The A&P response above is a brilliantly concise review of LOP. The difference in cylinders on the leaning curve is the main issue trying to run LOP and why it may not be possible. Adding partial carb heat may help to even out the cylinders by changing how the air is flowing but not a guarantee. I don’t want to encourage everyone with a carburetor to run LOP but if you have a good engine monitor and can see everything the engine is doing then you can determine if it’s possible. The person I bought my 1968 235 only ran ROP and at the last annual had a bit of carbon build up in a few cylinders losing some compression. So you have to choose what you think is best for your engine. As long as my engine runs smoothly and CHTs are low and consistent then I’m happy running LOP. I’ll let you know at my next annual or sooner if any problems arise.
I am having an engine monitor, the JPI EDI 900 installed in my Piper 235 next week. I have read a lot on LOP operation, and I've only seen 2 potential problems mentioned as you state. I also figure if the engine runs smooth and CHT are within normal limits, can't see any other problems. I will say I have a Peterson STC for mogas, and they clearly state no LOP operations on mogas. I wonder if it has not been tested and that's the reason for the caution. I will admit I'm the guy who constantly asks "why" in life, which can be annoying to some people. I don't mind being proven wrong. I just want to understand the logic behind the recommendation. I actually understand combustion pretty well and have had a few years of college chemistry so I understand the differences between avgas and mogas, tetraethyl lead, octane, etc.
Hey, that Corvette is fuel injected I think? Should we try LOP and see how she does?
My Corvette is a 69 and I took it out for a minute to warm it up a few days ago. There is still snow on the ground so it went back in the shop.
Old school A&P Thoughts: The limiting factor to leaning an engine is 400 degrees. This is the temperature when nasty things happen to pistons, rings, and cylinders. Detonation occures and all kinds of maintenance come up. If your engine is non-turbocharged, non fuel injected,it by design was constructed to not run at high altitudes. Running lean to peak at mid range altitudes then is for reducing fuel consumption, at the potential detriment of harm to overheated cylinders. Running an engine at 6-9 thousand feet and not leaning precisely will not get to the 400 degree temperature. Overheating an engine on climb out or decent is a real possiblity. A $500 cylinder head temperture guage (6 wire for a 6 cycliner engine) probably gives you the extra insurance you want, to not burn up an engine.
Thank you for your thoughts. I've seen the graphs about how fast the strength of aluminum fall off at temps above 400 F, it's scary. I see Shanff is at 376 F, I will be interested to see my temps with new monitor installed. My CFI is not a fan of LOP in a carbureted engine.
Here is my opinion on CFI's. And no disrespect meant to any CFI. Most CFI's spend their time circling the pattern or doing stalls 15 miles from the home airport. Other than an occasional cross country for training purposes they don't get much practice on long cross countries, especially when they have to pay the bills. I would trust a long cross country flying pilot / owners opinion on things related to maintenance, efficiency, dollars long before I would a CFI. Of course, there are really good CFI's that actually have flying experience and yours may be one of them.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Comments on LOP operation for Lycoming normally aspirated engines:
Some Lycoming carbureted engines particularly the O-360 series can be run LOP. We do it all the time in our Cherokee 180 and we have had the engine borescoped at annuals to make sure it is not being damaged.
You will need to fully instrument the engine which means both EGT and CHT on all cylinders are being monitored in real time. Also, a fuel flow (FF) sensor should be part of the package as FF is a key factor to be monitored.
Part of your engine monitoring program is capturing the engine data and downloading it to a PC so that you can look at the data post flight. Not only are you looking for normal operation, the graphic representation may uncover a problem with your engine or with your methods of operation. I cannot stress how import it is to review the recorded engine data and in item 6 below a way is provided to view this on your PC for free.
In our engine (O-360) 10GPH or higher is typical for ROP operation. During LOP operation depending on altitude (higher more efficient) and RPM, the fuel burn will range between 7.5 to 8.5 GPH. During a long cross country this can translate into a considerable savings.
I am not going to tell you how to run LOP because the technique, although not too complicated, is something that needs adequate description and is covered in several articles available on the web. Once you understand the process you can do it without much trouble. Also note that you may need to add carburetor heat during the leaning process and in our case this makes the difference between a rough or smooth running engine. The following link has the best overall description of LOP operation and will answer many questions about it: https://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning-198162-1.html
If this link doesn't work Google Savvy aviator #59 .
