8GCBC wrote:

Fraser Farmer wrote:In my situation I'm paying half for premium Mogas what I would for 100LL at the airport, that adds up fast, like I could overhaul almost twice as often if needed. The fact is though the engine is looking and running great with great compression numbers and I never foul anything up with lead either, I actually get a lot of comments from the AME about the cleanliness of the engine and the great compression numbers. To be fair some of that can be attributed to my plane actually getting flown regularly as opposed to most of the GA aircraft he sees.
I am testing my gas for ethanol and I'm running out of my own bulk tank so if there are issues they should usually show up in my cars and trucks before my plane.

Definitely you have a success story. I certainly disdain cleaning spark plugs! God has blessed you Sir! Thank you for the level minded post.

I don't know about blessed but I am a Mogas fan for sure, and it has worked well for me.

I got to converse quite a bit with a fellow who had done a lot of the test piloting for a company that holds STCs for putting carbed 0-520s and 0-550s into Cessna 180s. They ran each of those configurations to the recommended overhaul interval on exclusively, Mogas without issue. He's also a big fan of Mogas. In the end they weren't able to get the STC for Mogas though, just for the carbed upsized engines in the 180. So a thing that I'm curious about is, what would be the issue with running Mogas through the stock injected i0-520 or i0-550, aside from the legality? Is it a greater risk of vapour lock?

About 255 hrs on these and never been cleaned. Fuel from the local Cenex station.

180Marty wrote:About 255 hrs on these and never been cleaned. Fuel from the local Cenex station.

Nice

Fraser Farmer wrote:

8GCBC wrote:

Fraser Farmer wrote:In my situation I'm paying half for premium Mogas what I would for 100LL at the airport, that adds up fast, like I could overhaul almost twice as often if needed. The fact is though the engine is looking and running great with great compression numbers and I never foul anything up with lead either, I actually get a lot of comments from the AME about the cleanliness of the engine and the great compression numbers. To be fair some of that can be attributed to my plane actually getting flown regularly as opposed to most of the GA aircraft he sees.
I am testing my gas for ethanol and I'm running out of my own bulk tank so if there are issues they should usually show up in my cars and trucks before my plane.

Definitely you have a success story. I certainly disdain cleaning spark plugs! God has blessed you Sir! Thank you for the level minded post.

I don't know about blessed but I am a Mogas fan for sure, and it has worked well for me.

I got to converse quite a bit with a fellow who had done a lot of the test piloting for a company that holds STCs for putting carbed 0-520s and 0-550s into Cessna 180s. They ran each of those configurations to the recommended overhaul interval on exclusively, Mogas without issue. He's also a big fan of Mogas. In the end they weren't able to get the STC for Mogas though, just for the carbed upsized engines in the 180. So a thing that I'm curious about is, what would be the issue with running Mogas through the stock injected i0-520 or i0-550, aside from the legality? Is it a greater risk of vapour lock?

Yes, vapor lock is the issue. Petterson has some great info on it. He ran quite a few tests but could not get away from that issue. I always ran mogas in my C180 as well, and my Citabria and 150 and 172. Wish I could do it in my 206 but not an option I'm willing to try with my family on board. For my fun plane that I'm going to build, it'll be mogas as well, but probably thriu a Yamaha motor...
Ted, interesting that the R44 Cadet POH calls out 91 as approved. The Raven II I work on strictly says 100LL. Must be because the Cadet is Derated?

Fraser Farmer wrote:

8GCBC wrote:

Fraser Farmer wrote:In my situation I'm paying half for premium Mogas what I would for 100LL at the airport, that adds up fast, like I could overhaul almost twice as often if needed. The fact is though the engine is looking and running great with great compression numbers and I never foul anything up with lead either, I actually get a lot of comments from the AME about the cleanliness of the engine and the great compression numbers. To be fair some of that can be attributed to my plane actually getting flown regularly as opposed to most of the GA aircraft he sees.
I am testing my gas for ethanol and I'm running out of my own bulk tank so if there are issues they should usually show up in my cars and trucks before my plane.

Definitely you have a success story. I certainly disdain cleaning spark plugs! God has blessed you Sir! Thank you for the level minded post.

I don't know about blessed but I am a Mogas fan for sure, and it has worked well for me.

I got to converse quite a bit with a fellow who had done a lot of the test piloting for a company that holds STCs for putting carbed 0-520s and 0-550s into Cessna 180s. They ran each of those configurations to the recommended overhaul interval on exclusively, Mogas without issue. He's also a big fan of Mogas. In the end they weren't able to get the STC for Mogas though, just for the carbed upsized engines in the 180. So a thing that I'm curious about is, what would be the issue with running Mogas through the stock injected i0-520 or i0-550, aside from the legality? Is it a greater risk of vapour lock?

