T28pilot

My Feedback: (2)

Do we really need nitro?
just wondering....
can i run F.A.I fuel in my planes?
0% nitro......i do religiously in my MOKI's
But what about my other motors???
i got a motor that calls for 5% for break-in will it run on F.A.I. fuel?
Is the nitro there just for more power??
Or do these motors NEED it??

any help would be apperciated!!

Homebrewer

My Feedback: (8)

Can we live without it? Depends...

I don't understand why RC in USA is addicted to Nitro. As a result, engine manufacturers have designed their engines to take this into account. Maybe they got an agreement with the fuel makers who knows.

Now, why do I use 15-20% nitro in my engines? Because the engines I buy are low compression engines and need it.

If you buy a high compression engine you can get away with using little, if any. Unfortunately, you won't be able to buy OS and other popular brands.

Many of the European engines are high compression and are designed to run on FAI fuel. If you put nitro in them, you'd suffer from detonation. You can add head shims to a high compression motor to reduce the compression ratio and than you can use the nitro and possibly develop more power. To do the opposite to a low compression engine such as an OS .46 would take some more work such as milling head and/or messing with the squish band.

Nitro has its advantages though but I think we Americans have fallen prey to marketing..

Fuelman

My Feedback: (6)

Homebrewer hit it right on the mark, good job!

Dave Gierke wrote a book "2-Stroke Glow Engines for Aircraft". He goes into detail explaning the relationships between nitro, compression ratios, glow plug heats and port timing and how they are all interrelated. After reading all his publications over the years and talking to him on many occasions, it all comes together and is actually simple to understand.
Once the concept of high compression = low/no nitro, low compression = some or high nitro. The relationship is not always arithmetic depending on many other factors involved with the engines design. Some lower compression engines will run very well on lower nitro if you put in a hotter plug. Some OS 2-strokes will run quite well on 5% or less when you remove the head shim and again, use a hotter plug.
Rossi's & MVVS' for instance, love 0%-5% nitro, high oil fuels, and actually start getting problimatic above 10% nitro.

NO, the engine manufacturers are not co-conspiritors with fuel manufacturers just to drive prices up. Americans and a couple other countries just like to use nitro in the fuel. It goes back a long time to guys like Dave Geirke, George Aldrich and many other icons of model engines when they kept trying to go faster. So engine companies designed engines to suit our tastes.

Great question, good one for a FAQ page.

Fuelman

T28pilot

My Feedback: (2)

But now on to the Question at hand here......
Will it be ok to Break it in on 0% when it is calling for 5%?
Will It run at all?
The "it" in this senerio is a Thunder Tiger Pro .70
It is in my new R/C Truck....
they say it is their helicopter motor......
Would 0% be ok?

Homebrewer

My Feedback: (8)

IF your engine is ABC/ABC type (no piston ring) you should break in using the highest nitro called for.


If your engine is ringed no harm in starting off with low nitro but you really should break in under the conditions that you will be operating under. Switching nitro may require some time for engine to adjust to the higher temps.

T28pilot

My Feedback: (2)

And they call to break it in with 5%.......Don't have any 5%
and at this time of year i doubt my LHS will either......
But i got alot of 0% and 10% and 15% and 20% and even some 30%......but they are talking about running up to 3 gallons thru it during break in and i'd rather pay 9 bucks a gallon than 15 or more for the higher nitro fuel during break in.......
i mean all were doing here is seating the rings......

Ed Smith

"i mean all were doing here is seating the rings......"

This statement could not be more wrong. It never fails to amaze me that people spend hundreds of dollars on engines, many engines, and then proceed to destroy them by following some misguided internet raving on engine break in.

Forget most of what is posted on these forums. For the cost of less than a couple of gallons of fuel there are two books available written by acknowledged experts. "Model Four Stroke Engines" is written by Peter Chinn. "Two Stroke Glow Engines, for r/c aircraft" is written by David Gierke. Both books are published by Model Airplane News.

