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-   -   gas fuel with glo plug no ignition (http://www.rcuniverse.com/forum/engine-conversions-92/1267448-gas-fuel-glo-plug-no-ignition.html)

aero nut 11-10-2003 09:46 PM

gas fuel with glo plug no ignition
Hi fellow converts, I am new to the conversion addiction, and after a few conversions I tried a gas engine with a glow plug and gasoline with 50:50 oil ratio (synthetic oil) the engine is a weedeater 18 cc and the ignition was removed, but first I runned the engine with the regular magnet ignition and it turned 7500 rpm's with a 15-8 master airscrew prop,
then I ran the same engine with a glow plug adapter and without the magnetic ignition, the glow plug was kept hot with two 1800 mah metal hidride batteries and the reading on the tach said 7450 rpm's; we then removed the battery while it was running and the rpm's droped about 700 rpm's.
Has anybody tryed this configuration.
Perhaps we can use something to make the gasoline a little bit hotter and keep the glow plug burning better.
Any Ideas or input on the matter.

mdavies31 11-10-2003 10:10 PM

RE: gas fuel with glo plug no ignition
You say 50:50 oil ratio, do you mean 50 to 1 gas to oil or 1 to 1 gas to oil?
If it is 1 to 1 that is way to much oil. 50 to 1 is good.
What glow plug are you using, is there a hotter one? Is the adapter getting the plug into the engine as far as the spark plug went?
Could you use a on board glow driver with a small, light weight battery that only is on at full throttle?

aero nut 11-10-2003 11:47 PM

RE: gas fuel with glo plug no ignition
you are right the oil content is a 50:1 ratio; The adapter for the plug was made out of a spark plug to which al the ceramic and electrode was removed then it was tapped with a glow plug tap(1/4, 32) and the plug just comes flush with the bottom of the adapter; the plug we used at the moment was a hobby people's thunderbolt # 3 plug which has a heavier coil, maybe a std rc plug will work better?.
As far as the the onbord system goes we found out that the engine would stop running at idle if the battery was removed.
I was also thinking Hiher comprension ratio perhaps, Higher octane fuel aviation fuel or racing fuel? and use of amsoil for a 100:1 ratio mix.

mdavies31 11-11-2003 12:04 AM

RE: gas fuel with glo plug no ignition
I don't know thunderbolt plug's but a OS #3 is supposed to be their hottest plug.
I was concerned that the adapter held the plug to high and reduced compression a little but it sounds like it about the same a spark plug.
Gas has less BTU's then alcohol, less BTU's = less power.
With out the battery to keep the plug hot I don't think it will work.

bn120 11-11-2003 12:48 AM

RE: gas fuel with glo plug no ignition
I never tried a glow plug with gasoline I thought it would not work, huh guess I was wrong, so why are people using electronic ign. just use a glow plug, gas and a remote glow system?

bn120 11-11-2003 12:54 AM

RE: gas fuel with glo plug no ignition
try a os #F plug for the four strokes they are verry hot and has a thick element to keep it warm enough to go through 4 clcles.


h82crash 11-11-2003 01:48 AM

RE: gas fuel with glo plug no ignition
The theory goes; methanol reacts with the glow element to keep it hot. I've read stories about people starting their glow engine without a glow battery attached. That behind us, sounds like gas will run with an on board glow system.

mdavies31 11-11-2003 12:05 PM

RE: gas fuel with glo plug no ignition
I've been think about what bn120 said, why do we have spark type systems and I got the answer.
With a spark ignition the plug fires at whatever degrees before top dead center its supposed to but with a glow plug it fires when it wants to. I think thats why you lost rpm with glow and a battery, its firing at less degrees BTDC and even less without the battery because the plug cools off and takes longer to ignite the gas.
His idea about the four stroke plug should help but without any way to control when it fires you may never get to same RPM as a spark plug.
h82 crash is right, I had a GMS .47 start with out a battery, I was flipping it prior to attaching the glow driver to clear it of extra fuel and it started. Woke me right up, glad I was using a chicken stick.

bn120 11-11-2003 08:07 PM

RE: gas fuel with glo plug no ignition
if in facyt it will run on gas then you could control the timing by the heat applied to the plug 1.5 volts would be hotter than 1 volt so it should fire sooner.whatcha thinks? if this does indeed work I will make all my conversions with a 3 volt pack with a petentiometer to adjust the heat(timing)you could always use the glow driver from a power panel you can adjust the heat it and see if it works.


ps. keep us posted ,this would really be the ticket for alot of people.

wvarn1957 11-12-2003 11:04 AM

RE: gas fuel with glo plug no ignition
The platinum on the glow plug element is a catalyst which initiates the oxidation(combustion) of the fuel. Platinum is a very common component of catalysts used in the petrochemical and refining industries. It will initiate the oxidation of most any organic in the vapor phase. The rate of combustion is dependent on the specific compound, pressure and temperature. Consequently, gasoline can be used, but consistent performance could be problematic.

