I have 31 CC Ryobi weed trimmer engine I was going to use and I was wondering if converting it to a Glow engine would give a better power to weigh ratio vs gas. I lose about a pound of ignition related weight with a glow plus I don't have to worry about electrical noise.

Any other thoughts on advantages and disadvantages?

Dave

Dave,
With gas you have much less cleanup. You don't worry about hot fuel proofing. Gas is still cheaper. You can locate the tank on the CG. Fewer dead stick landings. Better fuel draw. You save on glow plugs. The prop hub is easy to get and cheaper. You don't have to add lead to the nose of many scale planes. You set the needles once a year rather then before each flight.

Dave

On the other hand...Glow will have more power and less weight. Oil will not cover your plane to bad because of the low amount of oil you will need in fuel. Tuning is not that bad once you get a ear for it. No radio interference is a REAL bonus. Capt,n Added..You can move the servoes ...receiver and battery forward for balance in most planes.

what percent oil is run in gas Weedie vs Glow or GGL 2:1GasGlow?

If I understand it, a gas 32:1 2stroke mix is around 3%, and GGL is around 3% (1/3 10%)
Wouldnt that mean similar amounts of goo on planes?

Yes and no. You are correct on your percentages. So less oil than normal glow operation means less oil on the plane. However, there's another factor. There is gasoline in the gas/glow mixture (obviously), and gasoline burns hotter than glow fuel. The oil in the mix burns. Therefore, there is very little, if any, glop to clean off the plane with either gasoline, or gas/glow operation provided the gas/glow mix is done properly. Some guys insist on doing the gas/glow with normal glow fuel. What you want to use is glow fuel for "Large Super Tigre" engines. It has only 10% oil to begin with, and that is what to mix with 2 parts of high test gasoline.

The advantages I have encountered with gas/glow are:

More power; usually a couple of hundred rpms
Easier starting
Smoother, lower idle
Less weight
Less worry of interference and component mounting

The only disadvantage for me, is that I have to run the engine out dry and use an after lubrication just like my normal glow engines, due to the fact that the engine is now running with alcohol and nitro in the mix, which can cause corrosion if left in the engine for any length of time.

AV8TOR

I was very skeptacal of the gas/glow mixture thing, but decided to try it. And now, I am a believer I mixed the 20/20, methanol, 91 octane gas ratios and ran it in my new SPE-26. Absolutly no black goo and excellant idle and transition/RPM. I cut 8 oz of ignition and battery. SPE-26 and muffler is now only 34 oz. (not bad for a 26 cc engine) and no concerns of interferance. I used a zenoah adapter and "hot" glow plug.

DaveW-
You posted your dislikes before I brought up the GGL 2:1GasGlow, how do you feel about that fuel rather than straight glow. Some of your points are still valid, but some are taken care of with the mix, & I dont want to pick at your post without letting you speak your peace on the GGL.

Full glow conversion will require twice the amount of fuel to fly the same amount of time as GAS/GLOW will, so with GAS/GLOW you are still taking advantage of gasoline without the heavy or expensive ignition system (if electronic ignition is used) besides gaining a little bit of power and smoother transition from idle to full power.

I have a Ryobi 31cc and want to get the best out of it for a 1/5 P51 and having read these posts I am keen to give this a try.
Exactly what do you do to convert to gas glow? Do you change the gas carby to a methanol ie OS type carby? and what is the fuel mix.
I imagine you put an adapter in the plug hole drilled and taped for a glow plug.
This is all new to me and would appretiate some advice.

cutarug

Horizon hobby sells an adapter for $10 that will reduce the spark plug hole for the glow plug.
Here is the link

http://www.horizonhobby.com/Stores/P...apter&CatId=EP

Dave

Hi Kid,
My comments were not dislikes. They were just points in favor of gas engines. I can make a list just as long in favor of glow engines. I like them all. I havn't tried GGL yet, the posted results indicate that it is the best solution for small gas engines. Larger gas engines have a good power to weight ratio, where the inverse is true when you get to the very small gas engines. It looks like GGL is the answer. The only negative is the need to do the mixing. GGL should even cut fuel costs on large glow engines, such as my ST3000. You just need to have the recommended percentage of oil. Bronze rod bearing are the problem. I thing GGL will allow the use of a Walbro carb also. I need to read some more.

Dave

DaveW-
You made a vary good point regarding the bronze bushing engines and the oil requirements, that is a hangup I have with a Glow--> GGL engine I'm planning. Now I'm glad I didnt just jump on you prior post


For a Gas --> GGL, while the GGL is much cheaper than glow fuel, it still has to use hot 4stroke glowplugs, and that aint cheap vs the occasional sparkplug in gas mode

HiKid,
That is a good point about the pricy hot plugs. This is a good reason to keep the compression close to stock to save on plugs. I can't think of anything in my first post that wasn't true.

