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Thread: proper leaning, premiun auto gas in an emergency

  1. #1
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    Default proper leaning, premiun auto gas in an emergency

    I had an interesting flight today. A 260 mile trip into a 15 mph headwind (I saw some 78 mph ground speeds).
    I leaned the old SWAG way; pulled the mixture out till the engine almost died, then pushed the mixture in till it smoothed out. I got to thinking about running too lean while I was just setting there trying to hold a heading and altitude (its was about 5:30 and bumpy). That's my first question: can I run too lean when I'm only generating 80 hp and do i need to worry about detonation?
    Now for question 2: 24 Miles fron my destination airport I chickened out and diverted to another airport to buy gas. When I got on the ground the airport was closed (Garmin database was wrong again), I called the emergency number and ended up waiting almost two hours for the attendant to show up and sell me some 100 low lead. The first guy I called was long gone and far away but he offered to call one of his buddies and have him come over and sell me a little premium car gas to get me to my destination. I declined, but kept thinking about it till I finally got fueled up. That's question 2: Would a few gallons of premuim car gas have worked or would it hurt the engine? One final note: It only took 17 gal to fill her up. I could have made it to my destination easily. But I don't feel bed about that. Live coward, dead hero and all that stuff!

  2. #2
    Senior Member randylervold's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    First question: if you're running at low horsepower (really anything below 75%, but especially below 65%) then no, you can't possibly run too lean and hurt anything. I do it all the time... pull the power way down, lean the bajezzus out of it, and watch with great joy as the fuel flow shows 4.5 gph or some such frugal figure. Of course this is keeping your engine cooler and cleaner inside as well. Be sure and richen it up though when it's time to climb.

    Second question: We will not approve the CC340 for auto fuel because virtually all auto fuel now has ethanol it which creates all sorts of problems, plus fuel quality can vary from country to country and you never know for sure what you're getting. That said the engine should run just fine in a pinch on PREMIUM auto fuel without detonation.

    Lastly, good job Rick on the fuel management judgment call -- better safe than in a mountain canyon dead somewhere because you "thought you could make it". With time you'll judgment will improve in forecasting range.
    Randy Lervold

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    Senior Member Dan L's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    I've used Premium ethanol-free car gas a few times in a pinch. No noticeable change in egt or cht temps. And it is always diluted to some extent with remaining 100LL.

    Not sure why that got underlined. I probably touched something on the iPad.
    Flying Carbon Cub EX #11 since 2011

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    Default Re: proper leaning, premiun auto gas in an emergency

    Is anyone out there running there cc340 LOP using the Dynon d180 for information? I have been doing this a little at 55% power or less and its interesting not only do you burn lots less gas but the 3,4 cyl. Temps go down by 60 degrees and the front,1,2 cylinders go up by 50 degrees!! Haven't really figured that one out . Any ideas? Royce

  5. #5
    Senior Member randylervold's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    Yes, I've been flying LOP at low power settings ever since setting foot inside CC over 4 years ago, wouldn't cruise any other way. ;-)
    Randy Lervold

  6. #6
    Senior Member chipallen's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    Ditto here, Randy. LOP in my Baron is bit more "scientific", but in the CC, it's the only way to fly at low power settings.
    Chip Allen
    SWT Aviation, Inc.
    Cubcrafters Southeast Sales Center
    Marietta, GA
    www.swtaviation.com

  7. #7
    Senior Member Steve Y's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    Has Lycoming come out with New leaning recommendations from what I have been taught for years?

    "Lycoming is in complete agreement that it is possible to operate an engine on the lean side of peak TIT. It is done on engines in our well-instrumented Experimental Test laboratory every day. There is nothing detrimental in operating an engine in this manner. However, we can attest to the fact that things that work well in the test laboratory have not always proven successful in service. In the sales literature provided for this “new” technique, it is stated that Lycoming recommended this operational procedure in an owner’s manual that dates back to the late ‘60’s. No mention is made why it is no longer recommended on our present engines. The fact is that the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues. Burned pistons, valves, ruined rod and main bearings were traced to the inability of pilots to utilize this technique with the instrumentation and distractions found in the typical general aviation aircraft. If Lycoming felt that this was indeed an efficient and reliable method of operation, you can be sure that it would be in our recommended procedures."

    Very interesting topic!
    Steve

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    Default Re: proper leaning, premiun auto gas in an emergency

    If I am 60 degrees cooler LOP than I am ROP then how will I burn up cylinders and rods and such doing this at lower(55%) power settings? Some say fuel is a coolant but rich of peak temps are higher. To rich in the 340 and it runs to rough to see if fuel is a coolant or not. Interesting thread. Any one out there with high time running LOP??
    I agree with Chip as LOP in my IO540 fuel injected RV 10 was a entirely different animal. Thoughts? RR

  9. #9
    Senior Member randylervold's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    Quote Originally Posted by Steve Y View Post
    Has Lycoming come out with New leaning recommendations from what I have been taught for years?

    "Lycoming is in complete agreement that it is possible to operate an engine on the lean side of peak TIT. It is done on engines in our well-instrumented Experimental Test laboratory every day. There is nothing detrimental in operating an engine in this manner. However, we can attest to the fact that things that work well in the test laboratory have not always proven successful in service. In the sales literature provided for this “new” technique, it is stated that Lycoming recommended this operational procedure in an owner’s manual that dates back to the late ‘60’s. No mention is made why it is no longer recommended on our present engines. The fact is that the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues. Burned pistons, valves, ruined rod and main bearings were traced to the inability of pilots to utilize this technique with the instrumentation and distractions found in the typical general aviation aircraft. If Lycoming felt that this was indeed an efficient and reliable method of operation, you can be sure that it would be in our recommended procedures."

    Very interesting topic!
    Steve
    Steve, it appears the above reference is for turbocharged engines with the reference to TIT (turbine inlet temp). I think the single biggest factor in running our planes LOP is to do so at a low power setting. Test after test has show that you can't hurt anything when done at low power so bad engine management technique, as referenced above, doesn't harm anything. There is lots of material written on this, just google "lean of peak" and Mike Busch, George Braly, or Kas Thomas who have all written extensively on it.
    Randy Lervold

  10. #10
    Senior Member turbopilot's Avatar
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    Default Re: proper leaning, premiun auto gas in an emergency

    I looked into this subject in 2010 here.

    Bottom line is that because of limitations of the carburetor and induction system, in my airplane you can only run half the engine LOP without it getting pretty rough.
    Bob Anderson, CC11-00316, N382RA

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