Instead of wasting money on fuel by the "Slobbering Rich" break in method, buy the books. Then read, mark, learn and inwardly digest. Stop destroying engines before they even get into the airplane.

Ed S

Homebrewer

My Feedback: (8)

Ed,
I hardly call anyone who writes for MAN an expert. Have you read any of their crap lately? I have yet to find a review that actually is truthful about the deficiencies in a kit/ARF/or engine.

Running a ringed engine slobbering rich will not damage an engine one bit. Running an ABC/ABN engine will. Please avoid the generalizations about the advice posted on the this forum.

Ed Smith

HB,

I did not suggest you buy M.A.N. magazine. I do not subscribe to it for the same reasons. I was merely pointing to the source of the two best engine books I have read.

You tell me not to generalize then you write this "Running a ringed engine slobbering rich will not damage an engine one bit."

After you have read the books you will realise how much well intentioned but bad information is being read by people trying to learn.

Ed S

I am finished on this subject. I have books to read, written by people with real knowledge.

downunder-RCU

Well the first thing is that FAI fuel strictly speaking is 80/20 all castor, no synthetics but nowadays it's being used to mean any fuel with zero nitro.
I'll say straight off that ANY engine will run quite happily on FAI type fuel. Nitro is in general use in America because compared to anywhere else in the world it's CHEAP! And why is that? Because it's only made in America!
The old Fox35 had a C/R of 5:1 yet it didn't need huge quantities of nitro for it to run. Most modern engines run somewhere around 9.5 to 11:1 C/R and this includes European engines.
There's very little difference in the running temps between FAI and nitro fuels, in fact if you go to this link http://www.modeltechnics.com/glowplug/firepower.html you'll notice that using nitro in most cases actually results in a lower temp (higher fuel flow gives more internal cooling, to keep it brief). There's likely to be a greater difference between running your engine in winter or summer, full throttle or idle, large prop or small prop.
You'll get some increase in revs using nitro but you have to weigh the increase against whether the plane flies noticeably better, the added cost of the fuel and the increased fuel consumption (which adds further to the actual cost).
As for breaking in your ringed engine, collective wisdom over the last 60 years or so says to run it slobbering rich. And use castor (or at least a 50/50 mix), this will protect the critical rod bushings because they're part of the running in process. Ringed engines do take much longer to run in (ST for instance say that it can take up to 15 hours) but the end result is worth it.
Oops, just noticed your engine is going in an R/C truck so ignore the bit about flying better

Fuelman

My Feedback: (6)

T28,
I can respectfully agree with Homebrewer, According to conventional and collective wisdom as gathered over many years of modeling by Experts such as the late George Aldrich and Dave Geirke. That wisdom is well described in Dave Geirke's books and homebrewer hit it right. Seating a ring will need to have an extremely rich setting, slobbering if you will. It will need to be heat cycled which is run three or four minutes and shut down to cool off. Read the book for more details.
My experience with Thunder Tiger engines is with the ringed 120.
After a carefull RINGED break-in with low nitro fuels (I used 5% nitro, 10% castor and 10% synthetic), after three gallons on the bench, I was able to start getting to where it would hold a max rpm setting for 30 seconds or more without sagging- sign of an engine ready to fly. I then ran a couple tanks of my flying fuel which is 10% nitro, 18% synthetic and 2% castor to fine tune my needles.

TT engines will reward you with a fine running reliable machine if properly broken in to type. Yes, 0% nitro is fine for break in, but looking at your post above, you can make your own 5% by mixing equal amounts of your 10% and 0% fuel. Please insure that your fuel contains 20% lube (preferably some castor), and DO NOT run any fuel on the market labeled "Buggy/Car", most of these fuels (CCB Fuels being an exception) do not contain enough oil for this engine. Your engine is a Heli engine and not designed to be run on traditional low oil buggy fuels. After break-in, run a heli fuel if you desire but never a low oil fuel. Remember to use the air filter. Thunder Tiger's are fine engines and I run them often.

