I am considering getting a gas engine- either Fuji or Zenoah. I wanted to know, what is the difference between a glow engine and a gas engine (other than the fuel of course). For an example, lets take

Glow: 120AX or 140RX
Gas:ZENOAH G26 Air Engine
Fuji Imvac BT-24EI 24cc 1.5ci Gas
Fuji Imvac BT-24A 23.9cc Gas

I have exclusively flown glow so far. So, what is the fuel additive to gas? You know, like we add castor or synthetic lube to glow fuel... Sorry if I am a bit rough around the edges but I have no idea regarding gas engines and what fuels and additives they use, so I need a "technology primer"

Ameyam

Gas engines are super simple.. pump gas like what would be put in your car, and some 2 cycle engine oil mixed in the right ratio (i.e. 32:1), the same kind of stuff that you put in a weed wacker or chain saw.. my old man runs his with Stihl ultra or something like that.. good stuff and synthetic i think.. some guys swear by synthetic, others say it doesnt matter.. Iam of no opinion either way.. but can afford the synthetic oils..

Ameyam,

RCU has a forum dedicated to gas engines, where a universe of information can be found:

http://www.rcuniverse.com/forum/forumid_142/tt.htm

Some of those good threads, that I have liked, may help answering your many questions:

http://www.rcuniverse.com/forum/m_8673009/tm.htm

http://www.rcuniverse.com/forum/m_9847845/tm.htm

http://www.rcuniverse.com/forum/m_9944773/tm.htm

http://www.rcuniverse.com/forum/m_9891568/tm.htm

http://www.rcuniverse.com/forum/m_9891568/tm.htm

My rule of thumb is: I'll go up to a 75 2-stroke and a 125 4-stroke. Anything above that is gas

.91 two stroke and 1.20 four stroke then gas. I just really like the SK .91s. As to the make of the gas engine it would pay anyone wanting to go gas to look in the gas engine forum and see what is going on. New gas engines are coming out very fast and hard to keep up with. Other then my Zinoahs I don't think any of mine are still made?? RCS and Brison, even a Fox twin.

I'm glad this topic came up. I am considering moving up to large scale and gas, but would prefer not to use gasoline for two reasons. One I live in a small apartment and storing gasoline may not be an option if the manager knew. [X(]

Back in the 60s & 70s I raced mini bikes and mini cycles in Southern California and it was common practice to convert our bikes to Methanol and maybe a tad of nitro. The basic rule of thumb was to triple the jet size and cut the oil in half for two strokes.

I would be very interested to hear from those who have done this with the current RC engines.

The type of ignition doesn't matter. It's the fuel that makes the difference. Methanol will give around a 20% power boost over gasoline, as I recall. But you do burn a lot more methanol than gas for the same flight time.

Write a book Ed!!!!!!!!!!!!!!!!!!!!
Gene

I don't really see the difference between storing a gallon of gasoline conpared to a couple gallons of methanol based fuel other then the smell. Both are pretty much just as flamable. As for using one or the other in a large model engine there are many advantages to gasoline. First would be the expense of gas. For a gallon of gas with penzoil 2 stroke oil added I pay about 4.50 here in sunny CA. For methanol I would have to estimate it being closer to 15.00 not to mention the gas used to drive to the speed shop to get it. Being a special trip one my be prone to buying and storing more then one gallon at a time. On a 50cc airplane run on gas I carry a 20oz tank, good for 20 mins of flight. The same engine on glow would need a 40 oz tank and not get the same 20 mins. Alcohol also attracts moisture as it evaporates. This causes glow engines to rust internally ( Bearings, crankshaft). Gasoline engines run cleaner. IMO they are also safer to operate as the ignition tends to make them behave a bit better. If you don't agree, how many of you would hand start a 150cc glow engine?


As for the original poster, my vote obviously goes for gas but do yourself a favor and look at more engines that are available. The brands that you mention are some of the lowest power to weight ratio engines available. They also have magneto ignition which means they have fixed timing. That means difficult starting and less power. The new DL20 will out power your list and be much lighter.

My LHS has a 120AX (ringed) engine. All his other engines have been sold but this specific one didnt sell because it did not have the original muffler. Hence the box is starting to get into a bad shape. They suggested I take the engine "on approval basis" and show it to my mentor, then purchase if everything is OK. Since I was contemplating a H9 Funtana above, this is the ideal engine. I will post pictures of it later today. Its a brand new engine and unused, bu the baffle seems to be of a different color from the rest of the engine. It was starting to lose lube due to just sitting, so I put a few drops of light machine oil in for now

Ameyam

I have a 120AX, which started life on an ESM FW190, and flew it quite respectably. I put a second one together and this time used an MLD28 gas engine, which also flew the plane well (better in fact, however the second one was lighter due to a built up wing).

The 120AX has now replaced a Magnum 120FS in a 65" Midwest Stearman, first time out Sunday seemed that it gave me the extra grunt I was looking for.

Without getting into the gas vs glow debate, my experience with the 120AX is good, so if you can get a fgood deal go for it!

