2W0EPI

As a kid, like many here, I had a Cox pt19 trainer cl, I remember vaguely that I once used straight methanol/castor hence zero nitro and it worked but the drop in power was somewhat noticeable however it powered enough to be useable. Given straight methanol and advances in glo engine technology, what do you think?

Straight methanol/caster is somewhat cheaper than nitro mixes. Also, nitro contributes towards higher engine wear/corrosion.

TheEdge

My Feedback: (788)

The best person I know of that can provide a very accurate answer to your question is Brutus. In all my years, i can honestly say that I don't think I have encountered someone as experienced and talented as him in the hobby with respect to engines.. Sure, he doesn't deal with BS very well but if one can put that to one side (BS), then a lot can be leant from him.

the Wasp

My Feedback: (1)

I would think that depends on what the user wants from his plane. I guess I am saying that all fuels have their place in this hobby.

Jim

1QwkSport2.5r

I have mixed my own fuel for nearly a decade. I use FAI fuel (true FAI fuel is 80% methanol 20% castor) quite a bit myself. It’s dead cheap to make (about $6-8/gallon) and works quite well especially if you have engines designed for low nitro fuels. If you have an engine that needs a little kick, 2-3% acetone helps with starting and idle quality. Otherwise the biggest differences you’ll notice is better fuel economy, the exhaust note will soften (it won’t have the nitro ‘bark’), and the exhaust won’t completely burn your eyes like napalm. . The engines designed for nitro will likely need a head shim removed to take better advantage of the fuel. To get the absolute most from FAI fuel, you would need to machine the engine parts to get the compression ratio up to as high as 13:1.

Use a HOT glow plug. Enya 3 is perfect.

Jesse Open

^^^^^^^Yes^^^^^^^

2W0EPI

What exactly do you mean?, the reason for my thread is to reduce fuel costs, the question is, can I ditch 5% nitromethane because here in the UK only methanol and castor oils are available to buy. You need a special license to handle nitro, the question again is, will 5% nitro void fuel still be of use or viable?

1967brutus

If your queste is to reduce fuel costs: Electronic solutions to modifying glow engines of all sizes to gasoline
I reduced my yearly fuel bill from €500,- to €50,-
The cost of a conversion is between €100,- and €170,- approximately and depending on how much effort you put in it.
I can convert 3 engines per year and still break even, and I have done that for several years, I now have a fleet of 12 engines like that.

Jesse Open

What exactly did you want to know?
The nitromethane is an option taken for any of several reasons but , in most cases yes you can easily do without it. Some of the smaller engines are a bit less tolerant.
You can also convert to using Methanol/Oil fuel with CDI sparked ignition. You will burn even less fuel, make as much power or more than you did with 10% nitromethane.



Your original post was rather vague and at least two reeponses were suggesting that an accurate response would require a bit more info.

2W0EPI

Whether a 2 stroke 5% nitro engine would run okay without the 5% nitro? without to much degradation in performance.




Thank you. I will in future buy only methanol/castor and make my own low cost fuel.The cost in fuel is very important in rc flying because gas engines are 2x and 4x the price of glo engines and there are many threads here on converting glo to gas at great risk and expense towards gas for one reason only and that is cost of fuel. Nitro fuel is expensive.

1QwkSport2.5r

Engines that run fine on 5% nitro will very likely run fine without any nitromethane. Needle settings might be a little touchier, but not much different than with 5% nitro.

the Wasp

My Feedback: (1)

to add. the lower your Nitro rate is, the higher you can rase your compression.

Jim

2W0EPI

I notice fuels containing pure castor oil are more expensive than synthetic oils, is there a difference here?, will using synthetic oil reduce the overall engine life?

1967brutus

Normally not, as long as you use good qualities. I do not know which oils are availlable at your location.

1QwkSport2.5r

European synthetics are said to be much better; perhaps from closed end PAG or a PAO ester. Synthetic oils miscible in methanol here in the states is garbage. I mix my fuel for anywhere from $4/USGal to $20/USGal depending on the blend. FAI fuel is $4-5 a gallon using all virgin castor oil. Castor is about half the cost of even the cheapest synthetics here. It might be different there, but you’re about 3500 miles closer to where the castor plants are grown than I am. One would think castor based fuel would be cheaper. Unless the shop selling it is raking you.

2W0EPI

I can get 4x 5litres of pure methanol for around £37 (Ebay-free post) and I can buy castor 1 litre for £9 from amazon.

I can buy 80/20% ready mix 5 litres for £22 20% synthetic or £25 20% castor.

I can buy 5 litres 5% nitro with synthetic for £26

If correct that synthetic oil is fine then there isn't much in it.

mgnostic

This is another question where the answer is "it depends". Newer engines with ABC pistons and liners do pretty well with synthetics. Cox engines and older engines with ringed pistons or lapped cast iron pistons still need at least a little castor in the blend.

jaka54

Hi!
You can use 80/20 fuel in most two strokes and you will not notice that much difference than with 5% nitro fuels.
But four strokes are a little more demanding (sensitive on needle settings).
I personally run all my four strokes on 5% nitro, 15-20% Motul micro syntetic oil and rest methanol, mix my own fuel since I started flying 48 years ago. but then used 20% Castor oil. The smaller two strokes does not like fuel not contaning castor oil like COX Baby Bee , Tee-Dee and some small 1.5-4,5cc two srokes (MVVS) so in these I use either a blend of syntetic oil and Castor oil or just castor, but still opt for 20% oil.
For the small COX engines I use 15-25% nitro and 20% oil. Here in Sweden Nitro is not that hard to find.
You do not have to worry about engine wear when using nitro based fuel, on the contrary, nitro (5-10%) makes needle setting much more easy and thus makes the engine thrive and run cooler than with just 80/20 fuel.

