Another Leaning Thread...

J

Joseph Banning

Filing Flight Plan
Joined
Aug 22, 2017
Messages
9
Display Name
Display name:
JBanning
Hello to the POA community. I am newly minted private pilot as of November 2016 and fly a Cessna 150M and a Cherokee 140 out of 58M in Cecil county MD.

With the introduction out of the way, I am posting another mixture leaning thread. I realize from searching that there is plenty of information on how to lean piston engines with and without fuel injection. I understand LOP, ROP, leaning by EGT, leaning by "stumbling engine" and what that does to CHT as well as how that can affect the health of my engine.

There is one thing that keeps popping up in my head and I can't seem to find an answer based in real world experience. What happens if you run LOP in a carbureted engine, and just ignore the "roughness" of the engine? Will it damage my engine mount, air-frame, accessories, crank shaft, case bearings, etc... from excessive vibration?

Where is this coming from? I have a UBG16 monitor in my 140 and I have noticed that the engine starts running a little rough "stumbling" before my hottest EGT peaks. A few times, I have just continued to lean the mixture and saw the RPM dropping, by about 100 RPM. I got a little nervous because the combination of RPM drop, and roughness of the engine so I am not even sure if my EGT peaked or not - I enriched the mixture until I had a smooth running engine and called it good... However, thinking back on it... the RPM drop was normal, the roughness was just from airflow imbalances that are normal for these engines and it wasn't THAT rough... Also... I may be imagining this, but I seem to remember that as the RPM dropped lower with leaning, the engine actually started to run a bit smoother.

So I wonder, what would be the harm in running LOP and just allowing the engine to have some minor stumble?

Thanks!

- Joe
 
A couple er three things. 1) Minor stumbling = misfire = loss of efficiency 2) added vibration = added wear on engine mounts, gauges (yes, the jewels in the gauge movements develop flat spots over time or so I've been told when the repair guys say replace it), all rotating components and accessories 3) always lean forward.

Added note: misfires will increase EGT as unburnt fuel exits the cylinder, the fuel burns in the exhaust pipe.

Other added note: welcome to POA
 
Hey, another local. Welcome to PoA.
 
For Odin's sake, if you're leaning to try and save gas in those airplanes get out of aviation! You're flying the least expensive airframes outside of the experimental world. Lean until the engine stumbles you loose RPM, then enrichen until it runs smooth. That is all.
 
Joe,

Welcome to POA.

As others have already stated, lean until you get that rough running then add a bit to smooth it out. I don't even use my JPI anymore to lean, it's by feel. I think my EGT's run about 1300.

I have my maintenance done at 58M, Cecil Aero. I actually think we met while I was waiting for my rental car at the terminal in November 2016, my annual time. I fly the white and red Beech Sundowner.
 
weilke said:
Lean forward !
Click to expand...

Huh?

Clark1961 said:
A couple er three things. 1) Minor stumbling = misfire = loss of efficiency 2) added vibration = added wear on engine mounts, gauges (yes, the jewels in the gauge movements develop flat spots over time or so I've been told when the repair guys say replace it), all rotating components and accessories 3) always lean forward.

Added note: misfires will increase EGT as unburnt fuel exits the cylinder, the fuel burns in the exhaust pipe.

Other added note: welcome to POA
Click to expand...

Stumbling from misfiring during leaning is not in line with what I have read and come believe about these engines. I thought the roughness was from the fact that as temperature approaches peak EGT, the amount of power produced by a particular cylinder becomes much more sensitive to variations in either airflow, fuel flow, fuel mixture or some combination therein. When operating on the rich side of peak, this sensitivity is diminished. With our old carbureted, horizontally opposed engines, the induction system lack precision in the quantity of fuel/air that is delivered between each cylinder. Therefore as temperature approaches peak EGT, the power produced by each cylinder diverges. I thought it was these unequal power pulses that cause roughness.

I concur that logic dictates that added vibration would increase wear on the listed components. I just wonder if the roughness I am feeling is any worse than the background vibration which already exists, or is it just different and no more harmful?

steingar said:
For Odin's sake, if you're leaning to try and save gas in those airplanes get out of aviation! You're flying the least expensive airframes outside of the experimental world. Lean until the engine stumbles you loose RPM, then enrichen until it runs smooth. That is all.
Click to expand...

I am a scientist by profession and it is my tendency to thinker deeper into topics that may seem simple on the surface. While I am familiar with this simple leaning practice, and use it most every time I fly in a circumstance appropriate for leaning, I still like to think about obtaining better efficiency - fully knowing that the 140 is an inefficient air frame. I would suggest that if dogma and Odin suit you, then do not participate in technical discussions probing beyond dogma. Furthermore, gathering information on a topic from a large group of experienced individuals is a lot cheaper and safer than repeating experiments that perhaps others have already done.
 
Well for one, it's going to make temps skyrocket and ultimately damage the engine.

As Steingar said, there's no need to even try LOP operation in a 150 or 140. Lean them both 50deg ROP and you'll burn what, 6-8GPH at most?
 
Last edited:
GMascelli said:
Joe,

Welcome to POA.

As others have already stated, lean until you get that rough running then add a bit to smooth it out. I don't even use my JPI anymore to lean, it's by feel. I think my EGT's run about 1300.

I have my maintenance done at 58M, Cecil Aero. I actually think we met while I was waiting for my rental car at the terminal in November 2016, my annual time. I fly the white and red Beech Sundowner.
Click to expand...

