EGT spread is normal, a single point EGT system
should be adjusted to at least 125°F rich of peak. Multi-point EGT systems should be adjusted so the cylinder
with the leanest (first to peak) EGT is 50 to 75°F rich of peak. For turbocharged engines, TIT limitations may
restrict leaning. In those cases, comply with the AFM/POH instructions.
27
TM
Lean of peak operation in the “best economy” range as shown on the “Cruise Power Settings” chart is permitted
on many models and should be used primarily for trips where extended range is desired. Lean of peak operation
requires the operator to monitor EGT closely, as power and temperature may change rapidly in response to small
changes in fuel mixture. Adjust single point EGT system’s cruise mixture 50° to 75°F lean of peak. Adjust Multipoint
EGT systems so the richest (last to peak) EGT is 25° to 50°F lean of peak. Note on the “Cruise Power
Settings” chart that lean of peak operation reduces power by up to 10% at the same RPM and manifold pressure
setting. Do not increase manifold pressure or RPM to “regain” reduced power or speed. The result is the same as
leaning from a higher power setting. You may also notice in the “Cruise Power Settings” chart that part of the
perceived fuel flow reduction operating at “best economy” comes simply because the power is reduced.
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High Power Cruise
High power cruise is generally defined as power settings between 65 and 74% of rated engine power. In this
range, TCM recommends the fuel mixture be leaned for “best power” settings (see chart on page 27). This can be
done by leaning to the values in the POH, or if EGT information is available, lean the mixture by finding peak
EGT and adjusting richer to get to best power. The leanest cylinder EGT (first to peak) should be at least 50°F
rich of peak, preferably 75°F rich of peak. Since a 75 to 100°F EGT spread is normal, a single point EGT system
should be adjusted to at least 125°F rich of peak. Multi-point EGT systems should be adjusted so the cylinder
with the leanest (first to peak) EGT is 50 to 75°F rich of peak. For turbocharged engines, TIT limitations may
restrict leaning. In those cases, comply with the AFM/POH instructions.
High power cruise is generally defined as power settings between 65 and 74% of rated engine power. In this
range, TCM recommends the fuel mixture be leaned for “best power” settings (see chart on page 27). This can be
done by leaning to the values in the POH, or if EGT information is available, lean the mixture by finding peak
EGT and adjusting richer to get to best power. The leanest cylinder EGT (first to peak) should be at least 50°F
rich of peak, preferably 75°F rich of peak. Since a 75 to 100°F EGT spread is normal, a single point EGT system
should be adjusted to at least 125°F rich of peak. Multi-point EGT systems should be adjusted so the cylinder
with the leanest (first to peak) EGT is 50 to 75°F rich of peak. For turbocharged engines, TIT limitations may
restrict leaning. In those cases, comply with the AFM/POH instructions.
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LOP can be used on some engines for longest range but requires careful monitoring.
Until you have watched the effects of mixture control on a well instrumented engine Dyno with say a turbocharged engine fitted up, you will find that a bit hard to accept. Once you have done this and done some serious detonation testing and watched the effect of mixture and detonation, your mind will be changed forever.
There are a few dozen freshly enlightened pilots in the world after last weekend who would fit that bill.
Jut like ultralights 
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Gentlemen:
Please allow me some observations and explanations:
Reading this thread has thrown me into the "wayback time machine." We had dozens of these threads 15 years ago when we started teaching the APS class. The threads all were like this one: educated, critical thinkers trying to teach those who had relied for years, maybe decades, on what they were taught that was simply wrong, ...and for whatever reason could not come to grips with their misunderstandings.
When we started, we thought we would teach a one day class on engine management. There was NO WAY. It ended up taking 2˝ days to present it to make it complete and offer the student a comfortable understanding of the issues at the end of the class. That being the case there is simply no possible way to impart the information on an internet forum. We have given out reams of free information and it is still not possible to fully educate in this manner or with this bandwidth. Sorry. We wish we could. Even the online course is not quite as "complete" in this regard as the live course--at least that what those who have taken both courses tell us.
George is an aeronautical engineer. John is a retired JAL Captain who has flown everything from J-3s to WWII bombers and was a DC-3 and C-46 pilot for Air America in VN. I am a retired dentist who has spent many, many hours in the engine test stand, have flown over 75 different types of aircraft, including J-3s to the B-24 and the C-46 with the big radials. We were all WRONG about a lot when we started this.... like so many on this forum who think they know, but can't support their knowledge with data. ("We've always done it this way and never had any problems" is not proof of anything. It's nice, but it "proves" nothing.)
