I've got a 26cc Ryobi four stroke, and was wondering if it would be possible to run it purely on methanol. Since it has its own sump, it wouldn't need oil in the mixture, and a glow plug would allow it to run without an ignition, thereby either eliminating the weight of a magneto, or the cost and complexity of electronic ignition. Bulk methanol is not very expensive either... Any thoughts? How would it compare in consumption and power to gasoline?

Hi
gas runs on a fuel air ratio of about 15 to 1 the alky runs on about 8 to 1 or it takes about twice the amount of alky to run the same eng. the alky has fewer btu.s per pound but with the higher consumption produces more heat per hour. about 10 to 15% more power on alky. but it is a cleaner burning fuel. clear as mud ?

gas acts like a lubricant , methanol is very dry I would mix in a little oil like 100 to 1 just for upper ring lube.

Darin

IIRC, the Ryobi 26cc 4stroke has three rings - two for compression and one for oil control. This means you probably don't need to worry about blowbys contaminating the oil sump. But like Darin said, I would worry a bit about upper cylinder lubrication.

Your biggest problem, however, is finding a carb that'll fit on the intake manifold and flow enough fuel for methanol. I haven't broken mine out yet, but those that have say the crankcase tap hole location is not compatible with the common Walbro WT and WA carbs.

It's an interesting idea though.

I'm primarily trying to reduce weight at this point. Not having an ignition system wouldn't hurt that goal. It would reduce complexity substantially as well, and eliminate a significant amount of radio interferance. If it burns twice as much fuel it isn't going to be a very good solution for economy, which is my ultimate goal. As light as possible, and for as long as possible. Making the manifold wouldn't be a problem, but how do you mount a glow plug?

Hi
Yes carb. with enough flow capacity is a problem, but you also have to be careful as many gasket materials are not compatable with alky. When gas with alky first hit the market many carbs. had to be rebuilt due to this problem. I don't want to sound to down the upside is a motor run a racing season on alky would be clean like new when you tore it down. Also alky has a octain rating around 220 so almost unlimited compression. but on these motors can't get that kind of compression. its to bad to as it gives power throughout the rpn range.

I belive CH ignitions make or have adaptors not pos. on this one though

they do, but the battery life isn't really long enough for what I'd like to do. A big enough battery is weight prohibitive. I'd like to be able to keep this thing in the air several hours for endurance flying. You get to the point where a battery that big weighs the same as a magneto. The ideal solution would be no ignition system, and low fuel consumption, and low overall weight. It sounds like I would more than offset the weight savings of no ignition with extra fuel.

Sometime back I believe it was sullivan ( the fueltank people) made as small gen. for Rc that basicly gave infinate flite time it was as I remeber fairly lite and small

Yup, the sullivan genesys. I've looked at it, and would prefer to not go that route if possible. It might not be.

I think post #7 is talking about a glow plug adapter to go into the spark plug hole. Yes, CH Electronics does sell them; I bought several from them.

I wouldn't worry too much about burning too much methanol. The way I've seen my Ryobi 4stroke sip fuel, twice as much of VERY LITTLE is still VERY LITTLE.

I think you'll end up saving some weight and gaining a good bit of power, if done right. I've converted several weedies to glow, and they've all run well and end up significantly lighter.

"I wouldn't worry too much about burning too much methanol. The way I've seen my Ryobi 4stroke sip fuel, twice as much of VERY LITTLE is still VERY LITTLE. "

but let's say that in a normal setup (not for several hours flying time) you would use an 8oz tank for gas or at least a 16oz tank for methanol, right? thats already a 10oz difference (remember that gas weighs less per fluid ounce) that could be used for ignition. now for batteries you could use duracell 3 volt lithiums that weigh 17g each, a pack of 4 would make a 6 volt, 3400 milliamp battery of only 2.5oz. add to this 4oz for ignition and the gas burner is already at an advantage, start adding fuel for an endurance flight and gas will have a huge advantage.

now maybe you could mount the ignition sensor to the cam instead of the crank and save the wasted spark and in turn draw less amps from the battery. that 3400 milliamps would probably give about 12 hours flying time. you would also have the reliability of the ignition system.

dave

From what I have heard, the ryobi uses about 12 oz of fuel per hour at 7000 RPM. It doesn't take much fuel to outweigh the magneto. I hadn't looked at Li-Ion, though that is a simple possibility. I do have an Orbit Microloader that would charge them. And timing off the cam sounds like it could work, and would cut consumption by almost half. I'm already going to have significant battery load for the RX to last that long. Thanks for the idea.

The SG of gasoline is 0.69; methanol is 0.79. 8 fluid Oz. of gasoline weighs 5.5 Oz. 16 fluid Oz. of methanol weighs 12.6 Oz. So the difference would be ~7 Oz. I think the flywheel alone weighs far more than that.

This is not to mention the power gain of using methanol. 800rpm gain with an 18x8 is probably not out of the question. That's about how much a G23 or G26 gains with methanol. That's a gain of more than 3 lbs of thrust. This means that glow fuel can fly the same plane at the same speed at a lower throttle setting - burning a little less fuel in the process.

I'm not necessarily a proponent of gasoline-to-glow conversion. Most of my conversions are still gasoline powered, all of which are using CH Ignitions. But Jcadwell asked about the feasibility of glow conversion for this particular engine. So, I tried to answer the glow fuel question directly without coloring it with my own preferences.

oops! was thinking that meth has an sg of 1, my mistake.

for normal flight times glow does have an awesome power advantage (if you can afford it) but for several hours in the air you simply can't beat gas. the main reasons i fly gas are economy and reliability.

dave

the stock flywheel weighs 9.5oz. and the whole ignition setup weighs 17.25oz.

I would definitely mount the magnet/hall sensor on the flywheel and use lithium/polymer batteries. Since each L/P cells is 3.7v, two would be 7.4v and require a voltage regulator. The capacities on those batteries is fantastic and they are very light. Just make sure you use the correct charger and don't discharge them too fast.

For glow use....try a carb off a satio 1.8 4 stroke...let us know how you are doing. Thanks Captinjohn

The answer for your problem is to stay with gasoline, but switch the spark plug to a "Smart Plug".

www.smartplugs.com

Although somewhat $$, they don't require an ignition source, and you get the fuel economy of gasoline. I see they've recently added a 4-stroke Ryobi to their list of tested engines...

* No Distributor, Coil, Points or Moving Parts
* No Modification to Engine Necessary
* Ignites a Variety of Fuels (proven with Gasoline, Diesel, Bio Diesel, Jet A, JP 5, JP 8, Propane, Methane, Nitromethane, Methanol, Ethanol, Hydrogen, Naphtha, Reclaimed Tire Oil, Aqueous Fuels)
* No Electrical Noise
* No High Voltage
* Non-fouling
* Faster Burn
* Cleaner Burn
* Less Detonation
* Moisture Insensitive
* Can be used on a variety of engines (4-Stroke, 2-Stroke, Rotary, etc...)
* Exceptionally High Altitude Capabilities
* Cold Starts Better than a Standard Spark Ignition System

They have even tested it with an RC engine (ASP 2-stroke on glow fuel) http://www.smartplugs.com/engines/2stroke/asp.htm