I do remember meeting you, and thanks!

I understand the common leaning practice, I just cant help but thinking about other possibilities.
 
Joseph Banning said:
Huh?



Stumbling from misfiring during leaning is not in line with what I have read and come believe about these engines. I thought the roughness was from the fact that as temperature approaches peak EGT, the amount of power produced by a particular cylinder becomes much more sensitive to variations in either airflow, fuel flow, fuel mixture or some combination therein. When operating on the rich side of peak, this sensitivity is diminished. With our old carbureted, horizontally opposed engines, the induction system lack precision in the quantity of fuel/air that is delivered between each cylinder. Therefore as temperature approaches peak EGT, the power produced by each cylinder diverges. I thought it was these unequal power pulses that cause roughness.

I concur that logic dictates that added vibration would increase wear on the listed components. I just wonder if the roughness I am feeling is any worse than the background vibration which already exists, or is it just different and no more harmful?



I am a scientist by profession and it is my tendency to thinker deeper into topics that may seem simple on the surface. While I am familiar with this simple leaning practice, and use it most every time I fly in a circumstance appropriate for leaning, I still like to think about obtaining better efficiency - fully knowing that the 140 is an inefficient air frame. I would suggest that if dogma and Odin suit you, then do not participate in technical discussions probing beyond dogma. Furthermore, gathering information on a topic from a large group of experienced individuals is a lot cheaper and safer than repeating experiments that perhaps others have already done.
Click to expand...
Leaning forward is an old joke on this board.

Maybe think of a misfire as incomplete combustion. Any way you want to think about it unburnt fuel is one result and that is a loss of efficiency. The whole point of leaning is to maximize power and efficiency so any misfire is bad.
 
Joseph Banning said:
I am a scientist by profession and it is my tendency to thinker deeper into topics that may seem simple on the surface. While I am familiar with this simple leaning practice, and use it most every time I fly in a circumstance appropriate for leaning, I still like to think about obtaining better efficiency - fully knowing that the 140 is an inefficient air frame. I would suggest that if dogma and Odin suit you, then do not participate in technical discussions probing beyond dogma. Furthermore, gathering information on a topic from a large group of experienced individuals is a lot cheaper and safer than repeating experiments that perhaps others have already done.
Click to expand...

Fellow scientist. If you want more efficiency get a Mooney. Same gas, lots more speed. By the way, if you think leaning is difficult on your airframe, try doing it with a constant speed propellor.

Talking to my mechanic, I complained that the mixture and flap knobs looked sufficiently similar to mistake one for the other (which I have almost done on occasion). He suggested I paint the mixture knob orange.
 
steingar said:
Fellow scientist. If you want more efficiency get a Mooney. Same gas, lots more speed. By the way, if you think leaning is difficult on your airframe, try doing it with a constant speed propellor.

Talking to my mechanic, I complained that the mixture and flap knobs looked sufficiently similar to mistake one for the other (which I have almost done on occasion). He suggested I paint the mixture knob orange.
Click to expand...

I can see how that would cause problems if you have electric flaps...

I am ok with the speed and efficiency that I get out of my 140. I bought it because it has a waas gps, stec 30 autopilot w/altitude hold and a lot of other goodies that really do not belong in a 140. But because it is a 140, the price could not get that high and I took advantage of someone elses mistake. I plan to use it for my instrument rating and gaining experience with instrument flying. It will also take me and my +1 on some fun trips. In the 90 or so hours that I have flown since November, it has all been with +1 person and not more than 75-150 miles for breakfast, dinner or the occasional day trip to the beach. With the "back seats" removed from the 140, it is awesome at this mission. Perhaps occasionally I will go further and wish for more speed, but right now - it is a sweet spot.

The idea is to save up for something or build something slippery and experimental while having fun and learning with the 140. And one way i get my kicks, is to tinker and try and learn something new... hence this thread...
 
Got it. The wisdom you got from me was learned on a Cherokee 140 that I flew for the better part of a decade. I traded mine for a Mooney that probably doesn't have the panel you've got in the 140. One good thing, you'll have plenty of time to run all those approaches...
 
Michael has shared some wisdom. My comments come from a couple sources. I learned to fly carbed 172s from an airport with a ~5,700' ground elevation. Leaning for best power was completed prior to every flight. We never messed around with roughness. Find the edge off roughness then give it lots of gas. The schools engines gave good service lives according to the logs.

Then I bought a plane with a TSIO-360. That's a turbocharged, fuel injected engine. I've converted the engine to used a different fuel system (new pump, new injectors) and flow balanced cylinders. The engine went from being impossible to run LOP to being able to be leaned until it just quits.

Any roughness that develops during leaning means a cylinder is producing significantly less power than the other cylinders. That means the cylinder likely has incomplete combustion and one direct result of continued operation at that mixture setting is that EGT will be quite high. I have the advantage of a temperature probe at the turbocharger inlet so I can see individual EGTs plus the mixture EGT.
 
Fuel injection and flow balanced cylinders will be a must in my next plane.
 
Hah, I just searched that and read it! Why on earth did he tell his buddy to lean forward? Was it for the sake of bracing for impact into the barn?
 
Some mysteries are shrouded in the mists of time. That particular mystery is just shrouded.
 
Welcome,I'd rather spend money on fuel,rather than an engine overhaul,keep the engine cool.
 
You must log in or register to reply here.
Back
Top