For George, John and me, we spent a LOT of time trying to overcome what we "knew" to be true that wasn't. It was a painful experience for all three of us to find out that, with all of our experience, what we had believed and were comfortable "knowing" about engine management for so many thousands of flight hours was simply WRONG. It became a soul-searching experience. But, in the trek toward enlightenment and many, many hours in the most advanced engine test facility in the world, we became comfortable relying on the science rather than other people's opinions. The DATA has no opinion or no ax to grind. We will tell you to this day that we do NOT want you to believe us. We want you to believe the DATA. But, to do that, one must be willing to look at the data and challenge what they believe to be true. (Remember, it requires no data or proof to "believe" something. It does require proof to KNOW something.)
George, John and I asked ourselves "How do you know when you are right?" That rather profound question has a telling answer. The only way you can know that you are right is to constantly challenge what you think you know to be true by trying to disprove your position. We have done that and continue to do that through research. As a result, we continue to learn.
The truth is, that back when we were considered "renegades" or "heretics" by the established aviation experts and the local hangar-flying know-it-alls, it was a lot more fun!!! (Our Aussie partners are finding that out!) Now that (at least in the US) we are considered mainstream, engine management experts and a source of solid, fact-based, information about piston engines, it's just not as much fun. The detractors of our teachings have gone on to worry about such things as chemtrails and the like and the forums are far less antagonistic as we have dozens of pilots and mechanics teaching others about what we and they have discovered. The same will happen Down Under--hopefully more quickly than it did here.
We have been offering a $1000us reward to anyone who could present hard, repeatable data that anything we teach is scientifically flawed or incorrect. We want to know if we are mistaken more than anyone else. So far, no one has sent us any data in an attempt to collect the reward.
Our students (of many thousands) include folks from TCM and other OEM reps as well as a number of engine builders. Not one person has ever contradicted anything we have presented. No one.
I guess no one can use an extra $1000us. It's truly a head-shaker.
Now, back to your regularly scheduled programming............
Please allow me some observations and explanations:
Reading this thread has thrown me into the "wayback time machine." We had dozens of these threads 15 years ago when we started teaching the APS class. The threads all were like this one: educated, critical thinkers trying to teach those who had relied for years, maybe decades, on what they were taught that was simply wrong, ...and for whatever reason could not come to grips with their misunderstandings.
When we started, we thought we would teach a one day class on engine management. There was NO WAY. It ended up taking 2˝ days to present it to make it complete and offer the student a comfortable understanding of the issues at the end of the class. That being the case there is simply no possible way to impart the information on an internet forum. We have given out reams of free information and it is still not possible to fully educate in this manner or with this bandwidth. Sorry. We wish we could. Even the online course is not quite as "complete" in this regard as the live course--at least that what those who have taken both courses tell us.
George is an aeronautical engineer. John is a retired JAL Captain who has flown everything from J-3s to WWII bombers and was a DC-3 and C-46 pilot for Air America in VN. I am a retired dentist who has spent many, many hours in the engine test stand, have flown over 75 different types of aircraft, including J-3s to the B-24 and the C-46 with the big radials. We were all WRONG about a lot when we started this.... like so many on this forum who think they know, but can't support their knowledge with data. ("We've always done it this way and never had any problems" is not proof of anything. It's nice, but it "proves" nothing.)
For George, John and me, we spent a LOT of time trying to overcome what we "knew" to be true that wasn't. It was a painful experience for all three of us to find out that, with all of our experience, what we had believed and were comfortable "knowing" about engine management for so many thousands of flight hours was simply WRONG. It became a soul-searching experience. But, in the trek toward enlightenment and many, many hours in the most advanced engine test facility in the world, we became comfortable relying on the science rather than other people's opinions. The DATA has no opinion or no ax to grind. We will tell you to this day that we do NOT want you to believe us. We want you to believe the DATA. But, to do that, one must be willing to look at the data and challenge what they believe to be true. (Remember, it requires no data or proof to "believe" something. It does require proof to KNOW something.)
George, John and I asked ourselves "How do you know when you are right?" That rather profound question has a telling answer. The only way you can know that you are right is to constantly challenge what you think you know to be true by trying to disprove your position. We have done that and continue to do that through research. As a result, we continue to learn.
