bako

hello everone, I have tryed to operate my magnum 91RFS on ) nitro fuel, I removed all shims from head, installed hot plug, readjusted needles, but ideling isn't as slow as I want. some people talk that they achieved good operation from 0% nitro fiel. yes, mu top end is stabile and well, transicion is good too, middle is good too, but ideling is too high.
maby I need to install remote driver, which cinematically will be turned on on low rpm?

wcmorrison

My Feedback: (2)

The nitro in the fuel helps the idle. But yes, if you are not going to use any nitro, then a glow driver may help keep the engine going at a low RPM. Otherwise, go down in pitch on your prop and that may help you with lower landing speeds, if that is you problem.

Magnums are not known for good low idles either. OS will idle lower.

Good luck,

Cheers,

Chip

Campgems

Chip, I have to disagree on the Magnums not idleing as low as the O.S. engines. Granted that I have a Mag 52 that is giving me idle trouble, but I've got two of the Mag 91's and they will tick over at 1800 for a minute or more and then jump to life when asked. I have a Mag 70 that runs the same. There is little difference between the two engines, at lease in the 52 size. I have two O.S. 52's and the only real difference is the carb. On the O.S., the idle jet is on the same side as the high speed, a nice touch for cowled engines. The larger ones though, there is no difference.

One big thing on the idle though is the nitro. I run 15% Omega and it runs just great with no modifications to the engine. Bako, what are you trying to accomplish by using 0% nitro? The 0% fuel is harder to find in the LHS, and if you do find it, it may not be fresh. The buck or two a gallon dollar savings arent' very real when you have to add batterys and controllers for onboard ignition. Just my 2cents worth.

Don

AMB

All my 4 strks Saito, Magnum, and 0S do fine on 10%, using less nitro than 10% makes staying lit and transitions much harder I really find 10% is enough have used 15 % but 10 works for me martin
one of my ASPs same a magnum 52 4 strk no issues converted over to diesel for me by gkamysz

rchotrod

I would replace the shims and put the needle setting back to the manual settings. Removing the shims raises your compression ratio.

Watch your idle mixture screw closely. It will back itself out over time, changing your mixture. You may need to replace the little o-ring on the low end needle.

Different props will also affect idle. You could try a heavier nose cone or add a cone weight. It will act as a flywheel and help the idle, but will take the engine longer to spool up.

I have a magnum 52 4-stroke and it idles great, not sure how fast. I am running the Cool Power 15% 4-stroke fuel spinning a 13-6 wood simitar(?) profile prop. Even my 2-strokers like that fuel. With that prop I can idle the engine and it won't roll in the grass but it will on a paved runway. If I went to a 13-5 it might get better. But that is for my plane, a Blue Max. A big ol' fun flyer. Your plane may need a different prop.

Is this a new engine? It may take a gallon to get the engine worn in enough to idle that slow.

An on-board glow drive will help, but that can also mask poor engine tuning.

See ya,
Rod

downunder

Bako isn't from America so like for the rest of us non-Americans nitro is very expensive.

Removing shims doesn't raise the compression enough to suit straight methanol because ideally it should be up around 13.5:1 for best results. Early Saitos were up around 15:1 but Americans like to use nitro so Saito had to reduce the compression. Machining is the only way to raise it high enough but valve clearance from the piston has to be watched very carefully. A slightly longer conrod is one way to do it .

Personally I'd opt for the idle glow driver if that's the only area that needs attention.

blw

My Feedback: (3)

I've read of some other countries where nitro is inexpensive. Always glad to hear about anything that is priced reasonably.

AMB

Just messing around about a year ago. I fed one my 4 strks magnum I think, a diet of FAI fuel on the bench. It lit right off from half to full throttle no issue, less than that and it died
without the glow hooked up. so an on board glow would work. I never proceded however and went to 10% nitro martin

bako

thanks people!!! as downrunner said, I'm not from america, I'm from republic of Georgia and we have only electric rC shop here, it means we have no fuel dealers!!!!!!!!!!!!!!!! I make homebrew with methanole and castor, but can't get nitro. that's why I'm trying to operate engine on 0 nitro. when I was learning in Kharkiv(Ukraine), I was using 12% nitro fuel from graupner and I was happy with it. but now

Campgems

Sorry for the misunderstanding, I saw Georgia and though it was the state of Georgia.

