Running Methanol RC Engines On Gasoline

Methanol is a popular fuel for small engines used in radio-controlled models, but comes at a higher price than gasoline. It’s also harder to source and can be a mite corrosive, too. Gasoline comes with some benefits, but running it in a methanol engine usually requires some mods. [David] and [Bert] worked together to build a mixture controller for just this purpose.

The controller uses a solenoid to control the flow of gasoline to a conventional methanol-tuned carburetor for a small RC engine, allowing it to be accurately tuned to run gasoline well across the whole RPM range. Having gone through many revisions, all documented in a big forum thread, the latest version uses a Seeduino Xiao controller and a BMP280 pressure and temperature sensor for determining the right fuel/air mixture for the conditions. A small OLED screen can optionally be fitted to help with configuration of the mixture controller.

The system has worked well in testing, with [David] and [Bert] reporting that they have “converted engines as small as 0.3 CID up to large radials with this system.” It’s a promising tool that could be handy to have in the RC modeller’s arsenal.

These tiny engines have other applications too; they can make for one crazy power drill, that’s for sure!

33 thoughts on “Running Methanol RC Engines On Gasoline

  1. Methanol is nasty to handle as well. The mean LD50 for humans is 56.2 g and 3 grams ingested will cause blindness.

    The problem is that methanol is converted into formaldehyde, formate, and formic acid in the liver. These cause things like the destruction of the optic nerve, and bleeding in the brain. Spilling it on your hands, breathing the fumes, etc. cause significant exposure and damage, and the remedy is to “dilute” the products of methanol metabolism by slowing down the metabolism – essentially by drinking ethanol.

      1. I got some in my mouth long ago… My engine was flooded, and backfired when I attempted to start it and spat liquid fuel out of the crankcase into my face. It was unpleasant to say the least. I’ve since switched to small gasoline engines in the meantime.

    1. me-8 spark plugs are a drop in replacement for glow plugs. all that’s necessary is to add a magnet to the prop hub and affix the hall sensor at the proper location for a properly timed spark.

    2. there are spark plugs and ignition systems that you can add on, you attach a magnet to the flywheel and mount a hall effect sensor, then apply power to it and you’re basically done.

    1. we found the opposite to be true. gas and oil are not corrosive like methanol and nitromethane. our engines remain well lubricated from use and we don’t need afterrun oil like methanol fueled engines.

    2. Sorry Axeman, but obviously you are speaking from “I think it is like that” instead of actual real life experience.
      I do… I have been running Methanol engines on gasoline exclusively for the past 5 years.
      I have not been able to detect ANY wear, or deterioration of engine condition or performance.
      Most of my engines (cheap ASP clones, no less) have not even seen a single drop of methanol, they were broken in on gasoline straight from the factory.

      FWIW: I am the “Bert” from the top of this page.

      1. Interesting. Good to know!
        I wouldn’t have thought that it is so easy or even possible.
        What are the pros (other than the price of fuel)? Can you do it without this mixture controller and with standard carburetor?
        I would love to read an article about it. Maby you could write it on Hackaday?

        1. Compared to glow, the result will be an extremely easy starting and extremely reliable running engine with not only a cheaper fuel, but also a MUCH lower volumetric consumption (I have several planes that with the original tank size manage flighttimes of one hour or more).
          Plane usually remains much cleaner (really MUCH cleaner) but that last is a function of how well the user sets his fuel curve.

          It can be done with a standard carb if that carb is intended for heli engines, OR you can modify a standard plane-carb, but in both cases, cleanliness will suffer significantly.

          In the article on the top you will find a link to a thread in RCGroups that contains a lot of information. There is not a “single article” because it was 2+ years of developments and updates, progressing insights and gained knowledge, etc etc
          At the top you will also find a link to Dave’s github and wiki, where you can find a decent summary of how it all went down.

          1. Thank you!
            Very good summary. I’ve noticed the thread link in the article but over 250 pages of posts is quite a deep rabbit hole to go into. Free time is a scarse resource in my case.
            Still, this is new and interesting topic for me that I was not aware of. I guess I’ll stick to nitro for now (right, my engines haven’t seen fuel for years now but the kids are growing so maby I will resurrect my nitro car and plane). But some day… at the retirement…

          2. @ Vtech: Absorbing the info indeed is quite a bit. Look at Dave’s Github wiki, and you get the short and condensed version.
            Depending on your handywork skills, can’t tell how much time you need to build the controllers, but (assuming a built and functional plane) installing in a plane is an afternoon per plane including basic set-up. Finetuning can be done at the field.

    1. Well done!

      At long last, the zero wear, lasts forever internal combustion engine. Wait till the chainsaw people find this!
      Can these converted, ex-methanol engines run on gasoline without solenoids? Does the solenoid system also require feedback to and from the remote controlling transmitter?

      1. I never said “zero wear”, because that does not exist in mechanical stuff.
        I said that I could not establish any wear or deterioration. I am an engineer by profession. I am in modelling for 40 years. I am familiar with the normal deterioration of engines.

        No, the system does not use feedback (does not use actuall engine running parameters) to control the fuel, that is strictly a fixed relation between throttle position and fuel supply, just like any other regular carburation system.

        In my execution, it DOES however use telemetry data on ambient temp and pressure to determine the correction needed for changes in ambient conditions, that’s all. In Dave’s set-up, this is done internally in the onboard part of the system.

      2. this sounds like something gary cee/jessie open would say. he’s mentioned quite descriptively him in the source code. did you read the source code? it’ll tell you exactly how this system works.

  2. Interesting, zero wear alone is a remarkable achievement! Is it the solenoid control that accounts for the zero wear? I have watched people flying those glow plug engines start their engines. They often start with one flip, that part serms easy enough.

    1. Not zero wear. That is impossible. See my remark above: most defintiely LESS wear.
      Solenoid does nothing for wear and tear. Gasoline is a friendlier fuel, and the oils availlable for mixing with gasoline, simply are way better than the best availlable for mixing with Methanol.
      Obviously, you have never started glow engines yourself. If you would, you would know that single flip starts on glow do not happen by itself, it takes quite a bit of “feeling” and “familiarity with the particular engine” from the operator to achieve consistent single flip starts.

      Gasoline in that respect is much more consistent: “do this, then do that, and it will start”. I can tell a totally inexperienced guy how to do it and they will be succesful. I have sold gassers to “electrics only” flyers, and they could get along with their engine from day one. I have never seen that happen with glow.

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