I am a fan of Mike Busch. His articles and books on how to operate and maintain GA piston engines are very good. I would recommend becoming a subscriber to his monthly newsletter (free). Also if you become a member, you can upload your engine monitoring data to his website and view it for free. When you start looking at your engine data, it will open your eyes as to what is really going on "under the hood." Also, he provides many articles on the theory and operation of LOP and what is going on inside your engine. His website is: https://www.savvyaviation.com/
Note: The website provides different membership options that are fee based, but the basic level is free.
Yes, thank to all. There is a lot of good information here. Scott, my CFI is an interesting guy. He has about 1800 hours and was a crop duster. My impression is not much scares him! He does seem to know quite a bit about planes and he hangs around the hangers working on planes and helping out the A and P mechanic. I think they are good friends. Methinks it is a good idea to keep my mouth shut and not voice any opinions yet. As we progress along I will ask some more about his opinions and how he came to his conclusions. He's a great CFI, I must say.
I recently got 2 quotes for my airplane insurance. They differ by about 30 percent which surprised me. Is it appropriate to ask questions about insurance on this forum?
That will be helpful, I'll look at both policies tomorrow. I suppose there is a page here that gives general advice for what kind of insurance I should be carrying. I don't know how common it is to own a plane while being trained. Also the plane is having stuff added to it and the value is increasing but how an I going to evaluate the additional insurance needs? There is no loan on the plane.
Today I went to visit my Piper 235 nicknamed the "Rice Rocket" A and P showed me a tangled web of old wires removed, cable for the RPM gauge, rusty and broken fuel senders, etc. He put in all new lines while the tanks were out. He got a good look at the spars? I thinks it's the spars, no corrosion. He thinks we have removed 30 lbs.! I am looking forward to seeing the JPI EDM 900 finished, The panel already looks very different and much less cluttered.
The A and P also thinks my original autopilot will work now. I'm not sure how sophisticated it is, but it's a start I guess.
One day at a time. Get your bird in the air and then continue restoring it. Let me know if you want to talk to Sky Smith. I'll get you his contact info.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Between the annual and the terrible weather here, I haven't been able to fly much, but yes, I am hoping to get the plane up a lot this spring and have my PPL by Summer. Today is a good day for me to talk to Sky Smith as I am at the office doing paperwork. thank you
Yes, the nickname started because many years ago I worked with an electrical crew. I was the biggest guy on the jobsite, usually, so when there was a tough "wire pull" they would come get me and take me away from what I was doing. I used to grumble when they asked me and they thought it sounded like Lurch on the Adams Family. I guess he was 6'6" where I am 6'3", but close enough.
It could have been worse I suppose, they could have called me called Uncle Fester....
I've got a mogas question. I've been running mogas most of the last 100 hours. My mechanic showed me some damage to a Piper Cherokee 140 engine that was running mogas. The valves looked damaged from valve recession, a lot of signs of excessive heat, discolored heads etc. The engine needs an overhaul after 400 hours. He suggested I run 50/50 avgas and mogas.
Of course I have no idea if the other plane was running lean or there was some other issue. I did run the 50/50 mix last tanks and the engine monitor showed about 100 degrees less on the cylinder head temperatures. The engine never ran hot on mogas, but I tend to think 100 degrees cooler is significant and probably better for the engine.
Anyone out there have a similar experience? My engine is a factory re manufactured engine with about 300 hours on it. I have no idea why straight mogas would run hotter that the blend.
I don't have any direct Mogas experience but I'm hoping that some of our members will respond. When I was up flying EAA's 172 I noticed that they had a Mogas truck and inquired about it. This was two years ago and they used Mogas on their 172. BTW, they make the 172 available for their employees to use. I have a contact there if you need it.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
I am a CFII, A&P, IA and have owned a '64 Cherokee 235 with a fixed pitch propeller. I bought my cherokee in 1999 after a crash and replaced a wing, engine mount and prop. In 2016 I moved to Sequim, Washington. They have Mogas available here. I bought the peterson STC and have run straight mogas for the last three years. I boroscope my cylinders and each 100 hr inspection. The cylinders, pistons and valves all look great. At Christmas we removed one cylinder because of low compressions and found a worn valve guide. It was fixed and reinstalled. Everything else looked great. I have installed a JPI 700, and monitor it religiously. On climb out I may have temps just above 400, but it cools to about 350 in cruise. I had an Apollo GX 50, but with Garmin talking about stopping database support for the unit, and because I have a lot of IFR days here in the winter, I installed a Garmin 175 and a Trutrak Vizion autopilot connected to it. An A&P can do the installation of both so there is no need to go to an avionics shop. The wiring is easy and if you search youtube you will find my video on the autopilot installation. The 235 is a great airplane, but the older models do not have as much legroom as the later models.