For more information please e-mail me directly.

Fuelman

T28pilot

My Feedback: (2)

I went ahead and ran two tanks of F.A.I. fuel thru it.......As Rich as it would run.....Which is about 3 to 5 minutes before it loaded up and died.....outside here in illinois when it was about 35 or so degrees.......also with the body off so it could get as much cooling as possible.....then went to 10% rich's brew fuel.....for three more tank fulls.....just idleing around in the barn lot......on the 4th tank i leaned it out just a tad...but it is still rich as heck.......now should i keep running and leaning it out till optium performance?......or keep it really rich for a longer time?

I can sure tell that motor is going to be a strong one so that is why i am trying to get this as right as i can!!

gubbs3

My Feedback: (1)

As a former R/C car enthusiast, I know there is way too much mumbo jumbo out there about break in. I have heard everything from running at idle and not going over 140* degrees to running wide open at slightly higher temps than what will be normal.

The best running engine I had, I ran three tanks at high idle around 200*. Then I ran slow for three more at the same temp. As the engine was breaking in the temps will go down. You must keep them up or nothing will be accomplished. I ran at 200 for about 1/2 gallon (this is a .12) and then leaned it out to 250 for two tanks for a finial loosening up. After that it was the fastest thing I had ever seen running at 210*.

Most airplane guys might not get all this since plane engines run differently and temperature isn't used as a tuning tool.

Use the fuel that is reccommended, end of story. If you use less nitro you won't get enough heat unless you lean it out too much to the point where you won't get enough oil.

Even though the engine in your truck is a heli engine, it's not in a heli, so treat is like a car engine. It would be a good investment to a get a temp gauge or gun. For best life, don't run it above 250* and keep it above 180* during break in. Good luck.

Moore-VARIO

While brousing Rotory Modeler Magezines' website, I copied this article to my clipboard a long time ago.

