I've had a '68 PA28-235C for about 12-years with the mogas STC. I was lucky the last 5-years that mogas was available at the home airport...prior to that I would get it where ever I could...the biggest issue with using 100LL was fouling spark plugs...they would foul buy the time I taxied to the runway. If your flying long cross countries and have to use 100LL, be sure to lean even on the ground taxiing.
After a hiatus due to Covid, I started taking a few lessons again and I soloed last Saturday! It went pretty smoothly. It's quite a thrill realizing it was up to me to get it back on the ground.
I also got my high performance endorsement. I'm not sure I would do my training in a Piper 235 with constant speed prop if I had to do it over again, but it is done now. Well, this stage of training anyway.
Congrats on your solo! As long as you live, that flight will be etched into your memory. The first thing I noticed was how fast the plane climbed with only one person, and how responsive it felt on the controls.
When you landed, did your instructor cut the tail off your shirt? Spray you with beer or champagne? Make you buy him/her a bottle of their favorite libation?
I had my shirt tail cut off by my instructor, and it's signed, dated, and includes the plane type, airport and tail number. That scrap of my shirt is framed and proudly displayed in my home.
You'll never forget your first solo. Congrats again!
My engine is in need of a rebuild! It has less than 500 hours and was a factory remanufactured, so obviously, this is a very unpleasant surprise. It was rebuilt in 2012.
The problems were discovered when a cylinder we were watching was losing compression. Upon removing the cylinder, rust was seen on the rod caps and the cam was pitted. The biggest surprise was damage to the cylinders and evidence of excessive heat such as a stretched valve stem and dimples on the exhaust system. The mechanic thinks it is due to mogas. He has taken apart another low-time engine recently with some of the same issues, minus the rust.
So, my question is, why was this plane STC'd for mogas if it damages the engine? There is evidence of pre-detonation and abnormal side loading on the bearings.
The other thing I have wondered about is how running around the pattern at full rich, 3200-4100 elevation affects the engine. How is the excessive fuel affecting the engine, when it was essentially the same full rich mixture for sea level? This can't be good, and does it cause combustion issues that might contribute to this issue?
I guess my big question is how some get away with running mogas and I did not? BTW, the plane spent a few years in Rhode Island before I purchased it. I am assuming the rust and heat issues are not related, but, what do I know.
Expensive lesson, but at least parts aren't stuck on a ship somewhere. I should be flying again in 3 months.
What is the plane and model of engine? Full rich operation at altitude leaves carbon everywhere but it is also very unlikely to cause heat or detonation type damage as this is an operating point well off the power curve and least likely to have things like pre-detonation.
Do you have any engine monitoring? What EGT temps do you typically see in climb and cruise?
Here is an article on MOGAS. If this was bought by an aviation retailer I don't see any issues. If gas from a gas station was used there could be a problem with the Ethanol used. For a fuel injection engine the risk is debris in an injector leaning out a cylinder.
I always take my oil caps off after every flight. There is an impressive cloud of steam that comes off. Water is the primary byproduct of combustion and some of it slips past the rings. As engines age and the bypass increases this gets progressively worse. By letting the steam out when the engine is hot you are releasing most of the water that would otherwise condense as the engine cools.
It is a Cherokee 235 with a 0-540 B4B5 engine. I have a JPI engine monitor and the temps are usually 380 on climb out and about 360 at cruise. I was having one cylinder at 408 once and once at 425 for a minute, but all the cylinders look the same.
No ethanol in the gas, I have it delivered via bobtail and check it myself for ethanol.
Lurch59, All those numbers seem fine and an O-540 is carb so no clogged injectors, etc. Those temps are normal too and even the brief time above 400 is in limits. How about exhaust temps?
Do you review the engine monitor data on a computer? Do you have the history prior to your ownership? Could there have been some extended downtime outside in RI prior to your ownership?
Sorry to hear you're having to go through a rebuild on a quarter time engine. Eric is spot on. It's not just the hours, but how long it took to accumulate those hours. 500 hrs in almost 10 yrs is not very much, but it's important to know how your engine arrived at that number. It could have been flown 250 hrs per year for 2 years, then may have sat for the next 7. Down time is what destroys engines. Rhode Island has a lot of coastal shoreline, and if the airplane was tied down/hangared anywhere near the coast, the salt water atmosphere could accelerate corrosion/rusting, especially if it was parked for a while.
