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Carburetor Icing 0-540?

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  • Carburetor Icing 0-540?

    I am new to the O-540. Flown mostly continentals all my life. Is the O-540 prone to carb icing? Has anyone in this group ever gotten carb icing in an 0-540? Thanks

  • #2
    Hello Bernie. In my time flying an O540 I got carb ice once. Noticed it and got rid of it fast. My understanding is that Continentals ice up much more often than Lycs. Mark


    • #3
      I would have assumed this had everything to do with the throttle body you install, you have a range of choices. The throttle assembly is sized to suit the engine - but overall the engine doesn't dictate a fixed carb (with fixed icing characteristics).

      If you are worried, go for fuel injection. It's fantastic for increased power, economy / efficiency, and very popular in the Bearhawk community.
      Last edited by Battson; 08-04-2022, 09:59 PM.


      • #4
        Hey Bernie

        I have a O-540-J in my Maule and it is terrible for carb icing at anything less than full throttle. I don't know if it is systemic with this engine in Maules or if I am just "lucky" :-) Regardless, I decided to modify the O-540-A that I bought and overhauled for the Bearhawk to have a Bendix fuel injection system (that I bought used off of the Vans Forums). I had the same injection unit on the IO-360-A3B6D in my RV-8 for years and loved it.

        YMMV, Batteries not included, Objects in mirror are closer than they appear, etc.


        Maule M5-235C C-GJFK
        Bearhawk 4A #1078 (Scratch building - C-GPFG reserved)
        RV-8 C-GURV (Sold)


        • rodsmith
          rodsmith commented
          Editing a comment
          That's really interesting. I flew a Maule with the same engine in Alaska for over 500 hours. Believe the only time I ever pulled carb heat on was to check it before takeoff. Wonder why such different experiences?

        • rv8bldr
          rv8bldr commented
          Editing a comment
          Hey Rod.

          I have no idea. It makes no sense. Maybe the air is moister here in flying season (Eastern Ontario?) However, it has happened enough times that I know it isn't my imagination. If I am just tooling around at 20/20 turning dinosaurs into engine noise, I periodically put carb heat on as a preventative measure now. If I am going somewhere, I am in the "oversquare" club with WOT and about 2000 RPM. At 6500' that yields about 125 kts TAS and 11.2 GPH. I have the three blade McCauley prop.

      • #5
        I have a quote from Bob for a carbureted engine (O-540). The quote indicates a carb temperature probe.

        But I'm with Battson... Fuel injection is the way to go. Hot starting is my only complaint there.
        Rob Caldwell
        Lake Norman Airpark (14A), North Carolina
        EAA Chapter 309
        Model B Quick Build Kit Serial # 11B-24B / 25B
        YouTube Channel:
        1st Flight May 18, 2021


        • #6
          I've never seen carb ice in a lycoming. I have a carb temp sensor and only in the winter does it reach a temp that ice could even form. When it's too cold to have any water in the air. This is because the carb is heated by the oil pan it's bolted to. There might be a lycoming configuration that's not true, but I don't know of one.

          Continentals on the other hand require you to carry tequila and a blender for all the ice the make.

          Injection is nice, but if you already own the carb, you won't make the fuel savings back over injection before the 2000 hour overhaul so just run it.


          • #7
            Thanks for all the input. Appreciate it


            • #8
              Originally posted by zkelley2 View Post

              Injection is nice, but if you already own the carb, you won't make the fuel savings back over injection before the 2000 hour overhaul so just run it.
              Err em, are you kidding?

              Most people with injection are saving up to $75 (NZD) per hour with these fuel prices these days, by running LOP due to having fuel injection. Something that almost all carb engines will not do. To continue the example given, over 2,000 hrs flying that is more than enough to pay for a brand new engine (with injection fitted).
              Last edited by Battson; Yesterday, 04:03 PM.


              • zkelley2
                zkelley2 commented
                Editing a comment
                Injection takes the mogas possibilities away. Raising the fuel cost about $2us a gallon here. Also, my hourly total fuel cost is only about $90NZD. I can't possibly save $75/hr.

              • Battson
                Battson commented
                Editing a comment
                We can discuss the details, but it easily pays for itself either way.
                They can't keep fuel prices artificially low forever, so it's only getting cheaper
                I was told by my engine manufacturer that I could still run mogas with injection, but over here there's really no need.

              • zkelley2
                zkelley2 commented
                Editing a comment
                I was going to swap the carb for injection when I was building. I ended up not doing that because it would cost more in fuel over the life of the engine.

                You can't get the mogas STC on any injected lycoming. The issue is the mechanical fuel pump gets quite warm are you can in theory have boiling fuel at the inlet. The inline boost pump should take care of that, but it's not ideal IMO. Not that we need an STC, but I'd not personally run mogas through a mechnical pump. EFII, sure. Honestly for the price of getting bendix injection, I'd go full EFI instead.

                100LL is $7.63 here right now.
                Premium ethanol free mogas is $4.99

                I burn 11gph in cruise, let's assume the typical injection and LOP ops reduces fuel burn by 1gph.

                $54.89/hr for mogas. $76.30/hr for low lead burning 1gph less. After 2000 hours the fuel injection will have cost me $42,820 more. Or more than the overhaul.

                Low lead will never be cheaper than mogas, even the new gami stuff is supposed to be about the same price.

                And I also have a need to run mogas that isn't just cost. 2-3 times a year I end up in a village in need of fuel and they don't sell anything but 87(r+m/2) at the car pump you have to taxi through town to get. That's been a lifesaver. Which is also why I have the SDS CPI, so I can run a timing map that 87 is safe on when necessary.