OS 4 stroke 20% nitro.

[Engine Doctor]

10 hours ago, Jesus Cardin said:

I ruined my vintage OS 40FS using by error a 16% Modeltechnics fuel, so I personally do not recommend going over 10% on OS Engines.......

Just out of interest In what way did it ruin it ?

[Paul De Tourtoulon]

Some of their fuel didn't have much oil in it, or was it running too lean ?.

[Cuban8]

Just imagine if you had all this fuss over fuels and oils with our cars - funny how you can feed your road vehicles on more or less anything from anywhere and very few give a second thought to it.  Indeed there's very little evidence to support the claims of those few who worry about supermarket petrol v named brands IMHO. Used Sainsbury's diesel exclusively in my 160000 mondeo and petrol in our other cars with no issues at all..........loads of Nectar points though! Standard oils in the engines, but careful to check that they conform to manufacturers' specs.

Just look at the huge range of model glow fuels that are available..... all sorts of oils and nitro, magic additives and secret brews........are they all really necessary?

Just saying, no axe to grind. Quite happy with my Laser fuel that runs everything in my fleet.

[Jon H]

You are quite right Cuban. All glow fuel is simply methanol and oil. You dont need nitro, or unicorn tears or whatever else they put in it. Methanol and oil will get the job done. 

 

The synthetic vs castor argument has been settled and castor is dead. Im sorry to upset any castor enthusiasts but that really is the way it is now. The argument of which synth oil is mostly meaningless as well because they are all pretty similar. As long as they have a good heat tolerance (early synth's didnt) then you will be just fine. 

 

Nitro has its advantages. 5% will give a little more power, slightly cooler running, easier starting when cold (like freezing temperatures), and a slightly less critical needle while not incurring penalties like excessive fuel consumption. Above 5% the negative effects of high fuel consumption begin to encroach on the advantages to a point where there is no actual advantage to using it unless you have one of those specific cases discussed before like a helicopter where the cooling aspect is more important than anything else. 

 

In any case, the reason for all these fuels is the simply marketing, trying to get customers over the line, and resistance to change. Model Technics could have discontinued their entire range and simply sold their techpower fuel with varying nitro content. But modellers are a stubborn bunch and trying to convince them to change from duraglo would not have been easy as 'synthetic is bad, my mates merco blew up back in 1978 and im never using synthetic, castor is brilliant, i even add 5% more just to make sure my model is a filthy mess'.  They even had 2 identical fuels with different labels and customers still claimed they could tell the difference. 

 

Another thing to remember is that by selling you a 'better' fuel, they can get away with charging more for it. 

 

Most of the advantages of fancy fuels are, sadly, all in our heads. 

[Don Fry]

Do you believe in Father Christmas, Jon?

[David Davis]

I always thought that OS fourstrokes preferred fuel with 10% nitro in it. Is that not the case Jon? It's what I've always used.

[Jesus Cardin]

6 hours ago, Engine Doctor said:

Just out of interest In what way did it ruin it ?

The piston seized against the cylinder. And it happened so quickly that I simply didn´t have even time to twitch with the needles.

I used the 16% fuel just because I runned out of stock of my normal 10% and went for the 16% so as to being able of making a few flight more, but no way after the seizing!

[Jon H]

38 minutes ago, Jesus Cardin said:

The piston seized against the cylinder. And it happened so quickly that I simply didn´t have even time to twitch with the needles.

I used the 16% fuel just because I runned out of stock of my normal 10% and went for the 16% so as to being able of making a few flight more, but no way after the seizing!

 

this was not caused by high nitro fuel

[Jon H]

1 hour ago, David Davis said:

I always thought that OS fourstrokes preferred fuel with 10% nitro in it. Is that not the case Jon? It's what I've always used.

 

No they are quite happy on 5. i have run all of my OS's on 5% and they work fine. Currently my AWXL uses the OS240 with 5 nitro and 15 oil. Its a thing of beauty. 

 

In the past i ran an OS91 (still got it), my dad has a 52, i had a 52, i currently have that ruined 40 i rebuilt as well. The saito 45 in my nieuport, the enya 53 in my Tomahawk, the enya 155 in my pulse. All 5% nitro and 15% oil. 