When the rebuild and break-in are complete, consider the following tips;
1. Open up the oil dipstick tube for about 10 min after every flight. I've been doing this for years, and Eric mentioned it also. A lot of moisture escapes that would otherwise be trapped inside the crankcase where it will eventually condense and cause rust. Replace the dipstick so nothing can fall into the crankcase.
2. Keep the engine warm in the winter and transitional months. I leave my Tannis heater plugged in all winter with a blanket wrapped around the cowling. Ask on the Internet if you should do that, and you'll immediately find yourself involved in a war of words. From a scientific standpoint, in order for condensation to form, the temp of the engine needs to be at or near the dew point. The Tannis heater and the blanket keep the entire engine bay far above that point, so condensation cannot form. If rust or condensation is still a problem, consider an "engine dryer". It's a device that circulates crankcase air through desiccants to remove moisture. You can make your own or purchase them already built.
3. Use CamGuard at every oil change. I have no affiliation to the company or the product, but it works well on engines that don't run every day. My engine is a testimony.
When I began following the steps above, my engine oil analysis reports improved immediately, and my engine continues to run very well. By far the best thing you can do for your airplane is fly it often.
Thanks for the input. I have had it for almost 4 years. We have put almost 300 hours on it, or about 100 hours a year except 2020 when we suspended flying for a while because of Covid. Prior to that it had 200 hours or so over 6 years. I am not sure how the hours accumulated in Rhode Island.
I'm not hearing much about the mogas causing this. Of course, the question is how some are running mogas and not having any issues and my engine is gone. Could it be the rust caused the cylinder damage and abnormal bearing wear?
The mechanic here warned me about mogas use. He showed me an engine, I think out of a Cherokee 140, which needed an early rebuild and had similar issues, minus the rust.
I guess I am wanting to know the exact causation of the damage by running mogas vs avgas. For instance, a hydrocarbon is a hydrocarbon and it will burn and produce h2o and co2, right? I'm baiting the question, because I know it is not that simple. There are vapor pressures, isomers, octane values, etc. I was told that the mogas does not "flash" burn completely like avgas. I'm not sure that is true, but there is evidence of predetonation. Even the term predetonation is misused, the correct idea is spontaneous combustion in other parts of the cylinder. This happens because the sparkplug fires off the mixture near the plug, and raised the pressure in the cylinder and other areas ignite and flame fronts collide causing a knocking noise.
How does the STC get issued if mogas caused these problems?
Somebody smarter than me knows the answers, but I am pretty sure I could understand the answer if someone explains it to me!
It appears you already have a very good handle on the problem. You are correct, the formulation for AVgas differs significantly from Mogas.
There is a big misconception out there about high octane fuels and energy or power. Higher octane fuels do not contain more energy than lower octane fuels, nor will they make your engine produce more power. A higher octane fuel burns slower, resisting detonation. In the big picture, this allows an engine builder to utilize more compression (which does produce more power) or advance the timing more without detonation. However, our normally aspirated, spark-ignited aircraft engines run at a fixed compression ratio, and a fixed timing (at cruise).
There are advantages and disadvantages to both fuels. AVgas is a paraffin based fuel containing more Alkanes, and is a higher quality fuel that differs in vapor pressure, will store a lot longer than Mogas, and has better anti-knock properties. Paraffin based fuels also have a far higher boiling point, so at higher altitudes or temperatures, Mogas will vapor lock on you long before AVgas. That doesn't mean it will, but chemically speaking, AVgas has a big advantage. On the down side, AVgas's paraffin chemistry relies on tetra ethyl lead to achieve its octane rating, whereas Mogas contains more aromatic hydrocarbons to achieve the same rating.
Having Mogas sit in your tanks for more than 6 months is not recommended, and I've even heard no more than 3-6 weeks. Mogas will deteriorate, and if left long enough, will create a varnish when it dries. The upside is Mogas is significantly less expensive than AVgas, and since it does not contain lead, will not foul the spark plugs with lead deposits.
Automotive gasoline differs significantly from from Mogas, as most automotive fuels are formulated with 10% ethanol (E-10). Fuel containing ethanol should never be used in an aircraft. AVgas has never contained ethanol.
