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Old Jan 18, 2013, 09:07 PM
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Besides cost, is there any reason to use glow over gas?

Getting back into the hobby and seeing a lot of the smaller gas engines out now. I hate glow residue and the cost of fuel as well as the glow ignitions. I've got 4 glow engines leftover from the late 90s that I'm going to use to get back into the hobby but after that I'm not sure. Is there really any advantage at all besides cost? I mean a 1.20 4 stroke gas is VERY expensive compared to something like a 1.20 glow but still...
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Old Jan 19, 2013, 02:58 AM
supreme being of leisure
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Tel Aviv, Israel
Joined Jul 2004
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other than cost (and that really depends), gas is all cons:

it stinks

it goes bad after a while and then REALLY stinks

it makes a lot less power

it runs much hotter

------------------------------------------------

best of both worlds is to add ignition to a glow engine and run methanol/oil mix...you get the reliability of ignition and depending on the engine, power can equal or exceed what glow ignition does. no wonky walbro carb to piddle with. depending on where you get the methanol it can cost about the same as running gas...and even if it costs a bit more it'll still be way cheaper than off the shelf glow fuel and still a drop in the bucket compared to every other thing in the hobby.
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Old Jan 19, 2013, 06:59 AM
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You mean a glow driver like this?

I'll have to google on how to run methanol/oil, you mean E85 correct? Unfortunately there aren't any of those in NJ or if there are they aren't around here.

I was also not aware that something like a Saito 1.26 would make less power than a comparable OS 1.20 Surpass, both being 4 strokes. Reason? As far as fuel going bad, there is always the option to dump old fuel into the lawnmower tank.
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Old Jan 19, 2013, 07:26 AM
WCB
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I like gas because it is more convenient. No glow starter to fool with and since I hand start my gassers I don't need to haul an electric starter and battery. When I get done flying I don't have a gooey mess all over my plane so it doesn't take much effort to clean them. Gas engines seem to be less sensitive to temperature changes so I don't have to tune as much. Once I get the needles set right I seldom have to mess with them again unless I change something like a prop or oil mixture.
I do love to smell that castor oil with a glo engine though. Takes me back to my line control days.
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Old Jan 19, 2013, 07:55 AM
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Yes, there are still several good reasons to stick to Glow.
-For starters, the engines are much lighter for the same power output.
-They are availlable in smaller sizes, and properly adjusted, they are just as reliable (theoretically one might argue they are even more reliable because there are less essential parts that can fail, like ignition, pressure regulators or carbs, etc etc, but that is merely theoretical)
-For modelling, the technology of glow has matured more, small gassers (say, below .90) are still "under development" more or less
-the gunk from glow is nasty, but the gunk from gas is black and very sticky, so here it is basically one nasty thing for another
-If, as Zagnut suggests (and as I have tested in the recent past and I am VERY happy with the results) you fit ignition but stick to methanol, you have best of both worlds: fuel economy that comes close enough to running gas because you can get rid of Nitro and consumption is up to 25% (roughly) lower than with glow. Unfortunately there is a slight weight penalty and you need to fit sensor and magnet to your engine yourself.
-The engines produce significantly lower vibration levels than purpose designed gassers.

All in all, for me more than plenty good reasons for me to stick with "glow" engines (with or without spark ignition).

Brgds, Bert
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Last edited by Brutus1967; Jan 19, 2013 at 01:34 PM. Reason: Mixed up two Israelis.... apologies!
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Old Jan 19, 2013, 08:01 AM
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Well besides what is mentioned already, a glow engine doesn't need an ignition module and battery to work. A glow engine is very simple in comparison to a glow engine. That simplicity is what makes glow engines so popular, in spite of them being more messy. The carburetor can be much more simple. The glow engines do not carbon up like gas engines either. Small gas engines can be almost as messy as glow engines as the small gas engines still need lots of oil in the fuel and it doesn't all burn up leaving the engine either.

