Obsessed With EGT
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- čas přidán 10. 02. 2023
- Many pilots have been taught -- and many POHs recommend -- leaning by reference to EGT, e.g. 50 degrees F rich of peak (ROP) or 25 degrees F lean of peak (LOP). Most digital engine monitors have a fancy "lean-find mode" designed to assist pilots in doing so. In this webinar, engine expert Mike Busch explains why this is a bad practice that can adversely affect your engine's longevity. He explains why it's better for your engine's health to lean by reference to CHT and fuel flow (FF). Mike believes that EGT is great for troubleshooting but not for leaning, and he explains why. Savvy Aviation offers Professional Maintenance Services to owners of General Aviation aircraft, such as: SavvyMx (Professional Maintenance Management), SavvyQA (Expert Consulting), SavvyPrebuy, SavvyAnalysis (Engine Data Analysis) and Breakdown Assistance. Savvy also publishes a monthly newsletter with lots of interesting information for the general aviation enthusiast; subscribe to it at www.savvyaviation.com or text the word "Savvy" to 33777. This webinar was hosted by the Experimental Aircraft Association (EAA).
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This kind of information, derived from the chemistry upwards, with Mike's huge knowledge and experience, and his real-world TBO experience, is absolute gold. I've seen and heard so much wrong and downright dangerous and contradictory information on how to run these engines. I'm so glad there is this beacon of grounded knowledge with Mike.
Thank you!
I'm glad to see Mike Busch continue these topics with fuel management and aircraft engines. I was a big follower of John Deakin's Pelican's Perch articles in AvWeb back in the early 2000's. John wrote at length about the ROP/LOP theories, among others, along with the his famous acronym WOTLOPSOP...Wide Open Throttle Lean of Peak Standard Operating Procedures. He, too, work closely with George Braly to confirm his theories. All good stuff!
The problem with not using EGT is sometimes in rental aircraft, which the many of us who are not fortunate to own an airplane only have the EGT gauge in the aircraft. The other option would be how I learned way back in the early 80s to lean until the engine started to drop off RPM And fly approximately 25 to 50 RPM below maximum RPM for the throttle setting. It’s some cases leaving the throttle full and adjusting cruise power/ rpm with the mixture.
Loved it!
Bravo Mike!
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Thanks Mike, always listening from LOO !
Your explanation of LOP operation is very interesting.
It makes sense, Deisel engines have no throttle, the control of power is solely determined by fuel metering.
I works on turbines, it works on deisels, why wouldn't it apply to petrol engines?
I guess the early petrol engines had throttles because it was easy, and it stuck.
The throttle is useful because:
1) It allows for power modulation at lower power settings, without roughness, misfire, and risk of engine stall.
2) It simplifies non-computer controlled (i.e. mechanical) power modulation, because wide-open position produces max power. Conversely, max power is produced below full-rich mixture. Also, there is a wide range of rich mixtures that results in very small changes of power.
I always pull to rough running. They always ask what was that. I said we’re out of fuel 😂
Once I learned where my peak and lean of peak, once I am at 22/22 I go straight to approximately the gallons per hour I know has my EGT & CHT where I want it. Low load on the engine in cruise and only loose 10 mph , 125 mph instead of 135.
The engineers of the 50s and 60s should have known about leaning as Lindbergh knew about it in the 30s.
@@brettdavies-young7102 I agree. Hopefully, people like the folks at GAMI and Mike are slowly dispelling the myths and newer engines like Rotax simply build it into the automation so pilots no longer need to be in the loop doing the wrong thing.
They did know. All this simplification to our detriment came when lawyers started help write POHs. Take the APS course at Ada even if just the online version. It is so worth it. Lots of the info comes from the WW2 data tables and manuals. The B-17 engineers used all kinds of good stuff to determine exact mixture settings for the pilots.
When I get to my cruise altitude in my Cherokee Six I set the RPM and fuel flow on my IO-540K1A5 in accordance with the curves in the Lycoming engine manual. The curves I use are on page 3-34 of the Lycoming Operator's Manual for the O-540 and IO-540 (Part No. 60297-10). After setting the RPM to (usually) 2400, I use the big pull and quickly set the corresponding fuel flow. The throttle is always at maximum until I get to pattern altitude at the destination airport. This works every time.