Lycoming (not Piper) has issued a service letter [Service Letter No. 185 B] regarding fuels and procedures including startup, taxiing, and shutdown. I've been told the shutdown procedure helps scavenge lead from the combustion chamber. Here's a link:
Here are a few important sections (cut and pasted):
The engine should be operated at engine speeds between 1000 and 1200 RPM after starting and during the initial warm-up period. Avoid prolonged closed throttle idle engine speed operation (when possible). At engine speeds from 1000 to 1200 RPM, the spark plug core temperatures are hot enough to activate the lead scavenging agents contained in the fuel which retards the formation of the lead salt deposits on the spark plugs and exhaust valve stems. Avoid rapid engine speed changes after start-up and use only the power settings required to taxi.
Rapid engine cool down from low power altitude changes, low power landing approach and/or engine shut-down too soon after landing or ground runs should be avoided.
Prior to the engine shut-down, the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilized. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds, then reduced to 1000-1200 RPM and shut-down immediately using the mixture control.
The service letter also states that automotive fuel should never be used in an aircraft engine. The service letter was published in 1988.
After completing my Masters, my professors begged me to stay and earn a PHD. I already had the thesis completed, but I didn't see a big advantage to the PHD for the direction I wanted to go. I don't regret it, but I sometimes wonder...
Lurch59 seems to have a good understanding of fuels as well as the problems they can cause, and posed an excellent question.
I just hope that when I respond like I did above, everyone's eyes don't glass over.
Thank you for your response. I'll mention that I have several years of college chemistry, so you are speaking my language. I will also mention that spent several years making biodiesel and ran it at 100 percent for several years in 3 different diesel vehicles. I still have all of them and they are performing well. I only mention this because Cummins recommends no more than 10 percent biodiesel, I ignored it without detriment. That makes me wonder if Lycoming has a reason from research why automotive fuel isn't recommended.
I suppose my complaint is that we rely on the FAA to verify STC's as being safe. Did the test exclude a longevity test? The evidence from the engine teardown does suggest pre-detonation and heat, but from what? I always ran excess required octane and often mixed it with avgas. I tested the fuel myself for methanol to be sure every batch was methanol-free.
Let's face it, 100LL is a convenient fuel that will work in all GA aircraft from HP turbos at 20k feet to my low compression, naturally aspirated 0-540 B4B5. My airplane doesn't need 100 octane, but something is wrong.
I bought the plane, partially because I didn't know what would happen with leaded fuel, and to use a cheaper fuel to save money. I can afford to go ahead and use avgas, but darn it, I feel misled.
I appreciate your references and tips, which I will use to keep my engine in better condition. I just wonder why others here have run mogas without issues. And of course, the battle of opinions between my mechanic, and the STC's for mogas.
As I poured my first batch of homemade biodiesel into my nearly new Excursion, my wife asked me if I was sure I knew what I was doing. I replied, "pretty sure". All of those vehicles operated at 0 AGL, so I was a little bolder to try an experimental fuel, lol!
I could tell just from your verbiage that you were knowledgeable in the subject, and figured we'd be on the same page.
Wish I could tell you what the root cause is for the damage sustained to your engine, but I'm left scratching my head so hard I've drawn blood. It almost sounds like it was over-leaned, or that there was a fuel delivery problem or air leaks in the intake system. Unfortunately, I'm at a loss, and now have to clean up the blood caused by scratching my noggin.
What MP, RPM, and fuel flow did you use during pattern work, cruise, etc.?
Have you had your temp probes checked for calibration?
I have not heard of any broad problems with MoGas aside from those burning pump gas with alcohol. Did you have any oil analysis work? Should have showed low lead at least.
I think 100LL alternatives will drive a revolution in engine health as much better synthetic oils would be available for longer life and lower drag.
Tough to overtemp on a carburetor unless the full power settings were consistently too lean overall and you would have seen that in CHT's. The reason is for fuel injection it is usually one partial injector running super lean and 3 (or 5 ) normal ones.
At 500 ft AGL we are at 22 manifold pressure and 2300 RPM. In the pattern we are 15 manifold pressure and 2300 RPM. The temp probes are all pretty new. I had he JPI 900 installed a couple of years ago and they were calibrated at that time.
I did have the oil analysis done once or twice, nothing unusual. I know it is better to track a trend, as I do analysis on all my diesel engines.
The engine was a factory reman, and has a new log book. I'm going to keep the cylinders and look at each one. I do wonder if the rust had anything to do with this, but, the rust probably occurred during low use and while the plane was in Rhode Island. But, would rusty cylinder walls go another 2-300 hours prior to failing? There is some rust on the rod caps.