The truth is, that back when we were considered "renegades" or "heretics" by the established aviation experts and the local hangar-flying know-it-alls, it was a lot more fun!!! (Our Aussie partners are finding that out!) Now that (at least in the US) we are considered mainstream, engine management experts and a source of solid, fact-based, information about piston engines, it's just not as much fun. The detractors of our teachings have gone on to worry about such things as chemtrails and the like and the forums are far less antagonistic as we have dozens of pilots and mechanics teaching others about what we and they have discovered. The same will happen Down Under--hopefully more quickly than it did here.
We have been offering a $1000us reward to anyone who could present hard, repeatable data that anything we teach is scientifically flawed or incorrect. We want to know if we are mistaken more than anyone else. So far, no one has sent us any data in an attempt to collect the reward.
Our students (of many thousands) include folks from TCM and other OEM reps as well as a number of engine builders. Not one person has ever contradicted anything we have presented. No one.
I guess no one can use an extra $1000us. It's truly a head-shaker.
Now, back to your regularly scheduled programming............
(Of course please ignore that if you are running a 912 IS model)
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I guess no one can use an extra $1000us. It's truly a head-shaker
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Thanks so much for jumping on here to share that post Walter. Reading it put a smile on my face but the aftertaste from yet another realization how backwards we are down under was as bitter as usual.
Curiously, a 1980 PA31-325 I've been flying &/or managing since 2007 has a manufacturer POH that includes specific instructions on operating LOP. It even includes instructions on how to achieve LOP if temp limits are reached prior to LOP.
And that's using the original single point EGT. Not that I was comfortable with not knowing if every cylinder was sufficiently LOP, so the only time I ever did it was after I took over managing it to demonstrate to the owner the benefits of LOP and explain the need for an EDM to ensure *every* cylinder is sufficiently LOP. A few months later at its annual, one EDM fitted and LOP ever since.
BTW, that EDM made its purchase price back in a single year of operation in fuel saving. If you include install costs, then that first year still made good due to an injector line failure that year that the EDM helped me to decide to return to the maintenance base instead of landing at the nearest aerodrome - and then having to deal with remote maintenance & a stranded plane & pax.
And that's using the original single point EGT. Not that I was comfortable with not knowing if every cylinder was sufficiently LOP, so the only time I ever did it was after I took over managing it to demonstrate to the owner the benefits of LOP and explain the need for an EDM to ensure *every* cylinder is sufficiently LOP. A few months later at its annual, one EDM fitted and LOP ever since.
BTW, that EDM made its purchase price back in a single year of operation in fuel saving. If you include install costs, then that first year still made good due to an injector line failure that year that the EDM helped me to decide to return to the maintenance base instead of landing at the nearest aerodrome - and then having to deal with remote maintenance & a stranded plane & pax.
Last edited by Tinstaafl; 18th Feb 2016 at 03:01.
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I'm glad you've come along Walter. I believe your company came up with an excellent product at a time when it was needed and gave the engine manufacturers a timely shove.
Perhaps you can answer a question: do you believe it is possible to teach anybody in as little as 2 mins to safely operate a carbureted engine LOP; without limitation on altitude or power, and without engine monitor, using only seat in the pants feel for the "big mixture pull"? As claimed by your Australian colleague.
Perhaps you can answer a question: do you believe it is possible to teach anybody in as little as 2 mins to safely operate a carbureted engine LOP; without limitation on altitude or power, and without engine monitor, using only seat in the pants feel for the "big mixture pull"? As claimed by your Australian colleague.
.... and whilst flying your Rotax you are wasting up to 25% of your unleaded or Avgas fuel due to the lack of altitude compensation in your twin Bing carburetor set-up! With the simplicity, also comes a manufacturer built in nufty buffer which isn't your fault but it costing you money.
The Rotax carbs do have some altitude compensation but it is a primitive mechanical system. I sometimes wonder how rich or lean the engine really is.... and then I just go back to flying.
now back to the regular LOP debate.
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**do you believe it is possible to teach anybody in as little as 2 mins to safely operate a carbureted engine LOP; without limitation on altitude or power, and without engine monitor, using only seat in the pants feel for the "big mixture pull"? As claimed by your Australian colleague.**
Absolutely. I have done that on multiple occasions. (I taught my Aussie colleague!) It takes about 15 seconds if injected, 2 minutes if carbureted. How you might ask?
