Nitro?  We Don’t Need Nitro! (Part 2)

     This is to follow up on the(again)situation of Sig Manufacturing not being able to get nitro to mix fuel.  I have now flown in, and ‘trophied’, in two contests using zero nitro fuel that I mixed with methanol, from the local go-cart/motorcycle speed shop, and Klotz synthetic oil from Sig. (18% oil content).

     My Stalker engines actually run better on ‘no-nitro’, as the break into 2 cycle is not as abrupt.  On my .40’s, I removed .016 thousandths of head shims and have the same power as on 5% nitro fuel.  On my Stalker .66 I have not changed anything, and I finished 5th in Expert PAMPA at Brodak’s. (26 entries). At the NATS, if hotter, I may remove a shim or two.

You can compensate for lower, or zero, nitro in several ways:
(1)   Increase compression as indicated above. Removing .010 to .020     thousandths of head shims seems a good place to start.
(2)   Run a slightly larger venturi to allow more air(oxygen) into the engine. What nitro provides is oxygen…it is ‘chemical supercharging’
(3)   Run a little more prop pitch.
(4)   A combination of the above. 

     An unexpected benefit of running no-nitro, is fuel economy. Since the only oxygen source is the atmosphere, much less volume of fuel is needed to achieve the proper combustion mixture. In real terms, that means that I am burning 3.0 ounces of fuel where I used 4.0 ounces of 5% nitro fuel.  Some of you scoff and say “That is not enough fuel!”  well, if the engine is making power, and is cooling adequately, exactly what would be the benefit of running more fuel through it?  Anyhow, the Europeans have been running them this way for years.

     At Brodak’s I also talked briefly with Kaz Minato’s friend (sorry, I did not write down his name) who runs a Super Tigre .60 on 0% nitro with no problems.
     
     In a way, we’ve become ‘addicted’ or at least ‘dependent’ on nitro methane.  There is a long, long history of it being in commercial model fuels.  In stunt, where we can run virtually any size engine, nitro really is not a requirement…it’s a crutch.  It is handy to change nitro levels through the day as the temperature changes, and I have done that for years.  But it is not the only way to go.  In my Stalkers, I just don’t see ever using any nitro anymore.
     
     Oh, Sig can provide their ‘FAI’ fuel.  It is zero nitro, 20% oil, half Castor, half Klotz synthetic.  I sell it for $20.00 a gallon.

Tom Dixon   
06/21/2018

Trying to run FAI fuel in a conventional USA stunt engine is a precipitous reaction to one supplier not being able to make it. SIG may be out of fuel, but everybody else seems to have no problem. It will cost more, but minor tweaks to conventional setups WILL NOT yield the same performance.

   Some/many Stalker and other eastern-block engines are set up to run with FAI fuel, but most others are not. If you have one of these (like a Discovery-Retro), you should have at least started on FAI fuel, because thats what it likes.

The suggested "modifications" (some of which cannot be accomplished - how do I move .020 of head shims from my engine with a single .005 gasket) are in the direction of lower performance - more pitch and a bigger venturi? Good luck, now you have reduced the fuel draw (running lower RPM) and made the venturi larger (making it much sensitive)- and are running FAI fuel which makes the needle hyper-sensitive even with no other changes.

   You can certainly make a lot of modifications and get your engine to run OK (not well) on FAI fuel. Based on what I have seen over the years, virtually no one will be able to make these modifications without screwing up something else.

   No one actually needs SIG fuel, most people around here have long since abandoned it due to the tater problem. Get Powermaster, Rich's Brew, etc, and move on.

     Brett
   

I've mentioned numerous times that I've always mixed my own fuels. For those that do mix their own fuel getting nitro is a real issue. Torco started selling it again,but at around $80 per gallon to your door(I think) That's too expensive. I did recently obtain one gallon from S&W fuels for $50, but to be honest, he was reluctant to sell it to me. One other thing ,there is no money saved by mixing your own in small quantities. What you do get is the knowledge that the fuel has the correct ingredients and is mixed properly . ......Skip
PS, when not mixing my own, Powermaster is always good.

   Completely unnecessary:

https://vpracingfuels.com/rc-fuels/#aviation
http://www.ritchsbrew.com/info.html
http://www.byronfuels.com

and many more.

    Brett

 

     Not much help if you want to buy Nitro to spike or make your own. Two of those won't sell you nitro at all and the third will sell it to you but shipping and haz-mat will more than double the price.
     FEDERAL regulations on Nitro are driving most small speed shops and fuel retailers out of the fuel and/or Nitro business due to cost, red-tape, and Fort Knox-like security requirements. You have to be pretty high volume (of nitro) to amortize the cost. In addition, there are VERY limited places to buy wholesale and they take advantage of it $$$$$. You can buy several 54 gallon drums for around $1200 ea. trucked to your place of business (about $22 a gallon) if you have the money, a license, a federal approved storage facility, and the means to handle and distribute 55 gallon drums weighing 490+ lbs., but you don't.
     Buying fuel on line or by phone is pricy because you get hit for haz-mat and freight, unless you buy qts. then just freight but the fuel costs more. One of our local shops stocks Powermaster and even carries GMA blends but there's a catch; to avoid excessive freight + haz-mat, he has to buy it 16 (4 gallon) cases at a time. That's a substantial investment for a small return at a Mom and Pop shop. In addition, if he runs out of your favorite first, you'll wait months for the eventual restock.