Compressions were pretty good until last annual, where one was dropping off. We planned to check it again at oil change, but when the JPI engine tach failed, we checked it and found the original cylinder to be like 30 and another cylinder dropping off.
And yes, if I see evidence of excessive heat, why is it not showing up on EGT and CHT. I will download the information but I don't expect to see much because my flight instructor is an AP mechanic and he monitors that stuff pretty closely. My wife and I are both taking lessons together so he spends a lot of time watching things that we might miss as new pilots.
I'm going to talk to the other owner who had a Cherokee 140 and had to rebuild a low time engine, and was running mogas.
I will mention that one exhaust valve stem was stretched .004 under spec. I'll get some pics and post them. It will take a couple of weeks as I am real busy now, but I have 2 or 3 months before I am airborne again. And, you know when they tell you 2-3 months, that really means 3!
Comments
I've had a '68 PA28-235C for about 12-years with the mogas STC. I was lucky the last 5-years that mogas was available at the home airport...prior to that I would get it where ever I could...the biggest issue with using 100LL was fouling spark plugs...they would foul buy the time I taxied to the runway. If your flying long cross countries and have to use 100LL, be sure to lean even on the ground taxiing.
Thanks for your comments
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.
Need help? Let me know!
After a hiatus due to Covid, I started taking a few lessons again and I soloed last Saturday! It went pretty smoothly. It's quite a thrill realizing it was up to me to get it back on the ground.
I also got my high performance endorsement. I'm not sure I would do my training in a Piper 235 with constant speed prop if I had to do it over again, but it is done now. Well, this stage of training anyway.
Lurch59
Lurch59;
Congrats on your solo! As long as you live, that flight will be etched into your memory. The first thing I noticed was how fast the plane climbed with only one person, and how responsive it felt on the controls.
When you landed, did your instructor cut the tail off your shirt? Spray you with beer or champagne? Make you buy him/her a bottle of their favorite libation?
I had my shirt tail cut off by my instructor, and it's signed, dated, and includes the plane type, airport and tail number. That scrap of my shirt is framed and proudly displayed in my home.
You'll never forget your first solo. Congrats again!
Jim "Doc Griff" Griffin
PA28 - 161
Chicago area
Roger that! Congrats on surviving, lol. Now it's on to the next goal. A Cessna Citation?
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.
Need help? Let me know!
If I'm going for a Cessna Citation, first I will need a VERY successful Go Fund me page.
Lurch59
We can share one, lol. I've been lusting over one for a really long time!
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.
Need help? Let me know!
My engine is in need of a rebuild! It has less than 500 hours and was a factory remanufactured, so obviously, this is a very unpleasant surprise. It was rebuilt in 2012.
The problems were discovered when a cylinder we were watching was losing compression. Upon removing the cylinder, rust was seen on the rod caps and the cam was pitted. The biggest surprise was damage to the cylinders and evidence of excessive heat such as a stretched valve stem and dimples on the exhaust system. The mechanic thinks it is due to mogas. He has taken apart another low-time engine recently with some of the same issues, minus the rust.
So, my question is, why was this plane STC'd for mogas if it damages the engine? There is evidence of pre-detonation and abnormal side loading on the bearings.
The other thing I have wondered about is how running around the pattern at full rich, 3200-4100 elevation affects the engine. How is the excessive fuel affecting the engine, when it was essentially the same full rich mixture for sea level? This can't be good, and does it cause combustion issues that might contribute to this issue?
I guess my big question is how some get away with running mogas and I did not? BTW, the plane spent a few years in Rhode Island before I purchased it. I am assuming the rust and heat issues are not related, but, what do I know.
Expensive lesson, but at least parts aren't stuck on a ship somewhere. I should be flying again in 3 months.
Lurch
Lurch59
What is the plane and model of engine? Full rich operation at altitude leaves carbon everywhere but it is also very unlikely to cause heat or detonation type damage as this is an operating point well off the power curve and least likely to have things like pre-detonation.
Do you have any engine monitoring? What EGT temps do you typically see in climb and cruise?