Because glow fuel is essentially a single component fuel, it works well in IC engines using catalytic combustion initiation. As a result ignition timing will be consistent. Gasoline, on the other hand, is a multi-component fuel and because of EPA's Air Quality regulations is blended for specific areas and for specific seasonal considerations. Consequently the component mix is constantantly changing. In an IC engine which uses spark initiated ignition, this is not a factor in ignition timing. However in an IC engine dependent upon catalytic initiation, the ignition timing is affected by the varation in composition.

There are several ways to minimize this variation in gasoline blends and get somewhat more consistent timing. Using 100 octane low lead Aviation gasoline would be much more consistent than automotive gasoline, since Avgas blends are very consistent from area to area and season to season to season. In additon, using 15% to 20% methanol or ethanol would improve the timing consistency. Other things such as acetone, MEKP, butane or ether would help, but that is getting pretty exotic in mixing techniques and increases the hazard potential of handeling the mixes.

Increasing or decreasing the compression will also affect the ignition timing. Generally lowering the compressing would have the effect of retarding the timing,while increasing the compression would have the effect of advancing the timing.

In addition the idea of varying the tempature of the glow element by varing the amperage will have some effect on the timing, but I wouldn't hazard a guess as to whether or not this would mitigate the impact of the composition variation of gasoline.

I would like to correct a statement that was made in a previous post on the comparison of methanol and gasoline. Methanol, depending on its purity, has a heat content of 8,000 - 9,000 BTU/lb. Ethanol has 11.000-12,000 and typical gasoline blends have 18,000-20-000 BTU/lb. Air to fuel ratios for methanol, ethanol and gasoline are (approximate) 6.5/1, 9/1 and 14.5/1 respectively. An IC engine burning gasoline will run quite a bit hotter than an IC engine burning methanol because of the difference in the latent heats of vaporization.

Antique 11-12-2003 12:31 PM

RE: gas fuel with glo plug no ignition
Buy a gallon of methanol, mix it with synthetic oil at 50-1 like a chainsaw, use a glow plug..No problems....Methanol is not than much more expensive., around here it's around $2.00 a gallon....
You will use about twice as much fuel and the carb will need to be modified for straight methanol...

foamcutter 11-12-2003 01:26 PM

RE: gas fuel with glo plug no ignition

What type of modifications to the carb are you suggesting? Bigger carb?

Thanks, Ron

Antique 11-12-2003 02:06 PM

RE: gas fuel with glo plug no ignition
Bigger carb is not necessary..Some carbs will work with either fuel, but most need to have the fuel passages enlarged..The main inlet hole, under the inlet needle, is drilled out to .083..All the other holes are doubled in AREA, not DIAMETER..This makes the carb work exactly the same as is does with gasoline..
The Walbro WT499 from a glow G23 works just as well with gasoline as it does with methanol..I put a WT499 on a G26, ran it with gas, got 9000 rpm..Put in a glow plug, changed to glow fuel, turned 9600 rpm..The engine idled and transitioned the same either way...The glow fuel was old so the % of nitro was unknown, probably 15%......

aero nut 11-12-2003 04:11 PM

RE: gas fuel with glo plug no ignition
Thanks everybody for all the input I am receiving, it is a lot of fun and educational at the same time, the next step on this project will be trying
the methanol:gasoline blend in a perhaps 10 to 20 percent range also I will try to get some Amsoil I heard that it works real good even on a 100:1
mix ratio which it means less contents of oil, cleaner buring more power, switch to a four stroke plug and see what happens.
Iwill also be thinkering with avgas and the pure methanol version, I am convinced that we can do something to improve this and saves us some weight and MONEY.
I would like for some of you guys to try this configuration so we can compare results and get to some conclusions, this would be a lot of fun and interesting.
Thanks. Bill Pomplun.
P.S. By the way my club is located in Tijuana Baja California Mexico so once again you can say that R/C modeling is UNIVERSAL.

bn120 11-12-2003 10:16 PM

RE: gas fuel with glo plug no ignition
will methanol and gas mix? I know amsoil will not mix with methanol.klotz oil will mix with both.