But a good 15cc to 20cc gas with a needle bearing connecting rod can typically use 32:1 or even 40:1 or maybe 50:1 in some cases of oil to fuel ratios and as such doesn't leave hardly any exhaust residue to clean up. The smaller 9cc and 10cc gas engines are still relatively new on the market, but they still need 20:1 to 25:1 oil to fuel ratios and as thus more messy, but not as messy as a same size glow engine though. Then the bigger gas engines 30cc on up to 150cc or more tend to use 32:1 to 50:1 oil ratios and can be quite clean running in comparison to big glow engines.

As to power, a glow engine develops more power than the same size gas engine. Thus to equalize the power, one has to increase the displacement of the gas engine to compensate. One can use the same method that they use between two stroke glow engines and four stroke glow engines. Thus a two stroke .60 glow engine would need a .90 to 1.20 size four stroke engine to get the same equivalent power. So a gas engine equivalent for a .60 engine would be a .90 to 1.20 size gas engine (15cc to 20cc).

Now then those people who do not like cleaning their airplanes after using them, tend to gravitate to electric power instead. Electrics are clean, easy to start, easy to run and leave no messy residue behind after running the electric motor.
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Old Jan 19, 2013, 10:55 AM
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Glow engines are super simple. What 3 moving parts.
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Old Jan 19, 2013, 11:05 AM
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Quote:
Originally Posted by ZAGNUT View Post

no wonky walbro carb to piddle with.
I have to agree with you there.

Those Walbros are still a mystery to me.
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Old Jan 19, 2013, 11:58 AM
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Committing only to glow may restrict you to certain sized planes. Although I guess there are some great large electric motors any more...

You don't see many 40% planes with glow engines!
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Old Jan 19, 2013, 12:54 PM
supreme being of leisure
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Tel Aviv, Israel
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Quote:
Originally Posted by scottydsntknow View Post
You mean a glow driver like this?

I'll have to google on how to run methanol/oil, you mean E85 correct? Unfortunately there aren't any of those in NJ or if there are they aren't around here.

I was also not aware that something like a Saito 1.26 would make less power than a comparable OS 1.20 Surpass, both being 4 strokes. Reason? As far as fuel going bad, there is always the option to dump old fuel into the lawnmower tank.
no, i'm talking about real spark ignition or "CDI". CH seems like the go-to place for everything needed to convert a lot of engines.

and E85 is ethanol not methanol although just about anything will work with CDI. nice thing about good old methanol is that it's not compounded from 2 dozen different chemicals so it basically has an infinite shelf life...i'm betting E85 doesn't fare any better than gasoline.

and i don't know about saito vs. OS but methanol makes more power than gas, especially when you have real control over the ignition timing like with CDI.
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Old Jan 19, 2013, 02:35 PM
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Originally Posted by 4075aaron View Post
Committing only to glow may restrict you to certain sized planes. Although I guess there are some great large electric motors any more...

You don't see many 40% planes with glow engines!
I do love the way the radial glow engines sound but omfg they are expensive. $4k a pop... I can build a forged shortblock for my Mustang for less than that haha.
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Old Jan 19, 2013, 03:01 PM
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Originally Posted by scottydsntknow View Post
I do love the way the radial glow engines sound but omfg they are expensive. $4k a pop... I can build a forged shortblock for my Mustang for less than that haha.
Ya.... you probably could....

Not many airplane kits one of those will fit on though....

Brgds, Bert
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Old Jan 19, 2013, 06:49 PM
I HATE GLOW PLUGS!
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Why not have the best of both worlds & run CDI W/glow fuel?

All the user friendly advantages of gas W/O the smell.

5-6% More power than glow ignition (22-24% more power than gas) W/O a seperate voltage battery or glow driver. No kicking back, easy one flip starts. 25% longer run time on a given amount of fuel.

If you are a tinkerer, you can run very high compression ratios W/CDI burning methanol based fuel.

I put togeter a 12.77:1 compression version of the FA180 that will turn an 18 X 8 prop @ 8850 RPM!

