av8tor1977

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The airplane in my Avatar is an SR Batteries 1/3 scale Eindekker. 106" wingspan if I remember correctly. I powered it with a Honda GX31 four stroke. It had enough power to loop from level flight, but just barely. I ran the engine inverted and had no problems other than in storage, the oil would gradually run down and soak the plug, so I stored it with the airplane upside down and the spark plug upwards. The Honda engines have a special oil sump/system and can be run inverted; with the caveat being my above noted problem.

Yes, the Stihl Four Mix engines run oil in the gas like a two stroke, and have no oil sump/crankcase. What amazes me is that they are quite powerful for a four stroke. But they still have that cool four stroke sound, and fuel economy. I have a 36cc Stihl Four Mix all converted and "squirreled" away. Hopefully one day it will find a home on a Fokker D7. Should be a great combo!!

AV8TOR

SkyPilot101

Av8tor, did you use CDI on your 36cc fourmix? If so, it would be great to see a pic of the conversion. I'd like to do my 32cc and am guessing your 36 is very simular. Thank you

av8tor1977

My Feedback: (6)

Here's some pics of one of the 32cc Four Mix engines I did with magneto ignition. I don't have a pic of my 36cc engine with CDI ignition at the moment. If I have time, I'll post one tomorrow.

AV8TOR

Flight Risk

My Feedback: (1)

I would think that a 4 stroke conversion with gas/glow would work with on board glow battery. a little extra weight, but not like electronic ignition.

SkyPilot101

How about gas/glow on Ignition? I have a converted Stihl 32cc FourMix engine, and am thinking gas/glow fuel blend would up the power output, especially if a CDI conversion is made, and timing can be optimized. Anyone try this?

Flight Risk

My Feedback: (1)

It would be interesting to experiment with gas, methanol, nitro, and oil mix, with ignition. Then add nitrous oxide, and tuned pipe.
That brings up another question. Tuned pipes aren't very common on gassers, except on competition planes. The standard mufflers that come with gas engines have got to be less than optimal, as they are basically a box.

av8tor1977

My Feedback: (6)

Gas/Glow would work find used with ignition, though it somewhat defeats the original purpose of Gas/Glow, which was lighter overall installation, and cheaper.

And yes, it would add some power. Most of my Gas/Glow engines showed at least a 200 rpm gain, which is definitely noticeable on a 16 to 22 inch prop.

Nitrous Oxide wouldn't be very practical both because of the heavy high pressure tank needed, and the limited duration of the boost.

Tuned pipes work quite well on gassers and usually add 800 to 1000 rpms. Look into Macs Products. They have headers, tuned pipes, etc. for many engines. There are other sources too.... They aren't often used because they are long and bulky. Looks like a torpedo strapped underneath the plane!

AV8TOR

av8tor1977

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Sorry; double post. Darn website....

AV8TOR

fujiman

My Feedback: (133)

i just can't see why a gasser converted to gas glow wouldn't work, after all the big 4stk glow engs. are reliable enough and idle good. just mite have to up the alky content (with some ''heet'' additive) a bit to keep the glow plug lit. you could use onboard glow igniter at low revs. to make it more reliable. it would be fun to experiment a little and see if we could make it work and broaden our horizons.

av8tor1977

My Feedback: (6)

That's the jist of the possible problem as I see it. The Gas/Glow fuel mix only has approximately 30 percent methanol, and it is the catalytic reaction between the platinum in the glow plug and the methanol in the fuel that keeps the glow plug lit. A four stroke might work with Gas/Glow, but I think it would probably need on board glow power, at least at idle.

Hey, give it a try. Nothing to lose.... You might even try 15/10 fuel, as the nitro would also help keep the glow plug lit, and four strokes like nitro.

AV8TOR

fujiman

My Feedback: (133)

i agree plus you mite have to up the mix with more methanol (heet add. or racing methanol) plus on board glow liter. OS ''f'' plugs also stay lit better too. let's give it a go. can't see any probs. with it. i have a few 4stk twins and they have a prob. from time to time of 1 cyl. flaming out so i always run on board glow liter at idle or any position that keeps things going. we mite have to lower the gas and up the methanol and oil. and then add a little acetone to keep things mixed.

Flight Risk

My Feedback: (1)

Could an engine run on pure gas (and oil), if it had constant on-board glow? Probably would need a good size battery.[X(]

av8tor1977

My Feedback: (6)

There was one guy here in the forum that was doing just that, and he said it ran good. I think I tried it once and wasn't happy with it. Yes, you would need a good battery, as a glow plug pulls around 3 amps....

AV8TOR

fatcharlie

This is sooooo interesting!

As far as I understand, a 2stk gasser can quite easily run on 2:1. That would be 2 parts Gas to 1 part 10/10 Glow Fuel, and that the plug has no problem staying lit.

The issue with a 4stk gasser is that the plug is less likely to stay lit if run as a gas/glow, because the methanol content is not enough., and it's the reaction between the methanol and the platinum in the plug which keeps it lit.

Since the Methanol content in this scenario is the same as for a 2stk, I assume the issue is because the 4stk is firing less often, so in any given time, the methanol supply is only half that of a 2stk, plus the heat supply is halved as well in the same time period.

So, we can easily double the methanol supply, by changing the glow fuel content, i.e. 1:2, Gas to Glow Fuel. To avoid smokiness, perhaps the oil content of the Glow Fuel could be reduced.

As regards the heat, onboard glow is a possibility I guess, but adds weight.

Many people have mentioned that gas/glow engines run a little cool - a few have reduced the size of cooling fins to compensate. I seem to remember it's something in the fuel which does this.

What is it that keeps the engine cooler, and could that be played-with in the fuel mix to keep thngs hotter in there?