bn120 11-12-2003 10:23 PM

RE: gas fuel with glo plug no ignition
oh 1 more thing you might want to check out is coleman fuel it is white gas less odor and has a lower octane rating and more pure and consistant.

av8tor1977 11-13-2003 09:37 AM

RE: gas fuel with glo plug no ignition
VERY interesting dissertation by wvarn1957-RCU, and we thank you. One point however... I'm afraid that the high lead content in aviation 100LL could be a problem in our low compression engines. Generally, unless the engine has enough compression, (and heat of combustion) to need the lead for detonation suppression, the lead causes spark plug fouling. This has been a major problem in the airplanes designed for 80/87 octane, that were forced to use the 100LL after the older fuel was phased out. I think this could be a problem with our model engines, with the lead fouling the glow plug, and/or causing a lot of carbon build up. Other opinions???

wvarn1957-RCU, if you were to mix some acetone with gasoline to enhance the catalytic reaction, what ratio would you use? If you were going to try this, what would your recommended fuel be, with cost, reliable operation, and ease of use being the criteria.


mac49 11-13-2003 01:29 PM

RE: gas fuel with glo plug no ignition
In searching the web I've found that there have been several other discussions concerning the mixing of fuels at other websites. None that I recall that were for the purpose of using a glow plug to ignite a methanol/gas mix in a two cycle engine conversion though. One site said that he was able to mix up to 30% gas with his methanol before it started coming out of solution. He also recommended WalMart's brand over Colman's for white gas. It was better filtered. Another site talked about using up to 3% acetone to help keep the methanol fresh, since it would absorb any moisture before the methanol did. This might make a pretty interesting mix to try with either a 40:1 or 50:1 oil mix depending upon the engine. I've got a number of engines in various states of being sacraficed but my spouse has other designs on my time instead of my playing with my toys. I'm interested in following up but won't happen until I get her house finished, next year.

wvarn1957 11-13-2003 02:05 PM

RE: gas fuel with glo plug no ignition
Av8tor, you raise a very valid point about the lead in AvGas. The 100LLAvGas was actually a compromise between the aviation industry FAA and EPA. All of the older engines required some lead in the fuel to prevent valve failure. I don't remember all of the details, but the Continental engines would experience valve failure with as little as 200 hours operation on no lead gas. The Lycomings were not as bad, but still experienced premature valve failures. It all had to do with the metallurgy of the valves and seats. Consequently the lo lead 100 octane was approved. Plug fouling due to the lead was never the problem. The Lycoming IO 540 in my Cherokee never needed plugs before the 2000 hour engine overhauls. The lead would be a poison to the platinum on the glow element over time.

I have an OS 60FP that I modified the carb to be able to run on gasoline with spark ignition. Using a 13 X 6 MA (black) it would turn 11,700 on glow and 11,300 on gas with spark at 30 deg BTDC. Over the weekend I'll pull it out of the box and try some runs with different fuel mixes.
This won't be completely applicable because I'll have to use 18% oil. It might point in a particular direction.

Intuitively though, I believe that the best performance would be a mix of gasoline, methanol or ethanol and acetone. Probably around 15% methanol or ethanol and 5% acetone. I'm not sure about the Coleman fuel, since it is blended at a much lower vapor pressure because of safety concerns. However in a blend with the alcohol and acetone it might not make any difference. Hard to say.

As far as costs are concerned, gasoline is about $1.40 a gal. Methanol can be obtained for about $2.50 a gallon. Denatured ethanol is about $5.00 a gallon and Acetone about $7.50 a gallon. This would equate to about $2.00/gal using methanol and about $2.30/gal using ethanol.

I'll try a few runs with the 60 and post the results.

aero nut 11-13-2003 03:52 PM

RE: gas fuel with glo plug no ignition
Those combinations sound logical, I already have that weedeater mounted on a test stand I will try the 15% methanol, 5% acetone and 50:1 gas/oil mix ratio with 92 octane fuel mix (doesn't the 92 octane already contains 10% ethanol?).
I think that on the last issue of Model Airplanes News at very end there was an article about a transatlantic flight with camper stove gas as the fuel used for the entire journey, they manifested that the camper fuel is more power efficient and it is requiered less of it to do the job of methanol.
What do you guys think of this; I am gong to try replacing camper gas for methanol also and I will set a table for the diferent mixtures indicating the results for rpms and the props used.
I will keep you posted on the results.

av8tor1977 11-13-2003 08:21 PM

RE: gas fuel with glo plug no ignition

wvarn1957-RCU, you are absolutely right about the valve problems. This also occurred in the automotive industry with the switch to unleaded fuels, until they came out with hardened exhaust seats and better valve materials. The lead lubricates the valve seat, and is much nicer to valves in general than unleaded fuel.