4HP & 23# of static thrust from a Saito FA180 4-stroke.

If you are considering on board glow just spend a bit more & get a CDI. Onboard glow is a waste of $$$ as CDI will pay for itself in a season W/fuel savings in a medium/large engine.
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Old Jan 20, 2013, 04:35 AM
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Originally Posted by SrTelemaster View Post
Why not have the best of both worlds & run CDI W/glow fuel?

All the user friendly advantages of gas W/O the smell.

5-6% More power than glow ignition (22-24% more power than gas) W/O a seperate voltage battery or glow driver. No kicking back, easy one flip starts. 25% longer run time on a given amount of fuel.

If you are a tinkerer, you can run very high compression ratios W/CDI burning methanol based fuel.

I put togeter a 12.77:1 compression version of the FA180 that will turn an 18 X 8 prop @ 8850 RPM!

4HP & 23# of static thrust from a Saito FA180 4-stroke.

If you are considering on board glow just spend a bit more & get a CDI. Onboard glow is a waste of $$$ as CDI will pay for itself in a season W/fuel savings in a medium/large engine.
I am not a tinkerer, do not run high compression ratios and are not looking for the highest power, but all other advantages in the above post, I can confirm:
Leaner running without overheating, easier starting, lower fuel consumption and (without tinkering and modifying, just proper carb adjustment) higher power output.
The fact that you can completely get rid of the Nitro, lowers the fuel bill even more, and gives even longer runtimes (that is, if you was using Nitro in the first place.

One thing I have discovered though: in cases, it might be necessary to increase the oil content.
My OS was running on 10% Nitro, 10% oil, and after conversion to spark engine, and leaving out the Nitro, I needed to raise the oil content by 2% in order to keep the same amount of oil through the engine.
I did not do that "just on a gut feeling", I actually noted that with 10% oil and no Nitro, I had to lean out the engine so much that lubrication became too little and it actually lost power a bit. I either had to run it too rich or it ran too hot, could not get the mixture "spot-o".
Adding the 2% extra oil made the engine run like before the conversion, but with noticeable more power and consistency.
Other thing I noted was that on glow, 10% Nitro and 10% oil the oil coming from the breather was pretty much amber coloured (new oil is as clear as water) and with spark, and 0% Nitro, regardless of 10, 12 or 15% oil, the oil is much less discoloured compared to the Nitro fuel/glow ignition.

I do not know if this is because of the Nitro, or because of the influence of the spark on the combustion process.

I have also modified a 2-stroke that has always run without Nitro, and here I noted that the oil coming from the exhaust looked lighter, clearer and cleaner too.

It leads me to believe, that spark ignition is friendlier on the oil, leaving more of its lubricating properties intact during its journey through the engine.

However, I have no way of investigating, confirming or proving this. It's just a hunch....
I have the feeling, that because the ignition timing is more constant and the start of the ignition is sharply defined, the combustion process stays cooler (no pre-ignition) and more constant, reducing the amount of oil being burned/decomposed.
Maybe one of the experts can say something about this?

Brgds, Bert
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Old Jan 20, 2013, 07:47 AM
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Originally Posted by ZAGNUT View Post
no, i'm talking about real spark ignition or "CDI". CH seems like the go-to place for everything needed to convert a lot of engines.

and E85 is ethanol not methanol although just about anything will work with CDI. nice thing about good old methanol is that it's not compounded from 2 dozen different chemicals so it basically has an infinite shelf life...i'm betting E85 doesn't fare any better than gasoline.

and i don't know about saito vs. OS but methanol makes more power than gas, especially when you have real control over the ignition timing like with CDI.
I do'nt agree on that infinite shelf life. Recently did open a brandnew-sealed glowfuel can that was about 6 years old and noticed it had turned very dark in colour, used it to run in an OS fourstroke and got hit very hard on a thankfully heavy duty glove protected starting hand, so hard it did brake the Graupner gray nylon prop when the engine kicked back. Lesson learned to use only fresh glow fuel !
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