Terry

Smell. I have my gas can in my shop. I have one of the caps with a fuel line that plugs into the pick up tube, there is no gas smell in my shop unless I have just flown one of my gas planes. The plane/engine is the gas smell problem, not the can of gas. The same thing can be said for my glow planes. Even more my clothing after a day at the field flying glow planes. Some people run Coleman Fuel/white gas in there gas engines and then there is no smell at all. The gas smell only lasts a day or so anyway. Just a choice thing, I like them both.

So what do you think. Note that the baffle in the carb is of distinctly a different color than the rest of the engine. But the engine has obviously never been used. The glow hole is brown as I had just put in some machine oil like I mentioned in my earlier post


(By the way, sorry for having to hold it with my feet while photographing. Dont have more than two hand you know)

Ameyam

I'd argue that glow engines are simpler and once tuned easier to maintain.

Glow engines do not require ignition systems, pumps, diaphrams, float bowls, etc. some of which wear out or degrade even if the engine is not in use...

That said, gas engines can be very economical.

By weight, glow engines produce more power, so you have to load a plane down more to get an equivalent amount of power output, which negatively affects performance.

The upside is gas is CHEAP compared to glow fuel, and gas engines run reliably once tuned.

Glow fuel stores VERY well for very long periods of time, provided it is kept in a cool preferably dark place. The key is to keep the container sealed until you are ready to use it, and once opened finish with that container within a reasonable amount of time. I've run glow engines on fuels which are over six years old without a single problem.... I've also have had glow engines out of service for 3-4 years ( with afterun oiled applied initially and enclosed in a baggie around the cowl... ) that start up without a hitch.... usually if a gas engine is sitting around this long, I'd have to rebuild the carb... though the latter is not difficult given a repair/rebuild kit.

For me what dictates the engine is the size of the plane.

Normally for planes in the .90 size range and below I go glow or electric.

Planes above 1.40 in size it's usually gas, as long as there is not an overriding reason not to...

In between it's a toss up.

I don't see anything wrong.

If anything the engine is like new. It seems to have been run, but only briefly.

I believe this would have to be a first......man modeling an engine with feet. At least you could of got a pretty woman to take your place!

Opjose,

two questions:

1) The engine hasnt been run. See the side of the piston has no marks on it. In that case, is the difference in color between the engine and baffle normal?

2) Is it suitable for the Funtana 125?

Ameyam

PS: flygilmore, the engine wouldnt stand up on its own and I didnt want to get oil into the bed mattress[8D]

Iguess growing up tinkering with chainsaws, weedwackers, and small motorcycles has given me a bit of a different opinion of easy.. its true.. its a toss up..

I assumed it had been run because of the piston ring color, but you may be right...

The color of the throttle body is without consequence. The finish may have absorbed coloring from afterun or whatever was left in the engine for storage.

As long as it moves smoothly there should be no problems.


Oh, yes!

The Funtana 125 is spec'd for a 1.25 FOUR stroke engine, and you are looking at installing a 1.25 TWO stroke engine.

Power wise that would be like putting in a 1.60 or so FOUR stroke engine, so you'll have PLENTY of power.

I'd stick to a wider low pitch prop...

I fly my Funtana S90 ( same size and just a bit less weight than the 125 ) with a Saito 1.00 using a 16x4W prop.

The same type of prop ( or similiar) would let the AX unload more for higher RPM's but let it pull like a hyped up mule.

You can also side mount that engine in the Funtana with a Pitts style muffler if you choose...

That settles it. Will be most likely purchasing this engine. Will be ordering both a standard and pitts muffler (Slimline). Will try the standard muffler first, I have observed it gives more power and relaibility.

There was nothing used for storage. The engine was left in the original box (they are into the business of selling at the LHS, not into knowing what they sell). When I got the engine both the carb and piston felt a bit rough, but nothing of major concern otherwise I wouldnt even have picked it up. A few drops of light machine oil and everything felt smooth again. This is my first ringed engine (so far I used only ABL) so I guess the thing will feel different initially. I will have my mentor look at it tomorrow and then take a final decision.

In any case, I will break it in with plain castor without any nitro for maximum protection initially so that I dont damage anything during the break-in. Then I will transition to the Klotz based fuel we are using with 80-20 synthetic-castor blend in the lube which will definately make it run cleaner and have 5-10% nitro in it then. Any suggestions?

Ameyam

I'd run some nitro in it initially.

Lack of nitro will make the engine more difficult to tune.

You should break it in first with Nitro then start backing off only after you have it running reliably.

I've never run an engine with NO nitro, but I do tend to run most of my larger glow engines with only 5% now-a-days.

The tuning "window" is just a bit tighter, but the engines run well... and the cost savings is substantial.

The barrel in the carb is a different color because it is a different metal. It is likely a mild steel, where the rest of the carb is aluminum.

Anything bigger than a 1.20 and I'd go gas.

Yup what I suspected, but I wasn't sure.

I do it all the time. In particular, some of the SuperTigers are quite happy with no nitro and their instructions specifically mention that. I've had very good success with the diminutive G.34 which produces amazing levels of power on 80/20 FAI fuel. I clocked an old C/L Sterling Ringmaster at 93mph with the G.34 on 80/20 FAI fuel and that was spinning a fairly fat Taipan 9x6

Out of curiosity, how does the lack of nitro affect the engines from your perspective?