Hi
In Ukraine, none of the Stunt pilots use nitromethane in fuel. Only methanol, synthetic 2-stroke oil Motul, Fuchs, Klotz, and castor oil.
Ukrainian engines for stunt models, such as Stalker, R&B, Discovery Retro are designed to work at low revs, with a conventional silencer and without using a resonant tube. For this, the stroke of the Ukrainian engines with the same volume is much larger. Propellers are also used. Much more diameter and pitch.
It's just a completely different way to achieve the same goal.
American pilots and engine manufacturers went a completely different way to achieve the same goal. They use short-stroke engines under the resonant tube at higher revs with propellers of smaller diameter and pitch.
In the engine Stalker 60 and Stalker 66 added nitromethane to increase power only in very hot weather +35 degrees Celsius and above.
The Stalker 76 engine is always in excess, even in the heat of +40.
In the Stalker 76 engine, nitromethane is not necessary to add fuel because of a very large excess capacity. We reduce the power in this engine by increasing the combustion chamber or by reducing the diameter of the suction nozzle of the air.
Nitromethane is sold freely in our country at a price of $ 25 per liter. All the pilots Combat buy it and prepare the fuel themselves with 10% Nitromethane.
Regards
Ruslan

... Some/many Stalker and other eastern-block engines are set up to run with FAI fuel, but most others are not. If you have one of these (like a Discovery-Retro), you should have at least started on FAI fuel, because thats what it likes. ...

Not meaning/wanting to start any sort of argument, just looking for information.

I have heard this same thing many times in the past: "eastern-block engines are set up to run with FAI fuel" and I simply don't know what that means. How is the engine different from an engine "set-up" for use with nitro? Is there some sort of structural change? Assembly procedures? What?

BTW, the term "FAI fuel" is mis-leading as well since at least in F2, two of the four events have no fuel specification, one is specified at 10%, and the last at 0% nitro. So, really, what IS "FAI fuel"?  (Oh, sure, I KNOW what you mean, but ....  )

I've mentioned numerous times that I've always mixed my own fuels. For those that do mix their own fuel getting nitro is a real issue. Torco started selling it again,but at around $80 per gallon to your door(I think) That's too expensive. I did recently obtain one gallon from S&W fuels for $50, but to be honest, he was reluctant to sell it to me. One other thing ,there is no money saved by mixing your own in small quantities. What you do get is the knowledge that the fuel has the correct ingredients and is mixed properly . ......Skip
PS, when not mixing my own, Powermaster is always good.

I see its already no longer available on eBay from Torco. That went fast. Glad I got the gallon when I did.

Chris

The first system works like nitro but is more laborious and less flexible, the other two have as fundamental defect the fact that they do not return a system that is always the same.
The engine will burn more fuel and will give more power on cold and dry days, while with very hot and humid it will be necessary to reduce the amount of fuel at the expense of power.

Massimo


P.S .: If I'm not mistaken "someone" on this forum often repeats phrases such as: "increase or decrease the nitro to have an equal fuel consumption" ......

   Indeed, someone does. The point of that is to prevent the issues you are discussing, i.e. loss of power when it gets hot and humid. and generally retaining the same engine settings, prop, venturi, pipe length, tank, regardless of the conditions. Change the nitro to match the fuel consumption, and more-or-less, you get the same power, the same duration, the same temperatures, etc. If you only run FAI fuel, or attempt to only run a single fuel (say, you standardize on 10%), when you get a sufficient change in the conditions, you have to make changes all over the place much like Tom suggests. The problem being, of course, that you have a finite amount of time to do that, and most people would be far, far better off if the engine manufacturers welded the heads on the engines so that they *couldn't* be taken apart to fiddle with them. They way most are set up, for 10% in the Midwest, you would need to have the NATS at a sea level site in Antarctica to make FAI fuel the right choice.

  Making the venturi larger instead of adding "liquid air" in the form of nitro has the effect of reducing the fuel draw. The loss of power and the extra pitch you will have to probably run (to make the prop more efficient to make up for the loss of power) will probably make you run it slow, further reducing the fuel draw. That's why the engines get so touchy on the needle as you reduce the nitro.

  This also explains why almost everyone who has gotten Stalker engines in the USA have had problems, particularly with the 61. It's very difficult to even find someone who knows what FAI fuel or "no-nitro" fuel even is, the clerks at hobby shops call glow engines "nitro motors" most of the time. It's sometimes hard to find 10% and 5% is rare, although you can order it. 15-20-30-40, no problem, there are gallons of it at any hobby shop.

For example:

    https://stunthanger.com/smf/engine-set-up-tips/stalker-61-in-arf-score/msg25045/#msg25045

   So yes, it can be made to work, with special fuel, special techniques, and a lot of knowledge. And then you wind up with 6" of pitch or more, and 4-2 break or a steady 2 or 4. Congratulations, that's the hot setup to win the 85 NATs. Too bad its 2018.

  I think converting to electric in the next two weeks would be more likely to work and more likely to yield a competitive package than attempting to run FAI fuel in a typical US stunt engines in the next two weeks. But getting fuel *somewhere else*, like the 6 gallons of 10% I bought last weekend, seems even more practical a solution to this "problem".

     Brett