I am by no means an engineer and would never claim to be, but it seems there is lattitude for experimentation with a 4stk gasser, to run it on gas/glow without need for onboard glow, negating the need for the extra weight, complexity etc.

It seems plausible that this could be achieved simply by playing with the fuel mix.

How about 1:1 gas to glow, reduding the oil and nitro in the glow to keep the overall oil/nitro content the same? That would nearly double the methanol content.

Does that make sense?

Best to all,

Roger.

av8tor1977

My Feedback: (6)

All your deductions are correct. The reason a methanol fuel runs cooler is because of its latent heat of evaporation and also the fact that an engine needs more methanol than it does gasoline. A richer engine of course runs cooler.

I would try using the original formula Gas/Glow fuel mix first, being sure of course, to use a good quality four stroke glow plug such as the OS "F" plug. For a custom "Four Stroke Gas/Glow Fuel Mix" you mention lowering the oil content in the glow fuel and raising the methanol content. The only way one could do this would be to buy the separate components of glow fuel, and custom mix them. Methanol, Nitro, oil, etc.

Sorry I just don't have time to experiment myself with all this, but will be very interested in hearing the results of your experimentation.

Good luck and have fun,
AV8TOR

fatcharlie

Hi Av8tor,

Not experimenting yet - just conjecturing. I don't even have an engine yet :-)

But I'll let you know how things go when I do.

One thing; if it's the methanol which makes the engine run cooler, then upping the proportion of methanol in the fule mix, to keep the plug lit, would probably make it run even cooler, right?

Cheers,

Roger.

av8tor1977

My Feedback: (6)

Probably, though it depends how high you go with the methanol percentage. A small change might not be noticeable.

Something you might run into if you get the methanol mix very high, is that the carb then won't flow enough fuel. An engine needs approximately twice the amount of methanol to run as gasoline, and as you increase the methanol content, the carb will have to flow more to maintain a proper air/fuel ratio. The Walbro WT-499 carb is made for alcohol use and has larger internal passages to flow more fuel. Other carbs can have the passages drilled out, but it is a tricky business if you don't know exactly what you are doing and it is easy to ruin a carb... Since the WT-499 isn't made for a four stroke, you might have to use a spring in the fuel pump chamber to get it to pump fuel properly when used on a four stroke.

AV8TOR

Flight Risk

My Feedback: (1)

And a 4-stroke should require less fuel than a 2-stroke, so maybe just using a 2 stroke carb, if there is such a thing. How about using a carb off a glow engine, and pressurizing the tank?

av8tor1977

My Feedback: (6)

Glow carbs don't work as well as the Zama and Walbro carbs for gas because they are designed for methanol flow and are really critical in adjustment when used in a gasoline application. Besides, the pumped and regulated Walbro type carbs are nice to use and a definite step up from the very simple glow type carb.

As I mentioned, I have no personal experience with gas four strokes converted to Gas/Glow. I am just throwing things out there as they occur to me; things to be aware of, and some of them may not turn out to be an issue, while others might. But being armed with as much knowledge and shared experience as possible makes experimentation easier and less nerve wracking...

AV8TOR

fatcharlie

Hi Av8tor.

As before, thanks for the insight and observations - i agree totally that it helps focus the experimentation into a more coherent effort.

As regards Walbro carbs, I had a look at their website. I think the two types with Butterfly valves most suitable for our purposes are the WA/WT series and the HD series for larger engines. I note the only main difference in the blurb seems to be the WA/WT series has a prime/purge function which isn't mentioned on the HD's.

In Rotary valve carbs, the WY series has a plethora of choices, too complicated for me to see which would be best.

Does anyone have any experience with these types? they are obviously the lates versions - perhaps people have been using s/h versions?

All very interesting.

Thanks,

Roger.

PS Just seen you have been using the Walbro WT499

av8tor1977

My Feedback: (6)

No, I haven't been using the WT-499. I have one, but haven't needed it as yet. With all the Gas/Glow conversions I have done, the most I have had to do is raise the regulator lever a bit to get the carb to go rich enough for use with the Gas/Glow fuel. I've even got a 48cc twin that I made running on Gas/Glow with just a WT carb.

There is a WYK carb that has twin adjustment needles ,(many of the WY series carbs don't have twin adjustment needles, and having them is absolutely mandatory), and seems to work well on four strokes, but unfortunately I don't have the number. Maybe someone will jump in here and let us know.

Well, here is one I found, but I don't know if it is the one the other guys playing with four strokes are using. You might do a "WYK" search here in the forum.

www.davesmotors.com/s.nl/it.A/id.4132/.f

AV8TOR

av8tor1977

My Feedback: (6)

Home made 48cc twin running on Gas/Glow.



AV8TOR

av8tor1977

My Feedback: (6)

Sorry these pics took a while. Stihl 36cc Four Mix with electronic ignition. (The 32's and 36's look identical from the outside.) I used one of the round style sensors like CH Ignitions used to have. If you can't buy them, you can make them from an RCEXL sensor, some tubing and some glue.

One could probably just mount an angle bracket of some type off the crankcase screw, but I think my way looks better. I made that piece of aluminum block to go in between two crankcase webs, bolted it there, and then drilled and tapped that block to hold a home made sensor tube bracket.

The pics embarrass me a bit because of the rust. I live near the beach and the salt air here is like "acid"!!!

AV8TOR

the Wasp

My Feedback: (1)

hey guys,, I need a Glow Plug adapter for me Zenoah 20,, anyone know where I can get one ???

Jim

fujiman

My Feedback: (133)

hi wasp, i make them send me a privet mess. for info. also you can check out my ad in the buy/sell section under gasoline engines