Carbed engines have notoriously poor F:A ratios and as a result many think it impossible to run them LOP. Not so. It is NOT imbalanced air--it is imbalanced fuel. The key is finding the optimal IAT using carb heat to get the fuel which has been atomized to become vaporized (I am hesitant to spend hours typing what can be demonstrated in under a minute in the airplane). Once this happens, the F:A ratios will be well balanced. I have accomplished this on radials as well as flat engines. I've personally accomplished this on most Cessnas, Pipers and many other carbed engines. Use the minimal carb heat to get the lowest DIFF number and you're good to go.
It only requires a single-probe EGT and a carb temp gauge.
It is important to appreciate that IF the F:A ratios are balanced all cylinders will be at very nearly the same mixture and the engine will run smoothly LOP. (And better ROP) This is how the engine is SUPPOSED to be. It does not matter how the fuel is delivered to the cylinders. Injected engines have this accomplished by having balanced nozzles (like GAMIjectors), while carbed engines use optimal vaporization to accomplish this. This is not my discovery. About 15 years ago, I read it in the small print (6pt. type footnote) of a 1935 engine operation manual; tried it on various carbed engines and found it to work quite nicely.
Consider this: If the engine is "conforming"--having balance F:A ratios, healthy ignition, no induction leaks and is being operated on the proper fuel--it will run smoothly across the entire mixture range, including LOP. Non-conforming engines will "seem" to run smoothly ROP because the differences in mixture, etc, between the cylinders is masked by the fact that the HP curve is so flat in the commonly useable range of ROP mixtures. Your Mark One calibrated butt doesn't feel the differences when ROP. It does when LOP.
SO..... if you run ROP, you need an engine monitor MUCH more than if you run LOP! If you have a conformity problem LOP, the engine will let you know by running rough. Not so if ROP.
WAIT! You did ask if ANYBODY could learn this in under 2 min.? Hm???????? I'd say "almost" anybody. They have to be willing to challenge what they know that isn't so. <g>
Absolutely. I have done that on multiple occasions. (I taught my Aussie colleague!) It takes about 15 seconds if injected, 2 minutes if carbureted. How you might ask?
Carbed engines have notoriously poor F:A ratios and as a result many think it impossible to run them LOP. Not so. It is NOT imbalanced air--it is imbalanced fuel. The key is finding the optimal IAT using carb heat to get the fuel which has been atomized to become vaporized (I am hesitant to spend hours typing what can be demonstrated in under a minute in the airplane). Once this happens, the F:A ratios will be well balanced. I have accomplished this on radials as well as flat engines. I've personally accomplished this on most Cessnas, Pipers and many other carbed engines. Use the minimal carb heat to get the lowest DIFF number and you're good to go.
It only requires a single-probe EGT and a carb temp gauge.
It is important to appreciate that IF the F:A ratios are balanced all cylinders will be at very nearly the same mixture and the engine will run smoothly LOP. (And better ROP) This is how the engine is SUPPOSED to be. It does not matter how the fuel is delivered to the cylinders. Injected engines have this accomplished by having balanced nozzles (like GAMIjectors), while carbed engines use optimal vaporization to accomplish this. This is not my discovery. About 15 years ago, I read it in the small print (6pt. type footnote) of a 1935 engine operation manual; tried it on various carbed engines and found it to work quite nicely.
Consider this: If the engine is "conforming"--having balance F:A ratios, healthy ignition, no induction leaks and is being operated on the proper fuel--it will run smoothly across the entire mixture range, including LOP. Non-conforming engines will "seem" to run smoothly ROP because the differences in mixture, etc, between the cylinders is masked by the fact that the HP curve is so flat in the commonly useable range of ROP mixtures. Your Mark One calibrated butt doesn't feel the differences when ROP. It does when LOP.
SO..... if you run ROP, you need an engine monitor MUCH more than if you run LOP! If you have a conformity problem LOP, the engine will let you know by running rough. Not so if ROP.
WAIT! You did ask if ANYBODY could learn this in under 2 min.? Hm???????? I'd say "almost" anybody. They have to be willing to challenge what they know that isn't so. <g>
Last edited by Walter Atkinson; 17th Feb 2016 at 16:51. Reason: spelling and such... <g>
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The Rotax carbs do have some altitude compensation but it is a primitive mechanical system. I sometimes wonder how rich or lean the engine really is.... and then I just go back to flying.
As for helping get correct air fuel ratio and vapourisation, the 912 ULS operating manual suggest the best carby air temp be kept at 21 deg C. (going from memory)
Last edited by Ultralights; 17th Feb 2016 at 21:47.