Guys, is there any other aditive that could be used in place of the Nitro? Or maybe a different glow plug? Just curious.

Don

fiery

My Feedback: (2)

LASER engines are the only "off the shelf" four strokes that operate reliably on Nil nitro fuel, to my knowledge.

speedster 1919

My Feedback: (3)

3-5% acetone will help and oil % will make a difference. When is the last time you checked the valve clearance ? I run everything I own on 5% nitro 2 and 4 stroke. I went to no nitro and 5% acetone and was surprised on running. Acetone improves the cold weather starting. Your using 100% castor so 17% total oil would work...........

NM2K

My Feedback: (14)

You beat me to it, Speedster. I was going to suggest a bit of acetone in the fuel too.

We Americans are spoiled by using nitro in our fuel. Running no nitro really forces you to pay attention when tuning. Also, you will notice a much larger improvement in how the engine performs as it accumulates running time. Nitro tends to cover this up, so folks think the engines are broken-in when they truly are not quite there yet.

None of my Magnum four-strokes performed as well at idling low as my OS four-strokes. But, again, it is probably due to the fact that I didn't accumulate that much running time on them, whereas the OS engines are closer to being broken-in right out of the box. It will be interesting to see how this turns out with my two World Models Intruder 90 SPA pattern ships - one with a new OS.91 pumper and one with a new Magnum .91 four-stroke. I just wanted to see how they compared after a while. I do not expect the Magnum .91 to produce as much power as the OS, after seeing the SPA article showing the size of the valves in both engines' cylinder heads. The Magnum valves are quite a bit smaller than those in the OS FS-91.


Ed Cregger

rchotrod

Will the idle bar plugs work in a 4-stroke glow?

But I bet the on-board glow driver would help in idle. Looks like you pretty well got the engine tuned. Maybe adjust your mix alittle.

Hope you get it running better.

See ya,
Rod

blw

My Feedback: (3)

Ed,

I'm not sure that article was objective.

Flyer95

My Feedback: (1)

3-5% acetone, eter or gasoline should help with idle. I tried 5% acetone and 5% gasoline added to my 0% nitro fuel för my Saito 180 in cold weather a few years ago and it ran very good and idle was low, below 2000rpm. However the idle mixture must be retuned if your engine is been running on 12% nitro before. You must lean the idle mixture for the no nitro fuel.

blw

My Feedback: (3)

Bako,

I'm not trying to push nitro, but do you have any motorcycle or car race shops near you? Sometimes, you can get nitro in those performance shops.

Saitos will run fine without nitro. Not as well as with at least 5%, but they will run. A lot of people use low nitro for help in smooth running, not just for power increases.

Campgems

Ed, the bigger valves would give an advantage to the O.S on power. I havent pulled the head on my Mag 52 to get an idea of valve size, but I did unintentionally pull the head on one of my O.S. 52/s a couple months back.

I am rebuilding the carb on that engine with a new housing and am going to put it on the Mag 52 so I can get a comparison in performance. Seeing as a trashed my 52 size plane, it will be a bit before I have a test bed for the comparison.

On adding acetone, has anyone adding a bit to nitro based fuel for improved idling? Also how does the top end and engine life compaire using the acetone? This thread it turning up some great info.

Don

bako

hello people!!!
I made a glow driver, which heats the glow plug when throtile is decreased more than 2/3 from full.
OH MY GOD!!!!! it's anothen engine!!! I retuned needles and made video, how I tune it. the video is with finger pointings up or down, marking I'm going to lean it or to richen it up.
sound is poor, cause MY mobile phone was in the room and planes has been shot from window, but u can mention how low ideling is!!!
tomorrow i'm going to fly and I'll see on tachometer how low it goes.
I think I went on a bit leaner side at the end of the video, I'll ritchen it up a bit
there is slot for one AA size battery, I use now 2000mAh nimh battery. I think it will be apsolutekky enough for 1 flight including the fact, that even on half throtile it doesnt heat the glow plug.

http://www.youtube.com/v/U_dzjHOJVNY

Flyer95

My Feedback: (1)

The idle in the video looked smooth and low. I would leave it there and set it always slightly rich to have some margins for when the weather changes and gets colder the engine needs more fuel.