Hello Dr. Scott,
Thanks so much for writing about your plane and your mogas experience. Very useful info. When you get a chance, post a few pics of your plane, we all love to see what each other is flying.
Thanks again!
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Thanks Brooksby1 for your response. I am new to this aviation adventure so most everyone here knows more than me about almost everything, with one exception, and that is fuel. I do have 4 years of college chemistry and therefore understand technical information about oil and fuel. I even made biodiesel for 3 vehicles for 5 years, which of course is off topic but I mention it because I've studied fuel quite a bit. If mogas runs hotter, that is interesting but I am still wondering why and if it matters. There must be a reason for the "symptom" of increased temperatures. We have the same plane so do you see a cylinder head temperature difference between mogas and avgas? Eventually I will run a little experiment and run back to back avgas from one tank and mogas from another on the same day to eliminate other variables. BTW I have a JPI 930 so I have the enhanced capability as you do. I did buy this plane in part to be able to do cross countries and use mostly mogas. She's a thirsty beast but I can get no ethanol regular gas for about $2.25 so it is quite a savings even mixed 50/50.
Thanks for your thoughts!
PS I get the mogas delivered right out of the pipeline via bobtail so I am more sure of the quality.
Comments
Well, I do have a Corvette I could give you a ride in, but it only has one carburetor......
Lurch59
Too funny! I have a 1994 C3 white corvette in the hangar. It's coming home tomorrow after a cold winter.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Thanks for the follow up message above. I've sent a copy of your message to our A&P and I'm sure he'll appreciate it. Much thanks.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
I am having an engine monitor, the JPI EDI 900 installed in my Piper 235 next week. I have read a lot on LOP operation, and I've only seen 2 potential problems mentioned as you state. I also figure if the engine runs smooth and CHT are within normal limits, can't see any other problems. I will say I have a Peterson STC for mogas, and they clearly state no LOP operations on mogas. I wonder if it has not been tested and that's the reason for the caution. I will admit I'm the guy who constantly asks "why" in life, which can be annoying to some people. I don't mind being proven wrong. I just want to understand the logic behind the recommendation. I actually understand combustion pretty well and have had a few years of college chemistry so I understand the differences between avgas and mogas, tetraethyl lead, octane, etc.
Lurch59
Hi Scott,
Hey, that Corvette is fuel injected I think? Should we try LOP and see how she does?
My Corvette is a 69 and I took it out for a minute to warm it up a few days ago. There is still snow on the ground so it went back in the shop.
Lurch59
Old school A&P Thoughts: The limiting factor to leaning an engine is 400 degrees. This is the temperature when nasty things happen to pistons, rings, and cylinders. Detonation occures and all kinds of maintenance come up. If your engine is non-turbocharged, non fuel injected,it by design was constructed to not run at high altitudes. Running lean to peak at mid range altitudes then is for reducing fuel consumption, at the potential detriment of harm to overheated cylinders. Running an engine at 6-9 thousand feet and not leaning precisely will not get to the 400 degree temperature. Overheating an engine on climb out or decent is a real possiblity. A $500 cylinder head temperture guage (6 wire for a 6 cycliner engine) probably gives you the extra insurance you want, to not burn up an engine.
Good points, all. Thanks for your post.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Thank you for your thoughts. I've seen the graphs about how fast the strength of aluminum fall off at temps above 400 F, it's scary. I see Shanff is at 376 F, I will be interested to see my temps with new monitor installed. My CFI is not a fan of LOP in a carbureted engine.