>>

HIGH PERFORMANCE HELICOPTER FUELS
Nitromethane: can truly be deemed "Liquid Horsepower" for model helicopters. For additional power and generally smoother running, our flying machines can't really afford to live without it!
If the engine performance of your R/C helicopter is proving to be a bit of a problem for a whole tank of fuel, and you suffer from overheating as the tank empties during hover, or the idle is difficult to get "just right", it may be that a dose of good old fashioned "nitro" is what the engine doctor would order.
Nitromethane is a liquid that has been around for a long time and is used to contribute towards smoother running and increasing power in varying amounts of many model fuels. In addition to altering the power output of an engine, it also contributes towards cooler, cleaner running, smoother idling, and easier starting. Of course, the positive affects of nitro must be weighed against the cost of the magic liquid, which can add from $2 to $4 per gallon per 5% of nitro.
Other than the plain fact that nitro is probably the easiest way to increase the power output, or smoothen the run of a model aircraft engine, the whys and wherefore's of nitro are not well understood by most modelers (or anyone for that matter, based on the trouble I had finding information on the subject) so what follows will attempt to shed light on the mystery and help heli flyers decide whether they need use it, and if so, how much.
Nitro is manufactured in production volumes by mixing nitric acid and natural gas (or other hydrocarbon base) under high temperature and pressure. It can be made in the laboratory by some complicated mixing and distilling of acetic acid, sodium carbonate, and sodium nitrate which is rather hazardous.
The element that is most important is the oxygen which "disassociates" from the liquid at high temperatures. While Methanol has almost the same amount of oxygen (50%) by weight, it is the overall "mix" that contributes to the unique nature of nitro, allowing a much higher fuel flow and the typically inert nitrogen which can serve to "soften" the shock of the combustion process and inhibit pre-ignition (this is not to say using nitro prevents pre-ignition).
All fuels, whether gasoline, methanol or nitro (which incidentally can be burnt at 100% mix like most fuels) have a "stoichiometric" (I brought this word in in a wheelbarrow!) or chemically correct air to fuel ratio, at which they theoretically (as calculated by chemists on paper) burn the most efficiently in air. With gasoline it is 14.9:1 (air to fuel) with best power at 12.7 and best fuel consumption at 15-16:1. Gas puts out 2.78 kilo Joules of energy per kg. Stoichiometric methanol burns best at 6.5:1 or twice the liquid (by volume) for the same amount of air as gas and produces 2.67 kJ per kg, slightly less than petrol, but typically produces 10% more power due to the temperature drop of the mixture as it vaporizes, which produces a more dense mixture (higher density = more power). Methanol burns twice as much liquid as gasoline because it carries its own oxygen supply along with it (50% by weight).
Methanol can also run 40% rich and still make good power because of this. This excess fuel contributes to cooler operating temperatures. Nitro burns at a big 1.7:1, or 37% liquid, 63% air, or nearly three times as much liquid as methanol. Energy at stoichiometric = 4.05 kJ per kilogram or 1.5 times that of methanol. This is where the effects of nitro become important.
Getting fuel into an engine is never a problem. The problem with producing power from a given engine is getting the air in! Hence, the use of superchargers, turbochargers, special manifolding, porting and valving arrangements on modern car engines.
With model engines in general, we don't have the luxury of supercharges, etc. (the 0S 120 Supercharged four stroke being the exception). So Nitromethane actually provides "chemical" supercharging, introducing up to 3.8 times more liquid overall or 5.5 times more oxygen per liter at 100% "stoichiometric" mix, meaning more fuel (methanol) can be burnt, because of all the extra oxygen (the oxidizing agent).
For example, a methanol only mix provides 400 grams / liter of oxygen (gasoline has zero oxygen). At 20% nitro, there is 3.14 kJ/kg of energy and 436 g/l of oxygen, and because at 20% nitro the correct mixture or air / fuel ratio is about 4.2:1, a 35% increase in fuel flow will occur, which means around 47% more oxygen ends up in the engine when tuned correctly.
I know this sounds complicated, but I did check my math repeatedly, and it all makes sense if you remember that we are talking about quantities here in two different situations: specific quantities per liter and quantities per liter at the "stoichiometric" mixture fuel flow!
This increase in oxygen availability and fuel flow amounts to richer running. For example, the main needle has to be opened further to flow the correct amount of liquid to match the incoming air (which is pretty constant at any given throttle opening / rpm level). This also means that the tank may last up to 35% less than with straight methanol fuel. If you get 20 minutes with "straight" fuel, 20% nitro could only last 15 or so minutes. (In practice this is not a linear relationship. With more nitro, typically a smaller throttle opening is needed for the same amount of power, i.e. at hover. So it's generally more than 15 minutes mentioned here but less than the original 20 minutes.)
With all this extra oxygen and fuel going into the engine, more power is available, as mentioned before, up to 50% at 80% nitro has been measured. So for every 5% nitro, a power increase of about 3-4% might occur if everything is adjusted correctly. Of course 3% is not much, but at 30% nitro which is common in the USA and Japan in choppers 15% to 20% power increases are easily within reach.
More power equals a higher combustion pressure which equals more heat! Cooling: Of course with 42% more liquid going through the engine at 30% nitro much more heat can be soaked up - liquid absorbs heat much better than air. There is also 42% more oil going into the engine, almost flushing the internals continuously, which also helps take out more heat. So we have internal liquid cooling! All this extra liquid keeps the metal surface temperatures down and eliminates the burning of oil to carbon. So there are usually little or no carbon deposits in nitro fueled engines above 10% nitro.
The cooling effect of nitro is further born out by the increased usage of high nitro fuels in fuselaged models which are almost totally enclosed for drag minimization. The nitro is used just as much for cooling as it is for good power!
Nitro won't necessarily work the same wonders in engines from different manufacturers. Typically the Japanese have been heavy nitro "users" and produce engines which work well on high nitro and have relatively low compression ratios. In contrast, the European manufacturers, with nitro being more expensive and hard to get in Europe (not that it is all that cheap in Japan), appear to have engineered their engines with higher compression ratios for little or no nitro usage. It is not unusual to have to "decompress" European engines for satisfactory high nitro operation.
Nitro may not tune the same on different engine types, even from the same manufacturer, because the combustion process in a glow engine is triggered by a catalytic reaction of the compressed mixture with the platinum compound of the glow plug. Many different factors affect the "timing" of the ignition of the fuel / air mix (i.e. fuel quality and mixture setting, ambient air temperature, engine temperature, fuel temperature actual compression ratio, inlet & exhaust timing, muffler/type, etc.). This is in contrast to a gasoline spark engine where the ignition timing is influenced predominantly by the spark timing, which can always be optimized for best engine running at any rpm.
Further, the tuning with nitro can also be affected by the ability of the carburetor to deliver the fuel in sufficient quantity/accuracy thru various speed ranges. On some engines, the engine may not run well in hover above, say 12% nitro, but merely changing to a different carb, with better mid range flow adjustability may fix the problem.
Also, too high a compression ratio with too much nitro may have combustion on the edge of pre-ignition , and cause unreliable running and may be difficult to tune. Decreasing nitro content or decreasing compression ratios may very well cure the problem, as trying glow plugs with different heat ranges.
Hooked on Nitro: Many people will have heard that some engines are "hooked" on nitro, i.e. on nitro they run great, straight fuel they run like a dog, or have less power. While not necessarily "hooked" on nitro, they are used to running at a particular temperature, and all the clearances (especially piston to bore clearance in an ABC engine) in the engine are run in at that temperature. Changing the nitro content changes the operating temperature and you have a different engine on your hands.
While researching this article it became evident that information on nitro is very scarce. So if anyone out there has more information or would like to comment on or "discuss" any part of this article, please let me know c/o Rotory IAN McDONALD