Fuel injection engines are not getting the MoGas approvals as easy. I suspect vapor tension is the reason and detonation issues.

The fuel injected Lycoming I0-540-AE1A5 in the R44 II allows 100 unleaded. But, precludes MoGas 91.

R44 II POH Section 2 Limitations:

If you fly a lot and can get good consistent MoGas with the engine/airframe approvals, MoGas does have successful ops.

A1Skinner wrote:Ted, interesting that the R44 Cadet POH calls out 91 as approved. The Raven II I work on strictly says 100LL. Must be because the Cadet is Derated?

Very good question...

My readings:

R44 Cadet — O540-F1B5 Carbureted, 91 octane minimum

R44 Raven II — I0540-AE1A5 Fuel Injected, 100 octane minimum (new approvals)

Carb vs FI precludes lower octane in R44 II

R44 Raven II POH updated:

8GCBC wrote:

A1Skinner wrote:Ted, interesting that the R44 Cadet POH calls out 91 as approved. The Raven II I work on strictly says 100LL. Must be because the Cadet is Derated?

R44 Cadet — O540-F1B5 Carbureted, 91 octane minimum

R44 Raven II — 0540-AE1A5 Fuel Injected, 100 octane minimum (new approvals)

Carb vs FI precludes lower octane in R44 II

R44 Raven II POH updated:

I didnt realize the Cadet was Carb. Makes sense then. Thanks!

A1Skinner wrote:I didnt realize the Cadet was Carb. Makes sense then. Thanks!

You are welcome. Thank you for supporting alternative fuels!

The Cadet is an R44 Raven I without back seats. O540-F1B5.

I can confirm the vapor lock issue. One of the Callairs I leased had a finicky electric fuel pump. Occasionally the engine would quit in the field. Wiggle the switch and continue to march. First time I complained, the owner/mechanic said, "Hit it with a hammer." Second time I complained he said, "Don't whine." Third time he fixed it.

contactflying wrote:I can confirm the vapor lock issue. One of the Callairs I leased had a finicky electric fuel pump. Occasionally the engine would quit in the field. Wiggle the switch and continue to march. First time I complained, the owner/mechanic said, "Hit it with a hammer." Second time I complained he said, "Don't whine." Third time he fixed it.

So did that lock up on you in flight? Whenever I've heard of the issue coming up in Cessnas it is on a hot engine that's been turned off for a bit, go to fire it back up and the fuel is vapourized in the lines. I'm sure it's a total pain in the butt, even on the ground. When Patterson tried Mogas did the problem worsen beyond that? I can hardly imagine flowing fuel vapourizing in the lines during flight? Not that I want to try.

Always heard the story that sometime late - 70’s/early - 80’s there was a year when 100LL was extremely hard to get in AK due to some supply chain issue. The fuel injected guys would keep one tank with what little 100LL there was and another tank with car gas. Takeoff on the LL, switch and cruise on the car gas. Maybe BS but it sounds good.

gbflyer wrote:Always heard the story that sometime late - 70’s/early - 80’s there was a year when 100LL was extremely hard to get in AK due to some supply chain issue. The fuel injected guys would keep one tank with what little 100LL there was and another tank with car gas. Takeoff on the LL, switch and cruise on the car gas. Maybe BS but it sounds good.

When you think about it, they run fuel injected Cessnas all over the world and in some very remote and 3rd world locations, I'm sure there's been plenty of Mogas run through them.

gbflyer wrote:Always heard the story that sometime late - 70’s/early - 80’s there was a year when 100LL was extremely hard to get in AK due to some supply chain issue. The fuel injected guys would keep one tank with what little 100LL there was and another tank with car gas. Takeoff on the LL, switch and cruise on the car gas. Maybe BS but it sounds good.

Hopefully not getting ramp checked with a guy holding a fuel sampling cup. ha ha ha.

A big part of the reason I chose the engine in my Maule is that a Mogas STC was available. I've not taken advantage of it but if/when we lose access to 100LL I did not want a 180HP paperweight.

The Maule airframe requires modifications other than just a decal on the tank. A cooler port for the gascolator and a different fuel pump IIRC so its not an inexpensive process.

Mountain Doctor wrote:A big part of the reason I chose the engine in my Maule is that a Mogas STC was available. I've not taken advantage of it but if/when we lose access to 100LL I did not want a 180HP paperweight.

The Maule airframe requires modifications other than just a decal on the tank. A cooler port for the gascolator and a different fuel pump IIRC so its not an inexpensive process.

I did most of my flying in an area where there are security cameras and narcs everywhere both civil and government. My hangar neighbor was the FBI and the FSDO was not far either then plenty civilian Part 135/121 narcs snooping too. Much different than let’s say outback Alaska. I purchased a Peterson STC for the Scout just in case I was somewhere in which 100LL wasn’t available and to remain legal. I had my little ethanol tester, placards in place and an official POH supplement in the Scout. I was ready for the backcountry!