Lurch59
Here is my opinion on CFI's. And no disrespect meant to any CFI. Most CFI's spend their time circling the pattern or doing stalls 15 miles from the home airport. Other than an occasional cross country for training purposes they don't get much practice on long cross countries, especially when they have to pay the bills. I would trust a long cross country flying pilot / owners opinion on things related to maintenance, efficiency, dollars long before I would a CFI. Of course, there are really good CFI's that actually have flying experience and yours may be one of them.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Comments on LOP operation for Lycoming normally aspirated engines:
Some Lycoming carbureted engines particularly the O-360 series can be run LOP. We do it all the time in our Cherokee 180 and we have had the engine borescoped at annuals to make sure it is not being damaged.
You will need to fully instrument the engine which means both EGT and CHT on all cylinders are being monitored in real time. Also, a fuel flow (FF) sensor should be part of the package as FF is a key factor to be monitored.
Part of your engine monitoring program is capturing the engine data and downloading it to a PC so that you can look at the data post flight. Not only are you looking for normal operation, the graphic representation may uncover a problem with your engine or with your methods of operation. I cannot stress how import it is to review the recorded engine data and in item 6 below a way is provided to view this on your PC for free.
In our engine (O-360) 10GPH or higher is typical for ROP operation. During LOP operation depending on altitude (higher more efficient) and RPM, the fuel burn will range between 7.5 to 8.5 GPH. During a long cross country this can translate into a considerable savings.
I am not going to tell you how to run LOP because the technique, although not too complicated, is something that needs adequate description and is covered in several articles available on the web. Once you understand the process you can do it without much trouble. Also note that you may need to add carburetor heat during the leaning process and in our case this makes the difference between a rough or smooth running engine. The following link has the best overall description of LOP operation and will answer many questions about it:
https://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning-198162-1.html
If this link doesn't work Google Savvy aviator #59 .
I am a fan of Mike Busch. His articles and books on how to operate and maintain GA piston engines are very good. I would recommend becoming a subscriber to his monthly newsletter (free). Also if you become a member, you can upload your engine monitoring data to his website and view it for free. When you start looking at your engine data, it will open your eyes as to what is really going on "under the hood." Also, he provides many articles on the theory and operation of LOP and what is going on inside your engine. His website is:
https://www.savvyaviation.com/
Note: The website provides different membership options that are fee based, but the basic level is free.
Thanks for the post. Most insightful.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Yes, thank to all. There is a lot of good information here. Scott, my CFI is an interesting guy. He has about 1800 hours and was a crop duster. My impression is not much scares him! He does seem to know quite a bit about planes and he hangs around the hangers working on planes and helping out the A and P mechanic. I think they are good friends. Methinks it is a good idea to keep my mouth shut and not voice any opinions yet. As we progress along I will ask some more about his opinions and how he came to his conclusions. He's a great CFI, I must say.
Lurch59
Great CFI's are hard to find. Hang on to him!
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
I recently got 2 quotes for my airplane insurance. They differ by about 30 percent which surprised me. Is it appropriate to ask questions about insurance on this forum?
Lurch59
Hi Lurch,
Yes it is. and we have our own aviation insurance expert, Sky Smith. Ask away and if need be I'll send your questions to him.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
That will be helpful, I'll look at both policies tomorrow. I suppose there is a page here that gives general advice for what kind of insurance I should be carrying. I don't know how common it is to own a plane while being trained. Also the plane is having stuff added to it and the value is increasing but how an I going to evaluate the additional insurance needs? There is no loan on the plane.
Today I went to visit my Piper 235 nicknamed the "Rice Rocket" A and P showed me a tangled web of old wires removed, cable for the RPM gauge, rusty and broken fuel senders, etc. He put in all new lines while the tanks were out. He got a good look at the spars? I thinks it's the spars, no corrosion. He thinks we have removed 30 lbs.! I am looking forward to seeing the JPI EDM 900 finished, The panel already looks very different and much less cluttered.
The A and P also thinks my original autopilot will work now. I'm not sure how sophisticated it is, but it's a start I guess.
Lurch59
One day at a time. Get your bird in the air and then continue restoring it. Let me know if you want to talk to Sky Smith. I'll get you his contact info.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Between the annual and the terrible weather here, I haven't been able to fly much, but yes, I am hoping to get the plane up a lot this spring and have my PPL by Summer. Today is a good day for me to talk to Sky Smith as I am at the office doing paperwork. thank you
Lurch59
Hi Lurch (do I call you that?),
His email is sky@skysmith.com. Tell him that I put you in touch with him...