I have a Garmin G3X with "Lean Assist" and wonder if it would have the same adverse effects as the "Lean Find"?
Great video Mike! You mentioned that you fly with the throttle wide open and once LOP, use mixture lever to set the desired % power provided CHTs don’t go above 400. I’m curious, are the following two techniques equivalent or is one better than the other from internal cylinder pressure perspective?
1. First set MP to achieve the desired % power (say 75%), then keep leaning until we are lean of peak; as soon as we are in LOP regiment, % power will start dropping so we can stop right at 75% provided CHTs < 400.
OR
2. Keep the throttle wide open, keep leaning until we achieve 75% power and stop right there provided CHTs < 400.
In both cases we achieve 75% power, and based on the formula you shared, both should yield exactly the same results in terms of fuel flow since they are flown LOP and power is proportional to fuel flow. But are both cases equivalent in terms of CHTs?
My second question is what do you do when you need to slow down, say during an instrument approach? Do you pull back the throttle and mixture together to keep fuel-to-air ratio constant? (since reducing throttle enriches the mixture) Or, do you simply keep the mixture as is and reduce throttle far enough (below 60% power) where the suddenly slightly richer mixture doesn’t matter? (since the red box ceases to exist).
Number don't mean much, unless it's a turbo inlet temp egt probe, it's more about the rate of rise and fall between each cylinder and one another
I like this much better than some of the propaganda of the deciples of the church of LOP, thanks Mike. It's really almost tragic how people fear the red box or purple box, that doesn't even exist below 75% power in a IO360 e.g., you don't get CHT that high, didn't see more than 360° in cruise. Above that the best approach is full rich, because you really don't get outside the red box with less fuelflow. NA engines in cruise usually aren't operated above 75%. If you lean from 70% power until you arrive at 65% power, you never go through the red box and are well LOP. It's really very simple and over amplified.
Although I am very much in agreement with what Mike has to say, I am not sure that I fully agree with throwing away EGT as a primary tool for leaning as it obviously responds much faster than cylinder head temperatures. I completely agree that it isn't worth spending time in the red zone to know exactly how lean of peak one is. But thinking that if after making the big pull exhaust temperatures are more than say 50 or 100 degrees higher than they were comfortably rich of peak (at a 70% power fast cruise I would guess this is 100 to 200 degrees lower than peak), then there is a good chance that cylinder head temperatures will be creeping up over a few minutes too.
So after Cirrus discovered it was their recommended slow transition from ROP to LOP was causing the fine wire plug insulators to crack, what did they do? Change the guidance on how to lean, change the plug manufacturer or something else?
I am aware that Cirrus issued a service bulletin recommending the Champion fine wire plugs be removed from service. All new airplanes from that point on shipped with Tempest fine wire plugs. I assume this was in response to the cracked insulators on the Champions.
I am not aware that Cirrus changed their recommended leaning procedure. They might have, but I'm not aware of it. -- MB
Thank you for your very informative talk about engine leaning and LOP operation. I have an aeroplane with a 285 hp radial, supercharged. I use it for aerobatics at high power settings. Do you recommend the same LOP operation principles as in your webinar?
Quick question... Youre saying 75% 65% power... Does that mean the best power ? Cus i believe when we for example set 75% and then go lean of peak basicly the power gonna go down..
Or its the other way, go 85% and lean to known 75% power referring to fuel flow ?