>>

downunder-RCU

I'd wear a flame proof suit before I tried that
There's a fair chance the tank would explode..pure oxygen is extremely dangerous around combustible materials.
What has been tried (long ago in CL speed) was to have a seperate O2 bottle that fed into the venturi but this was banned very quickly as being far too dangerous.
Do us a favour and don't be a contender for the Darwin awards

downunder-RCU

Oxygen by itself doesn't burn...it's only when it combines with another substance that heat is produced.
I understood what you were thinking of doing, basically trying to dissolve oxygen into the fuel much like CO2 is dissolved into Coca Cola, but assuming the vapours didn't explode while you were shaking the tank then very little (if any) oxygen would dissolve.

pietermx

Glow fuel without nitro is like beer without alcohol.

Marc Trudeau

I know from running diesels that smaller props allow the engine to turn faster, but require timing advance (more compression, leaner mix, or some other source of heat), so ignition starts in time for the fire to be in progress when the piston passes top-dead-center. Similarly, larger props will turn slower, so the timing must be retarded (reduce compression or run a richer mix).

Can anyone lay out the related equation for glow engines?

My guess is smaller/lower pitched props need timing advance (more heat; so add nitro, remove head shims to increase compression, run leaner, or use a hotter plug). Larger or higher-pitch props need retarded timing (less heat; so reduce the nitro content, add head shims, run richer, or use a cooler plug).

Have I got it right? Especially, have I got the nitro change right, or do I have it exactly backward?

Thanks in advance to those more knowledgeable,

Marc

canadianjosh

gasoline engines for the most part use spark timing to time the explosion of the fuel/air mix. But in high performance engines fuel/air mix can ignite early due to high compression, also known as "knocking" this is why they use higher octane gas. ie 116 octane vs regular 87. I like to call r/c engines high performance because of the amount of power potential outof such a small displacement. As for the breaking in period, this is so that the separate parts can adjust to work with each other, things like the piston and either the sleeve or the rings will adjust to small small imperfections in the boring of the cylinder. In 4 stroke engines the pushrods will adjust to the cams and so on... It is impossible to ruin an engine by running it really rich. The onlything that this will hurt is your wallet. By running an engine rich it will run cooler, opposed to running it at peak rpm by leaning it out. In the summertime especially you should increase the oil content a bit and richen up the mix because the added heat of the enviroment and the running of the engine can cause it to cease. As for breaking in an engine with 5% nitro, when you only have 0% and 10%, just take equal quantities of each and mix them.