Here is an article on MOGAS. If this was bought by an aviation retailer I don't see any issues. If gas from a gas station was used there could be a problem with the Ethanol used. For a fuel injection engine the risk is debris in an injector leaning out a cylinder.
https://generalaviationnews.com/2011/03/16/10-mogas-myths/
I always take my oil caps off after every flight. There is an impressive cloud of steam that comes off. Water is the primary byproduct of combustion and some of it slips past the rings. As engines age and the bypass increases this gets progressively worse. By letting the steam out when the engine is hot you are releasing most of the water that would otherwise condense as the engine cools.
Sorry to hear about your engine.
Eric
Eric Panning
1981 Seneca III
Hillsboro, OR (KHIO)
It is a Cherokee 235 with a 0-540 B4B5 engine. I have a JPI engine monitor and the temps are usually 380 on climb out and about 360 at cruise. I was having one cylinder at 408 once and once at 425 for a minute, but all the cylinders look the same.
No ethanol in the gas, I have it delivered via bobtail and check it myself for ethanol.
Lurch59
Lurch59, All those numbers seem fine and an O-540 is carb so no clogged injectors, etc. Those temps are normal too and even the brief time above 400 is in limits. How about exhaust temps?
Do you review the engine monitor data on a computer? Do you have the history prior to your ownership? Could there have been some extended downtime outside in RI prior to your ownership?
Eric Panning
1981 Seneca III
Hillsboro, OR (KHIO)
Lurch;
Sorry to hear you're having to go through a rebuild on a quarter time engine. Eric is spot on. It's not just the hours, but how long it took to accumulate those hours. 500 hrs in almost 10 yrs is not very much, but it's important to know how your engine arrived at that number. It could have been flown 250 hrs per year for 2 years, then may have sat for the next 7. Down time is what destroys engines. Rhode Island has a lot of coastal shoreline, and if the airplane was tied down/hangared anywhere near the coast, the salt water atmosphere could accelerate corrosion/rusting, especially if it was parked for a while.
When the rebuild and break-in are complete, consider the following tips;
1. Open up the oil dipstick tube for about 10 min after every flight. I've been doing this for years, and Eric mentioned it also. A lot of moisture escapes that would otherwise be trapped inside the crankcase where it will eventually condense and cause rust. Replace the dipstick so nothing can fall into the crankcase.
2. Keep the engine warm in the winter and transitional months. I leave my Tannis heater plugged in all winter with a blanket wrapped around the cowling. Ask on the Internet if you should do that, and you'll immediately find yourself involved in a war of words. From a scientific standpoint, in order for condensation to form, the temp of the engine needs to be at or near the dew point. The Tannis heater and the blanket keep the entire engine bay far above that point, so condensation cannot form. If rust or condensation is still a problem, consider an "engine dryer". It's a device that circulates crankcase air through desiccants to remove moisture. You can make your own or purchase them already built.
3. Use CamGuard at every oil change. I have no affiliation to the company or the product, but it works well on engines that don't run every day. My engine is a testimony.
When I began following the steps above, my engine oil analysis reports improved immediately, and my engine continues to run very well. By far the best thing you can do for your airplane is fly it often.
Keep us posted on your progress.
Jim "Doc Griff" Griffin
PA28 - 161
Chicago area
Thanks for the input. I have had it for almost 4 years. We have put almost 300 hours on it, or about 100 hours a year except 2020 when we suspended flying for a while because of Covid. Prior to that it had 200 hours or so over 6 years. I am not sure how the hours accumulated in Rhode Island.
I'm not hearing much about the mogas causing this. Of course, the question is how some are running mogas and not having any issues and my engine is gone. Could it be the rust caused the cylinder damage and abnormal bearing wear?
The mechanic here warned me about mogas use. He showed me an engine, I think out of a Cherokee 140, which needed an early rebuild and had similar issues, minus the rust.
I guess I am wanting to know the exact causation of the damage by running mogas vs avgas. For instance, a hydrocarbon is a hydrocarbon and it will burn and produce h2o and co2, right? I'm baiting the question, because I know it is not that simple. There are vapor pressures, isomers, octane values, etc. I was told that the mogas does not "flash" burn completely like avgas. I'm not sure that is true, but there is evidence of predetonation. Even the term predetonation is misused, the correct idea is spontaneous combustion in other parts of the cylinder. This happens because the sparkplug fires off the mixture near the plug, and raised the pressure in the cylinder and other areas ignite and flame fronts collide causing a knocking noise.