However, in the aviation engines, I have seen a lot of plug fouling problems on the older 80/87 engines when using 100LL. We often use a special vibrating tool to break up the little lead balls that foul the plugs. It usually occurs on the bottom plugs interestingly enough. As we've said, this lead could be a real problem in our model engines.

Another good point, is that many of the auto fuels available today have up to 10% alcohol already in them. We have a lot of problems with this in ultralight airplanes, as these aircraft also use two-stroke engines almost exclusively. The problem is that the alcohol, being hygroscopic, will absorb moisture right out of the air. Normally this is not problematic, but with a two stroke what happens is that the water that the alcohol absorbs will not mix with the oil in the mix. There have been a lot of ultralight airplane engine failures do to this, and we explicity warn people NOT to use gasoline with alcohol in it in their ultralight airplanes.

In light of this, I would recommend that anyone using a gasoline/alcohol mix in their model engines to mix their fuel only small batches, keep it tightly sealed to prevent water absorption, and try to determine if the fuel already has alcohol in it before adding more.

As always, other input/opinions are welcome,

wvarn1957 11-15-2003 11:03 AM

RE: gas fuel with glo plug no ignition
I made several runs on the 60 FP today, but I couldn't find my gas modified carb so used a smaller throat perry. Basic conditions were: OS F plug, 20% Klotz oil, 13 X 6 Zinger prop. On each run I varied the amperage on the plug to see if it affected the timing. I saw little or no difference at full throttle, but it did make a difference when it was below 3000 rpm. Listed below are the numbers:

Omega 10% gasoline 10% Methanol 15%Methanol 20%Methanol 25%Methanol

9100 8200 8300 8400 8600 8900

Second series was with 5% acetone added to each blend

9200 8300 8400 8600 8800 9000

Only when the Methanol content was 20% or higher would the engine idle below 3000 rpm without the the glow plug heat, except on glow fuel. I ran the 20% and 25% mix with ethanol and the results were essentially the same except the needle adjustment was a little more sensitive than with Methanol.

I thought about trying some diethyl ether like the diesel engines use, but didn't have any available. Ether probably is a better ignitor than acetone would be.

One other thing. The OS has head shims installed to reduce some of the overheating problems I had running on glow fuel, so it is probably pretty close in compression ratio to an un-modified weedie.

Even though this would seem to indicate that Gasoline-Methanol mixtures can be used with Glow ignition, I think I'll stay with spark ignition. The principal reason is reliability and lower fuel mixing problems. Since I have several CH units which can be switched from plane to plane I have already made the necessary investment. One other point, I'm not sure about Glow plug life. The F plug was new out of the package to start. After the runs, It still glowed brightly, but definitely had the beginnings of carbon buildup. Probably as the result of cracking some of the -ene compounds in the gasoline.

Sorry about the table apperance, but my formatting efforts couldn't get the numbers to line up.

One thing I forgot to mention is that the engine had a distintly softer exhaust sound when running on the gasoline mixtures than on straight glow fuel. It also produced a much smokier exhaust, eaven at the leanest settings. This is probably due to a slower flame front with gasoline than Methanol.

antslake 11-16-2003 07:50 AM

RE: gas fuel with glo plug no ignition
Is there a way to get water out of menthanol once it is absorbed into it?
Some kind of water separator?
I have 20 gallons of it that I use in my tartan twin, and want to make sure I don't have water in it when I go to mix it up.

av8tor1977 11-16-2003 09:36 AM

RE: gas fuel with glo plug no ignition
wvarn1957-RCU, Thanks for all the great info and research. It sounds like the 25% methanol, 5% acetone, gas mix is the key then. I think I will modify a weedie for as much compression as I can get, and give this a try when I have the time. Having an on board glow igniter would defeat the whole purpose of the exercise, so the key is if we can get a reliable idle on just the glow plug. Where do you get methanol and ether? Thanks again for all the effort.

Antslake, I don't know of any way to get the water out once the alcohol has absorbed it. Years ago my father used a product called "Dry Gas" to treat gasoline that had gotten water in it, but I suspect it was nothing more than alcohol itself, which would then absorb the water that was in the gas.

Take care,

av8tor1977 11-16-2003 09:41 AM

RE: gas fuel with glo plug no ignition
Another thought is that the weedie engines with the much lower oil content in the mix would probably idle better than the results you saw. I'm thinking Amsoil at 100:1.



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