Relfy

I own a raptor 30 and have just clocked up 40 hours flight time. I use 10% Model Technics E.D.L. Oil with 2-3% Castrol M and an OS No. 8 Plug. I refuse to use Nitro and believe that it is not necessary, often causing a few raised eyebrows. The engine has never stopped, get's great economy and runs extremely well. I am now on my second plug. I have used this oil/fuel mix for 14 years in aircraft including my OS 46FX which runs bettter that any other OS46 at the lying field by far. I am converting everyone who tries this blend. My OS46FX has never stopped and starts first flick every weekend and I estimate that I get about 30% better fuel economy.

The secret lies with the oil. A friend told me that he uses 20%nitro in his JR heli cause it needs it. I told him that i never use nitro and he laughed at me. He has just replaced his piston/sleeve and bearings whilst my engine is remarkably clean inside and you can see the oil oozing out of the bearings. Nitro....yuck!

Give it a go, you will be surprised!

fancman

My Feedback: (16)

Canadianjosh.

If you run a brand new ABC engine very rich you will indeed run the risk of ruining it. Ask any mfg who makes them.

zaremba

Sir, are you implying that running the first gallon of fuel through the engine with it set "slobberingly rich" will harm the engine?

I'm not challenging you; I'm merely concerned that I did just such a thing with 10% nitro castor Omega, and worrying about having harmed my TT .39.

Thanks,
Paul

jetpack

My Feedback: (1)

I'm preparing to break in a Webra ABC engine, and the instructions call for a run-in mix of (true) FAI at a needle setting just breaking into two cycle, and a total break in time of 30 minutes, with varying speeds.

After break in, I can add synthetic and nitro. This is going against the grain of many here but thought it would be interesting to point it out. Webra seems to have a pretty good reputation in motors, and I guess trust them with what an ABC should experience.

I included the fuel table and reference notes from their website.

One question that I was searching for when I chose this thread is what is the best oil mix (or no oil mix) to use if you want to have the longest life out of a motor, ignoring the "high-performance aspects of nitro" and just sticking with the best oil mix and good old methanol.

Is it safe to say by just running Grade AA Castor is number one, and only goes downhill from there when you start adding synthetics?

Is there a thread started on this somewhere? I looked through the entire FAI threads and only found this comming close to the wear issue. I guess this is more of an oil question than anything.

I want to keep my motor going as long as possible, as it is now long outdated but still new and has turned into one of my gems, and get a good handle on what to put through it for fuel to keep it safe and happy. It is a large enough displacement for my application to where the power of nitro would be considered excessive, and the engine is designed around FAI fuel.

Sport_Pilot

Actually all of the Mfg. instructions I have read says to run them very rich. I don't see any saying to run lean or even slightly rich, usually as rich as possible without four stroking. Which is very rich since most do not easily four stroke.

downunder

Those instructions sound spot on. On the first start when you go to full throttle, if the engine sounds a bit lean then go back to part throttle and open the needle some more and try again. It's better to be 4 stroking rich than too lean. When you get close to the 30 minutes you can start leaning it out a bit but still keep it on the rich side. For long life I'd stay with a minimum of 20% oil and personally I'd use all castor but so long as there's a reasonable % of castor in the mix you should have adequate protection against rust and lean runs.

Actually I've never yet come across an engine that won't 4 stroke quite easily, in fact I fly my Rossi 45 in a 4 stroke in level flight so when it goes into a manoeuvre or steepish climb it leans out into a nice 2 stroke.