How does the STC get issued if mogas caused these problems?
Somebody smarter than me knows the answers, but I am pretty sure I could understand the answer if someone explains it to me!
Lurch59
Lurch;
It appears you already have a very good handle on the problem. You are correct, the formulation for AVgas differs significantly from Mogas.
There is a big misconception out there about high octane fuels and energy or power. Higher octane fuels do not contain more energy than lower octane fuels, nor will they make your engine produce more power. A higher octane fuel burns slower, resisting detonation. In the big picture, this allows an engine builder to utilize more compression (which does produce more power) or advance the timing more without detonation. However, our normally aspirated, spark-ignited aircraft engines run at a fixed compression ratio, and a fixed timing (at cruise).
There are advantages and disadvantages to both fuels. AVgas is a paraffin based fuel containing more Alkanes, and is a higher quality fuel that differs in vapor pressure, will store a lot longer than Mogas, and has better anti-knock properties. Paraffin based fuels also have a far higher boiling point, so at higher altitudes or temperatures, Mogas will vapor lock on you long before AVgas. That doesn't mean it will, but chemically speaking, AVgas has a big advantage. On the down side, AVgas's paraffin chemistry relies on tetra ethyl lead to achieve its octane rating, whereas Mogas contains more aromatic hydrocarbons to achieve the same rating.
Having Mogas sit in your tanks for more than 6 months is not recommended, and I've even heard no more than 3-6 weeks. Mogas will deteriorate, and if left long enough, will create a varnish when it dries. The upside is Mogas is significantly less expensive than AVgas, and since it does not contain lead, will not foul the spark plugs with lead deposits.
Automotive gasoline differs significantly from from Mogas, as most automotive fuels are formulated with 10% ethanol (E-10). Fuel containing ethanol should never be used in an aircraft. AVgas has never contained ethanol.
Lycoming (not Piper) has issued a service letter [Service Letter No. 185 B] regarding fuels and procedures including startup, taxiing, and shutdown. I've been told the shutdown procedure helps scavenge lead from the combustion chamber. Here's a link:
https://www.lycoming.com/sites/default/files/SL185B Fuel, Higher Octane Aviation, Use of 100LL for Engines Rated 80_87 Octane (1).pdf
Here are a few important sections (cut and pasted):
The engine should be operated at engine speeds between 1000 and 1200 RPM after starting and during the initial warm-up period. Avoid prolonged closed throttle idle engine speed operation (when possible). At engine speeds from 1000 to 1200 RPM, the spark plug core temperatures are hot enough to activate the lead scavenging agents contained in the fuel which retards the formation of the lead salt deposits on the spark plugs and exhaust valve stems. Avoid rapid engine speed changes after start-up and use only the power settings required to taxi.
Rapid engine cool down from low power altitude changes, low power landing approach and/or engine shut-down too soon after landing or ground runs should be avoided.
Prior to the engine shut-down, the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilized. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds, then reduced to 1000-1200 RPM and shut-down immediately using the mixture control.
The service letter also states that automotive fuel should never be used in an aircraft engine. The service letter was published in 1988.
Jim "Doc Griff" Griffin
PA28 - 161
Chicago area
Thanks Griff. So when are you getting your PHD?
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.
Need help? Let me know!
Scott: Thanks, that's quite a compliment!
After completing my Masters, my professors begged me to stay and earn a PHD. I already had the thesis completed, but I didn't see a big advantage to the PHD for the direction I wanted to go. I don't regret it, but I sometimes wonder...
Lurch59 seems to have a good understanding of fuels as well as the problems they can cause, and posed an excellent question.
I just hope that when I respond like I did above, everyone's eyes don't glass over.
Jim "Doc Griff" Griffin
PA28 - 161
Chicago area
I think you need to change your signature from 'Jim "Griff" Griffin' to just "Doc Griffin". We'll call you Doc from now on.
Scott Sherer
Wright Brothers Master Pilot, FAA Commercial Pilot
Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.
Need help? Let me know!
LOL!
Jim "Doc Griff" Griffin
PA28 - 161
Chicago area
Hi Griff,
Thank you for your response. I'll mention that I have several years of college chemistry, so you are speaking my language. I will also mention that spent several years making biodiesel and ran it at 100 percent for several years in 3 different diesel vehicles. I still have all of them and they are performing well. I only mention this because Cummins recommends no more than 10 percent biodiesel, I ignored it without detriment. That makes me wonder if Lycoming has a reason from research why automotive fuel isn't recommended.