Wonderful educational thanks a bunch Mike... Suck squeeze bang Blow. Who new it's this complex and fun 😂😂 so to add to the cracking spark plugs.. what about climbing after lop would cause a very bad situation buy putting pilots in the box for extended period of time until the pilot gets to the mixture after they stabilize at cruise... ?!?!? Just a thought of maybe picking a different power setting where one is constantly changing altitude.... But would decrease climb performance. But would raise pilot work load in dense traffic.. so that's why I like injection and rotax they don't have to worry about the big red stick lol
Coming from the automotive world I was surprised there isn’t a wide band oxygen sensor to run an air/fuel instrument. If we had these, it would the best way to adjust fuel mixture. Hopefully once we transition from 100LL to UL we’ll see air/fuel instruments too
I agree. O2 sensors don’t like lead so they aren’t an option with the current archaic aviation engines and fuels. Aviation propulsion is at least 50 years behind the technology curve sadly.
In automotive applications, is catalytic converter needed to have the after- before O2 readings to get a measure of unburnt fuel?
Simple is reliable........the more you try to make automotive engine mods to aircraft engines the less reliable they are as aircraft engines
@@BrianOgilvie79 Modern auto engines are vastly more reliable than were their much simpler predecessors. A modern airplane engine will be more reliable than current 70 year old technology engines. Absolutely no doubt about it.
@@rossrobinson7943 no, the sensor before the converter measures mixture and the one after the converter measures the efficiency of the converter
As Mike says @ 39:00. Run 65% power and run peak if you want. Continental also says this. If your exhaust is gray, perfect, if black, too rich.
It wasn’t until an 1+ 20 minutes in, he said he ran the throttle all the way in at full. Then adjust the mixture for fuel flow and manifold pressure. I don’t think he gave us the formula in this entire monologue. He told is what he does, but not how to do it unless of course I missed that part.
I still wanna know why in the POH of the Cessna 172R, it said continuous engine operation at LOP prohibited. This is setting in boldface.
Maybe it's just because you could shut down the engine if you go to lean?
i find the subject of leaning and fuel flow fascinating..However on one of the videos on youtube this pilot leaned his aircraft using fuel flow which did not make sense to me.On a very hot day or a very cold day leaning using fuel flow might put him smack in the red box..Am i thinking correctly?
1:07:25 he answers this question
Modern car engines last a long time so I suspect electronic engine controls and their algorithms will not reduce the life of an engine. Now, auto engines have control over fuel mixture as well as spark timing so they can avoid areas of operation that are sub optimal whereas only Rotax does that in the aviation world as far as I know today.
Main reason they last so long is they don't operate at high power levels for long periods. A car cruising at 80mph down the highway might be using 30hp to maintain that speed. Whereas a plane is cruising at 60-75% power for nearly the entirety of the flight.
@SJ Aviation And yet both of the modern Honda and Suzuki based aeromotors are just as reliable, if not more so.
@@amtank because they are built for that type of operation, not automotive.
@@amtank Based on what data?
@@sjaviationmodern automotive engines last much longer than the automotive engines from the era most aero engines were designed. Since they have the see the same usage, it's probably accurate that the modern electronic engine controls are contributing to longevity.
I wish such detailed testing and analysis was published concerning the ubiquitous Rotax 912 (carb'd), where mixture can only be adjusted on the ground. There are far too many--usually contradictory--opinions, and far too little real analysis. I want a "George and Mike talk Rotax" video. ;)
There is a lean tool that can be added to the rotax 912 carbs with adjustment in flight. I have fitted one to my aircraft with good success. It’s experimental only tho
Great seminar, as usual.
In the chemistry part of the lesson, some folks may get confused about Octane as a molecule vs Octane rating. The octane molecule has 18 structural isomers, all of which have the same C8-H18 atomic composition. One was chosen as the octane rating reference octane isomer: 2.2.4 Trimethyl Pentane (iso-octane). Gasoline will contain other octane isomers, which have different octane numbers, and flame speeds.
The curious among you now have search terms that will allow you to get the full picture!
In a vehicle that relies on pilot adjustable mixture control in every phase of its operation, where range and payload and maximum performance are required on every flight. As well as safety and power-plant longevity.
Why haven't there been AFR (Air Fuel Ratio) Sensors equipped since the mid-80s?
Its ridiculous.
Some say its due to Lead fouling. But spark plugs suffer also, and the fix is simple.