 

I also run an ASP160 twin i just remembered. 5% nitro but only 10% oil. 

Edited December 18, 2021 by Jon - Laser Engines

[Engine Doctor]

19 hours ago, Jesus Cardin said:

The piston seized against the cylinder. And it happened so quickly that I simply didn´t have even time to twitch with the needles.

I used the 16% fuel just because I runned out of stock of my normal 10% and went for the 16% so as to being able of making a few flight more, but no way after the seizing!

Hello Jesus. I don't think the fact that your fuel had 16% nitro would have caused it to seize. Its more likely an oil issue or mechanical fault. When temp rises in an engine it can happen very quickly causing mechanical failure. By the time you even notice there is a problem the damage is already done. 

[Engine Doctor]

I ran a Saito 50 for years on a " have a go" trainer at the Padddock Wood show and various other club open days on a 10% nitro 17%  synthetic oil mixed for me by Dave at  Southern Model Craft . I used on many other models apart from my YS powered jobs.  Each have a go session lasted an hour with various members of the public,  mainly children having a go. They gave the models and engines a hard time!   The tank was an 8 oz and lasted about 25 to 30 minutes. That Saito run for many hours each year outliving three models . Only one set of bearing replaced in all that time. Its still flying regularly in a club mates model with original  piston ring and cylinden . In my view 5% or 10% nitro made very little difference to the running but oil and its content did. The noticeable difference came from having a slightly lower oil content giving a better performance and idle and approx 5 min extra running time from a tank. Would I use high nitro in a cooking fourstroke ? NO it would just be a waste of money. I only used the 10% in the Saito to simplify fuel purchase/selection.

[Jesus Cardin]

On 18/12/2021 at 15:54, Jon - Laser Engines said:

 

this was not caused by high nitro fuel

The engine flew every Sunday using 10% nitro Modeltechnics Formula Irvine and Ducted Fan fuels -the latter more than 5 years old- for more than 2 years without a problem nor quitting once on the air. Then the engine sizes a few seconds after switching to Modeltechnics Duraglo 16%.

After repairing the engine (only the piston required some work and polishing!) it has been working faultesly since then, using again the original fuels.

Sincerely I do not know if the problem came from the 6% more nitro, the 3% less lubricant or, most probably, the combiation of both but you may be sure I have lost all interest on trying 16% nitro glow fuel again in any of my 4 stroke engines.....

[J D 8]

         Did you open the needle up some when on the higher nitro fuel ?

[Cuban8]

Love Jon's reply about the crazy plethora of fuels - very amusing and still very relevant given the way that some modellers still hang on to old wives tales etc.

[Nigel R]

I agree.

 

I buy fuel. Every motor I have seems to run just fine on it, and none have come to grief or gone prematurely rusty. All synth and 5% nitro in my case.

[Jon H]

i think this myth about high nitro fuel being better (especially for 4 strokes) comes from the fact that many people never touch their slow run needles. 

 

I have gone over this before, but manufacturers like os and saito ship their engines with slow run needles set quite rich. Why? because they do not test run them a rich slow run almost guarantees the engine will at least start. If the engine is set 'correctly' without running the engine there is a chance it will be a shade lean for that specific engine and the engine will not start. This causes problems as many people really struggle with diagnosis of an engine that will not fire up at all. 

 

So you fire up your new beast on 5% fuel and it idles badly, shakes about, stops etc. This happens until the club expert tells you to use 10% nitro and hey presto! much better. So you conclude that high nitro is better and the myth continues. The reality is that high nitro fuel needs a richer mix than lower nitro and the change to 10% fuel often brings the engine into tune with the formerly rich slow run tuning it shipped with. For the sake of maybe 2 minutes with a small screw driver the slow run needle could be adjusted to suit the 5% fuel you started with and the engine would perform just fine. 

 

The other one is my personal crusade, tank placement. High nitro fuel will to some degree allow a little more tolerance if the tank placement is poor. 