1967brutus

It is not the engine temperature that causes issues, but the tendency to pre-ignite due to running lean. Nitro FORCES one to set a richer mixture for a given compression ratio.
Glow ignition engines need about 20% excess fuel or the ignition timing destabilizes and THAT causes the thermal runaway. Control timing (for example spark), and you can run the same engine at stoichiometric fuel/air ratios, way hotter than the same engine would run on glowfuel. For most engines, 150 deg C is not a problem mechanically or thermally. It is the preignition that kills them. Counterintuitive, you then need to raise CR, in order to force a richer mixture, if using a glow engine on low or zero Nitro.

Jesse Open

The "way hotter".... on spark ignition / methanol fueled engines is often due in large part to ignition timing settings. Trying to run the same timing on methanol as is typically used for gasoline is begging for heating problems.Retarded timing can cause temperatures to rise sharply. Heating exhaust valve as well as vaporizing oil from cylinder walls.
This in turn can be aggravated by lean mixtures.

Using the correct timing promotes cooler running, better power output and lowers fuel consumption.

2W0EPI

I do not understand what you have written here... a spark ignition methanol engine, as far as I am aware, the glo engine does not have an auto advance controlled ignition like a petrol/gas engine and although I'm unsure, the glow engines ignition occurs when the temperature, of the glo plug element, and pressures are just right for ignition of methanol fuel. I would also like to point out that glo engines were conceived in 1948, quite late after diesel/petrol engines were conceived.
I believe that some sort of catalyst occurs in glo engines by way of what the glo element wire is made of namely platinum which is a very noble element metal.

My question is, how do you control ignition timing of a glo/diesel engine as you cannot tell the engine when to spark like you can with petrol/gas?

1200SportsterRider

You control the timing on a Diesel by raising or lowering the compression, a greater load requires a lower compression setting. You control the timing on a glow engine by enrichening or leaning the mixture. A leaner mixture increases the combustion temperature and therefore advances the timing.

An early Saito 150-s with 11.24 to 1 compression ratio running at 6,000 rpm, with the timing set at 31 degrees btdc, at 33 btdc it knocks scarily. It turns the Xoar 16 x 8 at 9,150. The fuel is 10% Wildcat with 18% full syn.

OS LA .65happily turning a Bolly Clubman 13.5 x 8 at 9,300 rpm on DDD abc mix.

2W0EPI

It might be worthwhile mentioning that spark/petrol/gas ignition can also be made to run rich/lean but ignition timing is done via the cdi, I've also been doing some reading on glow engine ignition timing which is hardwired via the inlet port slits in the sleeve lining, which tells me the glow ignition timing is predetermined via the engines sleeve. inlet porting's..

Jesse Open

Yes, a spark ignition methanol fueled engine. Glow firing manipulation is pretty limited.
You can precisely control the ignition timing by converting to CDI, spark ignition.
CDI applications apply to methanol fueled engines very nicely. CDI minimizes any reliance on nitromethane. It improves the power, idle and response over that of glow, Also decreases fuel consumption overall.

Want better control over the firing point, spark is a good option.

Side note:
Yes, commercial viabilty of glow ignition came along in the later forties. Are you aware that many fliers were already running methanol on spark ignition? Some even discovered they could file the side electrodes of their spark plugs thin and keep the engine running after turning the spark off? Start on spark, run long enough to get the thinned wire electrode glowing, shut off the spark system and the engine kept right on running.

1967brutus

That is because that info is incorrect, makes suggestions that are untrue, and in general makes no sense at all.
The first statement is
is literally plucked out of thin air, somehow assuming everybody does it wrong or something?
-A properly set up spark ignited, methanol burning engine WILL run hotter than the same engine on the same fuel using glow ignition. There are no ifs and buts about that, and the proper timing required for Methanol is widely known. It is stated in every installation manual commercially availlable for model engines. Gross negligence excluded, it can be assumed that ignitions are set as per instructions, and then they are what they are...

The second statement is: is provable untrue.
-The only way to make a spark ignited methanol burning engine to run as cool as the equivalent glow engine, is to recreate the combustion conditions that occur in a glow engine: when you use the exact same fuel/air ratio as the glow engine would, and then advance the timing to gain back the lost RPM.
But... then you would have an incorrect timing, AND have the same fuel consumption as a glow engine, which means that "properly timed engines run cooler and show better fuel economy" is untrue by definition. They either are improperly timed and then consume excessive in order to run cooler, OR they are properly timed to run more economical but then they run hotter.

Having said that: "Cooler running" is NOT rocksolid connected to "better running", NOR with engine longevity. There is this word in any language, equivalent to "too"...
"TOO hot" affects longevity, and so does "TOO cool", but "hotter" and "cooler" in themselves are fairly meaningless and mostly used in ads for lubricants as IF that is somehow meaningful or a good thing. It isn't. Not in this context. There is a reason why engine manufacturers (cars, bikes) equip their liquid cooled engines with specified thermostats. Air cooled engines always are a compromise WRT running temperature, and constructed such that they can handle a fairly wide range.
Check any tuning kit (official or aftermarket) or upgrade kit, or OEM offered option. You will never find a different thermostat in any of those kits, "for cooler running". Maybe a larger radiator if horsepower is increased by a large amount, but never a thermostat. "heat" is not the same as "temperature".

2W0EPI

Never heard of anybody converting a glo to spark ignition, to run it on methanol, before?. I personally don't see any benefits here which might be why you never hear of them.

Now, on the other hand, converting glo to petrol/gas I can see major advantages here. If you are going to convert a glo to cdi then do it for gas/petrol.