Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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..

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

.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.

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

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:D:D:D)

Ameyam

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

I don't see anything wrong.

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

RE: Difference between Gas and Glow engines performance wise
 

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!:D

RE: Difference between Gas and Glow engines performance wise
 

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]

RE: Difference between Gas and Glow engines performance wise
 

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..

RE: Difference between Gas and Glow engines performance wise
 

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...

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

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.

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

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

RE: Difference between Gas and Glow engines performance wise
 

the bottom line is Gas is better for several reasons .... the cost of fuel is way cheaper, the reliability "engine stalls" is way superior to glow, they don't require tuning before every flight, very low maintenance, fuel tank location not critical like glow, NO MESS !!and on and on. i just got into electrics as i fly turbines and gas stuff and I'm getting rid of all my glow stuff "i don't really use it much anymore" . i won't buy a plane that i can't use at least a g-23-26. Zenoah are old school engines or maybe they were just ahead of their time. they are a very good engine. I have heard a lot of guys saying their ignition modules on the fuji's burned out along with crankcase problems . I recommend DA , Zenoah , ZDZ or 3W . in my opinion they are the best. remember when it comes to cost, you pay for nothing , you get nothing. Once you go gas , you won't go back . WB_1

RE: Difference between Gas and Glow engines performance wise
 

The flash point of gasoline is much lower at atmospheric pressure compared to methanol and even nitro. It takes compression well above atmospheric conditions for methanol to have an advantage over gasoline and methanol runs cooler than gasoline. Also, the evaporation of methanol does not attract moisture. Methanol being subjected to moisture does.

RE: Difference between Gas and Glow engines performance wise
 

I was going to move to a larger plane than I have been flying so far and was considering a Seagull Mew Gull powered by an OS 120. However after talking to some people at our local club I was considering a DLE 30 gas engine. Does anybody here know for sure if the DLE 30 will fit in the Mew Gull because it looks much bigger particularly in length with the carb sticking out the rear? Or is there a better choice of gas engine than the DLE 30?

RE: Difference between Gas and Glow engines performance wise
 

The only reason I didnt want to use nitro is that, since it is an oxidiser, I fear for rusted bearings if any is left behind in the engine.

Plain castor only to protect the engine as much as possible during its initial run-in when the piston and liner ar in the mating stage.

The baffle has be baffled however, it feels rough to turn even after putting in the oil. Atleast it feels rougher than my other engines but nothing a standard servo cant take care of. With my luck with engines this year, I am worried about everything

Ameyam

RE: Difference between Gas and Glow engines performance wise
 

Did you purchase the engine?

I have a 1.20 ax that has been run for 2-3 gallons...
They are very easy to disasemble...

At the very least, pull the head bolts and take the botton (cyl cap and look inside...
If you go further than that, take pictures...
That way you will be able to hav reference as to how it goes back together...
when you pull the cyl button, make sure the inner sleeve\cannula doesn't come with it...
Unless you want to take the back of the engine off and remove the piston...

Once you have done one, you have done them all (2-stroke glow)...that is...

I wish OS would convert the 1.20 AX to gas....

RE: Difference between Gas and Glow engines performance wise
 

Some engines aren't happy with it (ex Fox Stunt .35) due to a very low compression ratio. Any engines with a high enough compression ratio seem to tolerate it OK. It sometimes requires switching to a hotter heat range plug; the Enya #3 or Fireball "hot" seem pretty good with 0-nitro.

Top end power will of course be off some compared to running nitro, but unless a plane is marginally powered to begin with this is not usually a concern for ordinary flying.

Needle valve setting will change a bit. My experience has been that you tend to turn them in a tad compared to nitro mixes. The power/rpm will drop very quickly and noticeably if you've gone too far and it becomes too lean. i.e. the "sag" comes on much faster than with a nitro fuel.

I've been experimenting with various methanol/oil mixes this year. "Standard" FAI fuel is an 80/20 mix, but I've mixed 75/25 and 72/28 for initial break-in purposes with varying proportions of Castor/Klotz. An old OS FP .35 seemed particularly docile and easy handling on a 75/25 mix with 50% of the oil package being Klotz the rest castor. Three chokes to prime, and it would start on one flip 95% of the time. That FP .35 was using the Fireball hot plug BTW.

The G.34 is still on the original factory plug and has around 3 hours on it now, all running no-nitro. It too is generally a "one flipper".

Some engines, generally foreign ones intended for FAI competitions, are specifically intended for no-nitro fuels and will exhibit predetonation tendencies when run with significant amount of nitro, although there was an earlier batch of Fox .74's that had higher compression ratios and would show predetonation with 15% nitro fuel.

The appeal to me is Klotz/Castor/Methanol are available locally in Ft Lauderdale in 5gal cans, nitro seems harder to find unless you want to buy $2000 worth at a rip.

As a general statement, it seems the larger the glow engine, the more likely it is it will function with no-nitro.

RE: Difference between Gas and Glow engines performance wise
 

Our "standard" fuel right now is Klotz-100 20% with 10% nitor. That has progressed from the 80-20 plain castor mix I used last year and had a lot of issues with on a 75AX. We usually home-brew our fuel (one of the more experienced modellers does it for us less experienced or less experimented people). I have about 1 gallon sitting in a sealed container from Feb-March when flying had stopped due to non-aero reasons

kochj, havent paid for it yet. Its on "approval basis" due to "good relations" with my LHS (Guess that means I bought a lot of stuff recently;))

Ameyam

RE: Difference between Gas and Glow engines performance wise
 

Major differences between gas and glow is in the fuel metering and the activation energy.
Glow engines are initiated by a catalytic reaction of the methanol to a hot platinum coil
Gas engines are initated by a timed spark createed by the gap in a copper electrode. What is key is the "timed" bit.

glow engines ignition timing is dependant on the heat of the platinum coil, the concentration of methanol to oxygen in the combustion chamber.
Gas engines ignition timint is dependant on the timing of the spark initiated by the ignition coil. Air fuel mixture does not affect the timing of the spark but does influence the speed of combustion.