Tbh, by the mid-90s ALL aircraft should have been retrofitted with modern EFI instead of the ancient, ice prone carburetor or vapor-lock susceptible non-return style caveman injection systems.
MoTeC, ProEFI, Megasquirt, MSD, Holley. Why aren't there aftermarket or OEM solutions for certified AC?
i was wondering the same thing, wouldnt an automotive aftermarked AFR Sensor save the hassle of finding peak EGT and get you an exact AFR?
i found your point about lead fouling very interesting and searched for lambda sensor and lead fuel.
some numbers for automotive Wikipedia said were: 160,000 km normal, 24,000 km with leaded fuel so it shortens their life by 5/6
Sunoco Race Fuels has this to say:
"Many racers using a leaded fuel in an oxygen sensor application are able to use the sensor only for tuning purposes and then remove it. This ensures a much longer usable life for the sensor."
dont know how worth it is, FAA wants to phase out leaded fuels by 2030 so then it would be easier
Yup. Throw an 02 gauge in at least. If it goes bad oh well who cares change it out. I ran a 800hp car on 110 leaded fuel for 35k miles. Never once had a sensor go bad. I might just throw them in my experimental planes and find out
Why are max CHTs different for different manufacturers?
Lycoming uses sodium-filled exhaust valve, which tend to tolerate higher temperatures.
Lycoming CHT's tend to run about 20°F hotter than Continental CHT's, largely because Lycoming sodium filled exhaust valves are more efficient at transferring heat to the cylinder head than Continental's solid stem valves.
Lycoming's red line is about 40°F hotter (500°F versus 460°F). I believe the biggest factor is that the much more robust head-to-barrel junction of Lycoming cylinders can tolerate more heat before it starts to come apart. -- MB
I have a degree chemistry and am published in organic chemistry… loving this lol. I ended up wasting all that great knowledge on being an artist, opps I mean physician. 😂😂😂
heat is waste, expansion is what moves us. Lose >70% of the gasoline's energy to heat unfortunately.
Slide 28 is incorrect. The excess fuel doesn't act as a refrigerant, it simply isn't burned due to lack of oxygen, and thus doesn't get to release its energy. Temps drop LOP due to additional air mass the fuel energy must heat
Not sure it is incorrect. If it cools cht, than it is correct isn't it? I don't read too much into the "refrigerant " term
It's not incorrect, it really is evaporative cooling like sweat. But faster.
@@TheBarzook except it isn't. Evaporative cooling makes roughly a 14F degree difference to the precombustion mixture temperature from ROP to LOP
Andrew Lynch ….. If the excess fuel didn’t cool the EGT, and only stopped producing heat, then EGT would peak and hold. Since the EGT does drop as the mixture gets too rich, it’s obvious that fuel is cooling the gas temp. Your statement that the mixture is cooler LOP because there’s more air to heat than fuel to make that heat is the corollary of the ROP situation. At ROP, air is limiting, so any additional fuel simply adds something that must be heated by the maximal fuel burn/reaction/heat production. Maybe, as you say most of the actual evaporative cooling happens in the intake manifold, but we aren’t measuring that, we are only measuring on the CHT or EGT.
@@jimrankin2583 recommend reading about adiabatic flame temperatures in relation to fuel mixture
EGT is really set them to the 1350-1450 range and enjoy a long lasting engine that’s happy. This guy saying 1600* is ok is nuts.
Does not bother me
The POH’S written in the 70’s reminds me of the owners manual of modern cars telling us that the transmission fluid does not need to be replaced since it is a lifetime fluid…Even certain dealers in the service dept tell us that..I find that ammusing.
I so would love to listen to Mike, but oh man, he certainly says hmmm and uhmm four times more than any other word. I Can't listen more than 2 minutes at the time. How do others deal with that?
Playback speed to 2x..
First comment! 🤪
It’s so strange how GA obsesses over the tuning of early 20th century engine technology, instead of implementing modern engine electronics that do a better and safer job than a human could ever do. It’s morally irresponsible. Then you realize money is the barrier. Free market capitalism - a great system we made for ourselves. And no, you’re wrong, necessity is the mother of invention.