NM2K

My Feedback: (14)

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I never questioned the objectivity. Care to elaborate via PM?


Ed Cregger

NM2K

My Feedback: (14)

[quote]ORIGINAL: rchotrod

I would replace the shims and put the needle setting back to the manual settings.


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There are no manual settings in any real sense, Rod. CNC machining hasn't come that far yet. Why? Because not all needles are made during the same run, as not all needle valve bodies are made during the same run. Differences in material, temperature and machine operator can make a substantial difference in parts that are supposedly "identical".

Then we run into issues such as fuel tank height, size, elevation of the operating location, glow plug choice, prop size and least of all, the fuel being used. All of these factors mean that the settings listed in the owner's manuals are only very loosely recommended starting points. They are not etched in stone, not Scripture from on high, etc.

If you already know this, then ignore it. But there are many thousands of folks reading RCU that never utter a single printed syllable during their whole RCU lifetime. Some of these folks need to learn "THE TRUTH". if you catch my drift.


Ed Cregger

NM2K

My Feedback: (14)

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I have used idle bar plugs (Fox R/C Long) in four-strokes before without glow driver assist and they can work in a pinch, but not anywhere near as well as an OS Type F or an Enya #3.


Ed Cregger

NM2K

My Feedback: (14)

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They used to run very well without nitro, until the folks at Horizon began talking people into running 30% nitro in their helis and 3D models.

You see, 30% nitro widens the prospective number of customers because it takes less tuning skills to run the engine properly. Good money move on their part, but a bad move for the rest of the world's modelers. But what do they care? They're in it for the money - as any business should be - to a point. We can change the point by insisting that our engines run without the expensive nitro crutch. Why should we do that? Because it improves engine technology and design. For engines to produce the power we need on 0-5% nitro, they must excell in engineering, not on expensive fuels. Modelers benefit world over, not just in the US where nitromethane is cheap.

Duke Fox used to set up his engines to run on his Missile Mist (R/C engines at least). I talked to him on the phone and challenged him to make his engines run just as well on 0-5% nitromethane. I more or less dared him to, knowing full well that he could. Danged if he didn't take the bait and made the switch.

He asked me why I was so against using lots of nitromethane. I explained that if I buy a more expensive engine that runs well on no or low nitro, then when it comes time to trade-up (I was a competition flyer then and needed the latest engines), that I could recover much more of the cost of my engine due to the higher resale value. But, if I used an inexpensive USA engine that burned very expensive fuel, the resale value was seriously depreciated and all of the expensive fuel that I paid for was simply blown out of the exhaust port, never to be seen again. It seems that he took my argument to heart and then proceeded to develop a low/no nitro head for the Eagle .60 (baffle piston engine) that he was currently producing. I had been a customer of Duke's since the sixties and I'm still a true believer in his engines.

I can actually tell when a Fox engine is flying around overhead just by its sound. Duke's engines have a characteristic sound that his timing/porting imparts to his engines. I miss the old guy and was proud to have known him (albeit casually via telephone).

Ed Cregger

blw

My Feedback: (3)

Using nitro is a matter of choice and opinion. I wouldn't say anything against either way, and certainly wouldn't call using nitro a crutch. I don't care to use more than 15%. That is what is commonly available in my neck of the woods. I had a chance to pick up a case of 30% for $40 the other day, but didn't see the need for it.

While I personally don't want to use 30% for SPA flying, those guys believe in the extra 300 or so RPMs for competition. There is a place for using it for some people. Then, there are the speed demons who will do just about anything to fly faster.

The best thing is to let people have fun the way they wish, and not make judgements either way. Saying that nitro is a crutch, or that it is pushed on the market to make money off of people isn't right. Some people enjoy it. Simple. Just like some people enjoy running their engines without it. It seems to me that we only hear about the American market demanding engines that run better on nitro. The other side of this is the need for FAI fuel for contests. I don't like the 20% oil rule, but I wouldn't want to make an issue out of it. Live and let live is the best policy.