Dave

I'm convinced its a good move but do you use the Walbro carby or will methanol attack the rubber.
Is the fuel 1 part methanol 2 -parts gas 30 : 1 oil content

DaveW- Could you explain some of these points further for the Advantage/Diasdvantage way the OP wanted
With a stock carb on a weedie with GGL (tuned to meter rich enough), what is with the Fuel Draw - which is also the Tank Placement line, I imagine.

But reconsiling the need to move the tank, with having to add nose weight..... move componants like tail servos & TANK to fix CG. Fly lighter. Lead is for Boat keels, not Plane cowls



Cutarug- the oil is plenty in the 10nitro-10oil glow fuel.... just add 2 parts Gasoline to 1 part 10/10 glow, not the standard 10%nitro with 18%oil glow fuel most .40engines use

Kid,
The Walbro has a pump that brings the fuel to the carb and then the venturi sucks it from the pump area. So the tank can be located on the CG. This eliminates CG shift due to tank level. The heavier Mag engine helps balance in short nose designs.

Dave

Dave for the Supertigre engines you can use regular 10% Nitro and 18% Oil and mix one part with 2 parts gasoline, this way will end up with 3.33% nitro and 6% oil which is the same oil content on the new Supertiger blend glow fuel made by one of the glow fuel manufacturers (Morgan glow fuels), another thing to consider is that gasoline isn't as dry as alcohol so it adds a little lubricity by itself thus requiring less oil than glow fuel.

Gas/Glow Fuel conversion consist in using a mixture of 10%Nitro 10% oil glow fuel mix in a 1 to 2 ratio with 91 octane gasoline (1 part of this glow fuel with 2 parts petrol) take note that this is a 10% oil content glow fuel blended for R/C nitro CARS this way you'll end up with a mixture of 3.33% Nitro, 3.33% oil, 26.33% Methanol and 67% Gasoline (aprox). If you can't get 10/10 glow fuel you can try the 20% nitro plane glow fuel blend and cut it to a 10% Nitro by mixing 1 part of the 20% glow fuel with 1 part methanol, you should end with almost the same formulation as the prior mixture but with 0.33% less oil (to me thats even better) this will end up giving you a 33:1 oil ratio in your fuel which is standard for the weedy engines I personally like 40-50:1 ratios.
As far as engine modification, these consist in adapting a 4 stroke glow plug via a glow plug adapter that you can purchase through Horizon Hobbies, you can use your walbro carb but need to lift a little bit just above the carburators body the regulator needle underneath the diaphragm, this is to let pass more fuel through every pulse, it doesn't damages your diaphragm gaskets or components.
The advantages of this system are as follows.
1. Save engine weight by removing the coil and flywheel (aprox 1 lb).
2. Gain power, about 500-800 rpms (this varies with the condition of the engine).
3. Better Idle and throtle transition from idle to full power.
4. Mantain the fuel economy of gasoline.
These are some of the advantages that I think are reason enough to convert.
So I hope this clarifies your doubts and questions about this system that we have perfectioned through our experimentation period and belive me once you try it you'll liket it so much that you,ll become a "GAS/GLOW CONVERT " for ever.

How about no worries about RF interferance You can locate radio equipment anywhere to suit.

aero nut

2 quetions

1) Can you explain by what you meant by lifting the carb a little bit. I am not sure I understand

2) What is the harm with running greater that a 3 % oil content other than more goo over the plane? If you use 18% oil like, in standard glow fuel, and mix per you recommendation you end up with 6% oil. That is still a big reduction.

Dave

aeronut I also am unsure about the mod to the diaphram
Check my JPG
Thanks for the explanation I get every thing else but the carby bit

This may help. Capt,n

Captinjohn

My assumption is you need to lift the needle higher to allow for more fuel flow through the carb. Since you have alcohol in the fuel you need more of it per stoke.

How much higher do you need to lift the diaphram and how do you accomplish this? Do you just bend the little lever?

Dave

Yup...Bend the little lever. Start at .010 Ten/thousandts of a inch very little. Capt,n

First, I recommend that you try the carburetor stock, (as is). Some carbs I have had to raise the lever a slight amount, others were fine without modification. If you can't get it to run rich enough without turning the needles out excessively, or if it won't get rich enough at all, then raise the lever a touch and try again.

The alcohol/nitro/oil mix in a standard glow engine burns cooler than gasoline. The oil itself doesn't burn, it just gets shot out the exhaust and blown all over the plane. Gasoline burns hotter, and most of the oil is burned with the gas. Therefore, if you run an excessive amount of oil in a gas engine, it will carbon up. This will cause problems with the glow plug in the short term, and ruin the engine in the long term. What happens is that eventually, the rings carbon up and stop moving in their lands, or grooves. Then hot combustion gases blow by the rings and burn the oil off the cylinder walls. The engine then seizes up, and it's good bye piston and cylinder, and if it happens on a low inverted pass, maybe good bye to an airplane! Please, use the mixture we came up with; it's a tiny bit heavy on the oil as it is.

AV8TOR