 

So for the small amount of effort needed to get the tank placement right and tune up your slow run needle you can ditch the expensive and thirsty 10+% fuel and drop to 5. It will save you money, make the model cleaner, give longer flight times, and you can be all smug when your engine just keeps going and going ?

[Jon H]

13 hours ago, Jesus Cardin said:

The engine flew every Sunday using 10% nitro Modeltechnics Formula Irvine and Ducted Fan fuels -the latter more than 5 years old- for more than 2 years without a problem nor quitting once on the air. Then the engine sizes a few seconds after switching to Modeltechnics Duraglo 16%.

After repairing the engine (only the piston required some work and polishing!) it has been working faultesly since then, using again the original fuels.

Sincerely I do not know if the problem came from the 6% more nitro, the 3% less lubricant or, most probably, the combiation of both but you may be sure I have lost all interest on trying 16% nitro glow fuel again in any of my 4 stroke engines.....

 

The OS 40 uses an ali piston, iron ring and electroless nickel plated liner if i recall correctly. For the aluminium piston skirt to pick up on the cylinder wall is, to say the least, unusual. For ali to pickup like that it must have been a lubrication issue but this would have damaged the liner as well. I saw this on a laser 240 some years back when the owner decided to mix his own fuel and i think used beef dripping or similar as an oil. Whatever he used it didnt lubricate the engine at all and the pistons were bone dry when i stripped the engine down. 

 

For the engine to have actually seized the liner must have also been damaged, and even so there is no way the fuel was to blame. 

 

Do you have any photos of the damage?

 

[Nigel R]

8 minutes ago, Jon - Laser Engines said:

make the model cleaner

 

Yup, I find only a smear of oil from 4 strokes on full synth.

 

I concede my two strokes are still messy, slimy animals, regardless of fuel.

[Nigel R]

7 minutes ago, Jon - Laser Engines said:

beef dripping

 

Makes the best chips.

[Paul De Tourtoulon]

Were have been hit by the idiots ( can I still say that ? ) in Brussels, we can't but any fuel over 16% nitro over the counter unless we have

 a model competition licence as nitro has now been deemed as an explosive !?

[Jon H]

5 hours ago, Paul De Tourtoulon said:

Were have been hit by the idiots ( can I still say that ? ) in Brussels, we can't but any fuel over 16% nitro over the counter unless we have

 a model competition licence as nitro has now been deemed as an explosive !?

 

As you only need 5% for most applications who cares? 16% is enough for a nitro car or a heli....unless you are mega competitive, but then if everyone else is limited to 16% as well its still a level playing field. 

[Don Fry]

In fairness to the idiots, converting nitromethane to a very decent explosive is not difficult. Keeping alive and intact in the process requires planning. So on two counts, it should be discouraged. 

[Paul De Tourtoulon]

I fly 3D with my Raptor .50 with it's OS 50 Hyper, try that with 10% nitro ?it needs at least 20% to perform properly,

all my other  stuff  runs with  7.5 % / 10% nitro,

 

 And for you Don, there are 1.000 easier ways,,,,

[Martin McIntosh]

I normally use MT Yamada mix 20% nitro on my YS motors but they would be quite happy on less. They do, however, require 23% oil but this is easily added. Regarding the OS, if it is an early motor then they do state a minimum of 18% oil. Some of that MT stuff (Duraglow, Dynaglow?) has considerably less.

A fuel change from 10 to 16% would certainly require richening all round but maybe not so easy to detect on a four stroke.

[Jon H]

Do they actually need 23% oil? that seems crazy and they have even put it up as 20/20 used to be the favoured ys fuel state side for years. Just seems weird they need that much slop. I wonder if its for sealing all those supercharger bits ? 

 

On the older OS engines they do recommend 20% castor but i just run 15% synth. My 240, 15fp etc all recommended the 20 castor and it just not needed. I fact i think the 240 could run down to 10 easily as its a bit messy even on 15 and my ASP160 twin runs on 11% without issue. I leave it though for the simple reason that it works just fine as it is and 10% oil would be yet another fuel. 15% and 7% oil are the only 2 fuels i will bother with once my one bottle of 11% runs dry.