I suppose my complaint is that we rely on the FAA to verify STC's as being safe. Did the test exclude a longevity test? The evidence from the engine teardown does suggest pre-detonation and heat, but from what? I always ran excess required octane and often mixed it with avgas. I tested the fuel myself for methanol to be sure every batch was methanol-free.
Let's face it, 100LL is a convenient fuel that will work in all GA aircraft from HP turbos at 20k feet to my low compression, naturally aspirated 0-540 B4B5. My airplane doesn't need 100 octane, but something is wrong.
I bought the plane, partially because I didn't know what would happen with leaded fuel, and to use a cheaper fuel to save money. I can afford to go ahead and use avgas, but darn it, I feel misled.
I appreciate your references and tips, which I will use to keep my engine in better condition. I just wonder why others here have run mogas without issues. And of course, the battle of opinions between my mechanic, and the STC's for mogas.
As I poured my first batch of homemade biodiesel into my nearly new Excursion, my wife asked me if I was sure I knew what I was doing. I replied, "pretty sure". All of those vehicles operated at 0 AGL, so I was a little bolder to try an experimental fuel, lol!
Thanks,
Lurch
Lurch59
I could tell just from your verbiage that you were knowledgeable in the subject, and figured we'd be on the same page.
Wish I could tell you what the root cause is for the damage sustained to your engine, but I'm left scratching my head so hard I've drawn blood. It almost sounds like it was over-leaned, or that there was a fuel delivery problem or air leaks in the intake system. Unfortunately, I'm at a loss, and now have to clean up the blood caused by scratching my noggin.
What MP, RPM, and fuel flow did you use during pattern work, cruise, etc.?
Have you had your temp probes checked for calibration?
Jim "Doc Griff" Griffin
PA28 - 161
Chicago area
I have not heard of any broad problems with MoGas aside from those burning pump gas with alcohol. Did you have any oil analysis work? Should have showed low lead at least.
I think 100LL alternatives will drive a revolution in engine health as much better synthetic oils would be available for longer life and lower drag.
Tough to overtemp on a carburetor unless the full power settings were consistently too lean overall and you would have seen that in CHT's. The reason is for fuel injection it is usually one partial injector running super lean and 3 (or 5 ) normal ones.
Could it have been an issue with the overhaul?
Eric Panning
1981 Seneca III
Hillsboro, OR (KHIO)
At 500 ft AGL we are at 22 manifold pressure and 2300 RPM. In the pattern we are 15 manifold pressure and 2300 RPM. The temp probes are all pretty new. I had he JPI 900 installed a couple of years ago and they were calibrated at that time.
I did have the oil analysis done once or twice, nothing unusual. I know it is better to track a trend, as I do analysis on all my diesel engines.
The engine was a factory reman, and has a new log book. I'm going to keep the cylinders and look at each one. I do wonder if the rust had anything to do with this, but, the rust probably occurred during low use and while the plane was in Rhode Island. But, would rusty cylinder walls go another 2-300 hours prior to failing? There is some rust on the rod caps.
Compressions were pretty good until last annual, where one was dropping off. We planned to check it again at oil change, but when the JPI engine tach failed, we checked it and found the original cylinder to be like 30 and another cylinder dropping off.
And yes, if I see evidence of excessive heat, why is it not showing up on EGT and CHT. I will download the information but I don't expect to see much because my flight instructor is an AP mechanic and he monitors that stuff pretty closely. My wife and I are both taking lessons together so he spends a lot of time watching things that we might miss as new pilots.
I'm going to talk to the other owner who had a Cherokee 140 and had to rebuild a low time engine, and was running mogas.
Thank you for your input!
Lurch59
Lurch59, let us know what you find out. If you are not seeing excess heat in EGT or CHT then it seems unlikely to be detonation or even pre-ignition.
Here is what detonation looks like
https://blog.aopa.org/aopa/2015/04/13/destroy-your-engine/
Eric Panning
1981 Seneca III
Hillsboro, OR (KHIO)
I will mention that one exhaust valve stem was stretched .004 under spec. I'll get some pics and post them. It will take a couple of weeks as I am real busy now, but I have 2 or 3 months before I am airborne again. And, you know when they tell you 2-3 months, that really means 3!
Lurch59