Teach me about RC fuel?

I've flown RC for a long time & as you know, building a similar 5-cylinder glow radial. For sure I plan on buying RC fuel for the radial because there are no advantages I can think of mixing your own, but some potential disadvantages. I would recommend selecting a reputable brand from your hobby shop at least for the first quart or gallon & ease into it, so you have eliminated an variation there's. For example Powermaster or Morgan fuels (I might be dating myself). They offer gradations of oil & nitro content. But there are other goodies in there that you would be guessing at - stabilizers, anti-foam, ingredients that help castor & synthetic get along. The only difference to the Edwards from what commercial RC 4-stroke fuel would be is you are potentially introducing a tiny bit of lubrication oil into the mix via the Edwards lubrication system. But whether that translates into a net increase of oil% in what becomes your combustion mix is debatable IMO. But you do want compatibility so that the lubrication oil doesn't go funky. That's likely why Edwards recommended castor, but fuels have evolved since then too. Slightly higher oil content wont really hurt anything (within limits). Lean oil content is the bigger worry, heat & seizure is usually not far behind.


Methanol is sold by grades of purity & engine running is sensitive to it, so you need to be sure what you are getting in the custom blend world. Even otherwise good commercial fuel can go bad over time in partial/opened containers in humid conditions. Increased nitromethane content as a general rule may help your starting, idle & transition. But there many other variables involved (glow plug heat type, compression, break in condition etc.). Some castor oil content within an otherwise synthetic oil based fuel is very common in commercial fuels, even among the best fuels for demanding applications. Pure castor (only) has fallen out of favor for reasons mentioned. Its a bit messy & can varnish more-so than synthetic. Some of the fuel blenders sell their (premix) oil separately so you could go that way with the circulating lubrication system IMO.

What is probably THE most important thing for glow engines is maintenance ritual. If the engine is going to be parked for a couple of months, best to remove the plugs & partial disassemble to the extent you can flood the internals liberally with a good quality oil so that the important surfaces are all coated. I just store engines this way in a ziplock bag. When it comes time to run, drain this oil out, flush with a bit of fuel & ready to go again. RC after run oil is sold for this purpose but like most things, opinions vary. Some blend their own. Some from the high performance community advocate pneumatic tool oil for this purpose. I've used both successfully. The key thing is it coats & protects from corrosion in the down time & must flush away with no real residue or compatibility issues. I'm leary of people who use gear oil or ATF oil because some of those blends don't play well with brass & bronze (of which we have several parts in the radial). Other considerations like silicon O-rings, seals, synthetic gaskets are sensitive to certain ingredients. I steer away from WD-40 for this & other reasons.


Hope this helps!
 
20-30% nitro for 2 strokes not 4 strokes.

I don't think that's a hard & fast rule. Really depends on the engine & application. This excerpt is from OS Sirius 5-cylinder radial instructions, a pretty similar engine to the Edwards with the exception of Edwards separate lubrication system. OS say's pretty much the same in their other multi-cylinder engine manuals.
 

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I have not run glow or gas in quite some time now (I am all electric) but would lean towards absolutely no more than 20% nitro. 10% would seem to be better because you are not necessarily looking for a lot of power, but rather, a nice running engine with some longevity to it. I too would add a tad of castor just for memories sake, but if you have no prior pleasant experiences when burning castor oil then it doesn't matter ;)
 
20-30% nitro for 2 strokes not 4 strokes.
My Saito 4 stroke recommends 30% heli fuel. It has been drinking this for the last 10 years and still going strong.
The best fuel depends on many variables. Only testing can find the best for a given combination of variables.
 
I have not run glow or gas in quite some time now (I am all electric) but would lean towards absolutely no more than 20% nitro. 10% would seem to be better because you are not necessarily looking for a lot of power, but rather, a nice running engine with some longevity to it. I too would add a tad of castor just for memories sake, but if you have no prior pleasant experiences when burning castor oil then it doesn't matter ;)


Love the smell, love it.
 
I don't think that's a hard & fast rule. Really depends on the engine & application. This excerpt is from OS Sirius 5-cylinder radial instructions, a pretty similar engine to the Edwards with the exception of Edwards separate lubrication system. OS say's pretty much the same in their other multi-cylinder engine manuals.


I guess I've been away from nitro too long. I'm essentially all gas these days. Edge 540/DA120, YAK/3W-106, Sukhoi/DA170 but I have dozens and dozens of nitro engines, all 2 stroke.
 
It really depends on the type of RC (glow) engine. Sport engines target a balance of cost & reliability. Something like 10-15% nitro is typical sport fuel. Just to highlight an interesting contrast, on another end of spectrum some of the highest HP/displacement engines are 2-stroke pylon racing engines. The F3D/FAI rules prescribe 0% nitro (80% methanol + 20% oil). The rules have been this way for decades now. In fact I think for the longest time it had to be castor oil, maybe since changed. These engines make stupid amounts of power but kind of like an F1 car, purposed designed. Idling & transition is not in the mission statement LOL. Before electrics dominated pattern/aerobatic events, it was common to run 20-30% nitro in 4S engines as the rules didn't stipulate fuel & it just worked better.

Sadly my local hobby shop looks nothing like it did a few decades ago. The shelves used to be lined with engines & gallons of fuel. Not so much these days. I'm all for modern technology & fly electrics too, but starting to feel a little melancholy about a bygone era. But, like the OP, I found a lot gratification machining & scratch building a radial engine. If push comes to shove I will mix my own brew! LOL

Another thing I will pass on is 4-sroke plugs are getting harder to come buy, at least in my neck of the glacier. I found this place that sells OS plugs (and many other Japan engine goodies). The were expedient shippers & great to deal with.
 
It really depends on the type of RC (glow) engine. Sport engines target a balance of cost & reliability. Something like 10-15% nitro is typical sport fuel. Just to highlight an interesting contrast, on another end of spectrum some of the highest HP/displacement engines are 2-stroke pylon racing engines. The F3D/FAI rules prescribe 0% nitro (80% methanol + 20% oil). The rules have been this way for decades now. In fact I think for the longest time it had to be castor oil, maybe since changed. These engines make stupid amounts of power but kind of like an F1 car, purposed designed. Idling & transition is not in the mission statement LOL. Before electrics dominated pattern/aerobatic events, it was common to run 20-30% nitro in 4S engines as the rules didn't stipulate fuel & it just worked better.

Sadly my local hobby shop looks nothing like it did a few decades ago. The shelves used to be lined with engines & gallons of fuel. Not so much these days. I'm all for modern technology & fly electrics too, but starting to feel a little melancholy about a bygone era. But, like the OP, I found a lot gratification machining & scratch building a radial engine. If push comes to shove I will mix my own brew! LOL

Another thing I will pass on is 4-sroke plugs are getting harder to come buy, at least in my neck of the glacier. I found this place that sells OS plugs (and many other Japan engine goodies). The were expedient shippers & great to deal with.


Jett, Nelson........ engines that turn upwards off 30,000rpm..
 
My favorite 2 stroke would be the YS 60 short stroke or the Jett .56. Astounding power.
 
The smell of castor oil fuel always brings me good memories. But I would avoid using much of it because of the burnt oil mess it can make.

One idea is find your local R/C flying field and start hanging out there. Talk to the guys there and ask them questions about fuel.

Then when you know who is who at the field maybe you can find someone to put your engine on a plane and fly it!

Maybe if the interest grows learn to fly yourself.

The season is almost here!
 
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