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Thank you Scott, and my nickname is Lurch. My actual first name is Elden
Lurch59
Hmmmm, Lurch, eh. Like from the adams family?
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Yes, the nickname started because many years ago I worked with an electrical crew. I was the biggest guy on the jobsite, usually, so when there was a tough "wire pull" they would come get me and take me away from what I was doing. I used to grumble when they asked me and they thought it sounded like Lurch on the Adams Family. I guess he was 6'6" where I am 6'3", but close enough.
It could have been worse I suppose, they could have called me called Uncle Fester....
Lurch59
Uncle Fester, no hair, lol. Jackie Coogan, I think. Okay, Lurch!
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
I know what you mean, at 6' 5" when I was younger and thinner, I would do Ted Cassidy's throaty "You Rang?"
I've got a mogas question. I've been running mogas most of the last 100 hours. My mechanic showed me some damage to a Piper Cherokee 140 engine that was running mogas. The valves looked damaged from valve recession, a lot of signs of excessive heat, discolored heads etc. The engine needs an overhaul after 400 hours. He suggested I run 50/50 avgas and mogas.
Of course I have no idea if the other plane was running lean or there was some other issue. I did run the 50/50 mix last tanks and the engine monitor showed about 100 degrees less on the cylinder head temperatures. The engine never ran hot on mogas, but I tend to think 100 degrees cooler is significant and probably better for the engine.
Anyone out there have a similar experience? My engine is a factory re manufactured engine with about 300 hours on it. I have no idea why straight mogas would run hotter that the blend.
Lurch59
I don't have any direct Mogas experience but I'm hoping that some of our members will respond. When I was up flying EAA's 172 I noticed that they had a Mogas truck and inquired about it. This was two years ago and they used Mogas on their 172. BTW, they make the 172 available for their employees to use. I have a contact there if you need it.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
I am a CFII, A&P, IA and have owned a '64 Cherokee 235 with a fixed pitch propeller. I bought my cherokee in 1999 after a crash and replaced a wing, engine mount and prop. In 2016 I moved to Sequim, Washington. They have Mogas available here. I bought the peterson STC and have run straight mogas for the last three years. I boroscope my cylinders and each 100 hr inspection. The cylinders, pistons and valves all look great. At Christmas we removed one cylinder because of low compressions and found a worn valve guide. It was fixed and reinstalled. Everything else looked great. I have installed a JPI 700, and monitor it religiously. On climb out I may have temps just above 400, but it cools to about 350 in cruise. I had an Apollo GX 50, but with Garmin talking about stopping database support for the unit, and because I have a lot of IFR days here in the winter, I installed a Garmin 175 and a Trutrak Vizion autopilot connected to it. An A&P can do the installation of both so there is no need to go to an avionics shop. The wiring is easy and if you search youtube you will find my video on the autopilot installation. The 235 is a great airplane, but the older models do not have as much legroom as the later models.
Scott Brooksby, CFII, A&P, IA
Hello Dr. Scott,
Thanks so much for writing about your plane and your mogas experience. Very useful info. When you get a chance, post a few pics of your plane, we all love to see what each other is flying.
Thanks again!
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Thanks Brooksby1 for your response. I am new to this aviation adventure so most everyone here knows more than me about almost everything, with one exception, and that is fuel. I do have 4 years of college chemistry and therefore understand technical information about oil and fuel. I even made biodiesel for 3 vehicles for 5 years, which of course is off topic but I mention it because I've studied fuel quite a bit. If mogas runs hotter, that is interesting but I am still wondering why and if it matters. There must be a reason for the "symptom" of increased temperatures. We have the same plane so do you see a cylinder head temperature difference between mogas and avgas? Eventually I will run a little experiment and run back to back avgas from one tank and mogas from another on the same day to eliminate other variables. BTW I have a JPI 930 so I have the enhanced capability as you do. I did buy this plane in part to be able to do cross countries and use mostly mogas. She's a thirsty beast but I can get no ethanol regular gas for about $2.25 so it is quite a savings even mixed 50/50.
Thanks for your thoughts!
PS I get the mogas delivered right out of the pipeline via bobtail so I am more sure of the quality.
Lurch59