GAsoline has a higher heating value than methanol fuel, so for every firing of the air fuel mix more heat is generated and hence more power can be released. in theory gasoline engines can be more poweful than glow engines. the reason they are often not is due to design. Most Glow engines are relatively higher compression ration engines. Methanol has a high Octane and hence it will not detonate uncontrollably. Gasoline typically has a lower octane value set by the specification for gasoline in various countries. Gasoline is rated according to the Research Octane Number or RON and this the resistance to knock at part load. the RONfor Methanol is around109RON(average).

Cmpresion ratio is the biggest determinant in the efficiency of an engine ans since Hobby glow engines are designed for max performance they do perform well thanks to the compression ratio's being higher than Gas engines.

Most gas engines sed in RC currently however have their origins in industrial equipment such as chain saws, weedwhackers, small generators etc. All these applications calls for engines operating at mostly constant speed but at high torque and they have t be durable so their specific power output per cubic inch is low. Engine designers call this under stressed. Glow engines by comparison would be close to over stressed.

So currently when we compare glow engines and gas engines we are comparing an engines that is purpose built for RC against an engines that was built with power to weight ratio NOT being a concern. And therefore gasoline engine are slated for anot having sufficient power.

That is changing however. Th new engines coming out of China have been placed on stringent diet and exercise programme and hence their power to weight ratios ar improving.

A year ago the cut off point at which gas became too heavy was around 30cc or 1.6 class airframes. Now with an engine like the DLE20, the cut off has been moved to the 90/1.20 size plane.Perhaps if the Magnum XLS 52G actually makes an appearance it will move the cut off even further down to .46 size birds. the naysayers will disagree of course.

the big change with the newer gasoline engines is the improvement in ignition timing and compression ration coupled to engine blocks that are a lot lighter.
There will always be a lower limit of mass for a gasoline engine of given capacity simply due to the fact that the hrat energy in the fuel has to be absorbed by mass and that means more metal. Methanol fuel takes more heat away form the engine on its journey to oxidation an that means that the engine can be a little lighter.


GASoline as a fuel will require different types of additives an oil. Mostly 2 stroke motorcycle oil or chain saw oils are suitable. Synthetics are highly recommended due to higher film strength and also for cooling since the synthetics designed for this market have lower heat of vapourisation and take more heat out the exhaust.


My personal preference is for gasoline engines and I ould probably stick to the DLE engines at this point in time since they do appear to be the most competeive on power (and thrust) to weight ratio

RE: Difference between Gas and Glow engines performance wise
 

So then the question would be whether to put in a 20-23cc Gas engine or 120AX in the Funtana 125. I am leaning towards the 120AX. When I showed it to the some experienced modellers, they said it was quite OK. Will show it to my mentor only on Sunday though

Ameyam

RE: Difference between Gas and Glow engines performance wise
 

Yea, I would shy away from gas in a Funtana

RE: Difference between Gas and Glow engines performance wise
 

The largest engine I have so far is a FS91SII and 75AX (depending on whether you call a 2c or 4c larger). This 120 would be quite a step seeing I skipped the 91/95 sizer.

I was really out to get a gasser but it looks like that will have to wait (again seeing that I can fly but I cant drive as yet:D:D)

Ameyam

RE: Difference between Gas and Glow engines performance wise
 

I have a saito 125 four stroke on my funtana, I had a ax120 on it at one time but found that in slow nose up flight like knife edge circuits ALL the 2 stroke engines even with a perry pump would tend to overheat and stumble on throttle up to pull out of the low slow knife edge, not a good thing! I considered putting a gas engine in the funtana but did not like the increase in weight that the gas engine, ignition and batteries would add to it. Adding weight to the nose of the funtana would take some of the fun out of the funtana in my opinion! I bought a saito 125 and have never looked back, it is light and has never stumbled on a pull out from hover or a slow knife edge. On heavier planes, 50cc and up, the reliability of a gas engine is more important because they will not float very long when the engine dies, the funtana will float much longer on a dead stick like most smaller planes will.

RE: Difference between Gas and Glow engines performance wise
 

for the funtana i would opt for the DLE20 as the only gas option. A 4s methanol engine will provide a superior power to weight ratio.Alternatively, get the 1.6 aize funtana and fit a DLE30.The 30cc gas engine range is where it begins for aerobatic planes

RE: Difference between Gas and Glow engines performance wise
 

Gas or glow is a matter of opinion they are both good at certain things.

Glow fuel is better at

powering smaller planes
More powerful than gas per cc
simpler in construction
easier to tune ( if you know what your doing )
long life span ( I am still running a Super Tigre "X" RE that I purchased in the 70s )

Gas is better at

cheaper fuel
Fewer off season storage concerns ( No rusted bearings )
cleaner to operate, your plane isnt slick with oil after a flight.
powering planes over 15 lbs

I have flown both and far prefer the power to weight ratios of the Nitro glow engines. My planes fly better with nitro power plants. Gas just isnt there yet for me. Once the designs are brought up to todays glow fuel performance standards then maybe I would switch over to more gas engines but the gas designs we see for the most part are pretty dated. The new OS 55 gas engine is an example of what we need more of. Very nice engine indeed. For the most part I have .60 to 1.20 Nitro engines and am very happy with them. They are reliable, never dead stick and other than the fuel clean up, have for 30+ years been my engine of choice............ No reason to switch..........

103/17

RE: Difference between Gas and Glow engines performance wise
 

I want to start and needle it with your feet.