Well I arrived in Gustavus, Alaska which was out of 100LL. I needed more fuel to film the glaciers so GBFLYER bartered some MoGas! I could continue legally on my adventure deep in the mountains and film...

Good to have friends in the Alaska wilderness:

Just a bit of a correction. Petersen developed STCs for the IO470 and IO520 in the early 90s.The Cessna 188 C210 and Beech Baron are the STCd airframes. Vapor lock was never an issue. The high compression ratio was an issue and required the installation of a water/methanol anti-detonation injection system that kicks on when MP reaches 25” and/or CHTs reach 400F. A few years ago I talked to the outfit that took over the STC and further developed it. They said low pressure facet style pump were installed in the wings to make sure vapor lock didn’t occur in hot temps but they were rarely needed. Just watch for flickering of the fuel pressure to know if you needed to turn on the pumps. They had a C180 with a IO550 and were running it on mogas with their ADI system.

Maybe you guys were thinking of Petersen’s attempts at STCing fuel injected Lycomings which were not successful due to significant vapor lock issues with the Bendix system.

I’ve put 50hrs worth of mogas through my Continental IO360 without issue.

whee wrote:Just a bit of a correction. Petersen developed STCs for the IO470 and IO520 in the early 90s.The Cessna 188 C210 and Beech Baron are the STCd airframes. Vapor lock was never an issue. The high compression ratio was an issue and required the installation of a water/methanol anti-detonation injection system that kicks on when MP reaches 25” and/or CHTs reach 400F. A few years ago I talked to the outfit that took over the STC and further developed it. They said low pressure facet style pump were installed in the wings to make sure vapor lock didn’t occur in hot temps but they were rarely needed. Just watch for flickering of the fuel pressure to know if you needed to turn on the pumps. They had a C180 with a IO550 and were running it on mogas with their ADI system.

Maybe you guys were thinking of Petersen’s attempts at STCing fuel injected Lycomings which were not successful due to significant vapor lock issues with the Bendix system.

I’ve put 50hrs worth of mogas through my Continental IO360 without issue.

Very interesting. The compression ratio 9n a IO-520 is only 8.5:1. Same as a lot of the Lycomings that are approved for 91 octane Mogas. Wonder why the difference between motors. Just horsepower output? Why dont we need ADI on the high comp lycs?

Whee, Thank you for the STC refresher. I do remember now.

<break break>

Check out the ignition timing and compression ratio on TCDS IO-520 and IO-550:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/14b81c65a5fab42986257953004df52e/$FILE/E5ce%20rev%2026.pdf

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/557019137c0f8c6d86257953004c9c18/$FILE/E3SO%20rev%2011.pdf

8GCBC wrote:Whee, Thank you for the STC refresher. I do remember now.

<break break>

Check out the ignition timing and compression ratio on TCDS IO-520 and IO-550:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/14b81c65a5fab42986257953004df52e/$FILE/E5ce%20rev%2026.pdf

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/557019137c0f8c6d86257953004c9c18/$FILE/E3SO%20rev%2011.pdf

This is my point. The 520 has the same CR as the 160hp 0-320, but the timing is actually retarded further. So what other difference is there that allows the mogas for the 320 but not the 520 without ADI? Seems to me that if injection wasn't an issue the 520 should have no problem on mogas, as by the numbers it's more docile then the 320.

A1Skinner wrote:

8GCBC wrote:Whee, Thank you for the STC refresher. I do remember now.

<break break>

Check out the ignition timing and compression ratio on TCDS IO-520 and IO-550:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/14b81c65a5fab42986257953004df52e/$FILE/E5ce%20rev%2026.pdf

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/557019137c0f8c6d86257953004c9c18/$FILE/E3SO%20rev%2011.pdf

This is my point. The 520 has the same CR as the 160hp 0-320, but the timing is actually retarded further. So what other difference is there that allows the mogas for the 320 but not the 520 without ADI? Seems to me that if injection wasn't an issue the 520 should have no problem on mogas, as by the numbers it's more docile then the 320.

My personal thoughts “lean” towards the resulting fuel injection atomization gives a better mixture for a detonation scenario? Also, it might run a bit hotter? The engineering is definitely above my pay grade. Good questions for the STC holder. Good food for thought.

OK, I know some of the crew here probably want to know about Lycoming MSB388C Exhaust Valve & Guide Condition Check. And how unleaded vs leaded effects the valves sticking. Good sub topic eh?

Anybody have SB388C experience with (or without) alternative fuels? Better or worse?

https://www.lycoming.com/sites/default/files/Procedure%20to%20Determine%20Exhaust%20Value%20and%20Guide%20Condition.pdf

Note: Lycoming Webmaster spelled valve wrong in the URL.