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OS Engine & fuel


Paul Law
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I have an OS 46AX 11 engine in my Irvine tutor, before i run the engine, what type of fuel would you recommend ? Would i be safe enough running the same fuel (Cool power 10%) on the Tutor as i do in my heli's ? Cool power appears to be a lot harder to get these days, may be more prudent going for a fuel more easily found ?

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There's not much difference between Contest 10 and Bekra 10 - I think the biggest difference is the use of either Klotz Techniplate or Super-techniplate. I know that the Bekra is pure synthetic - no castor at all - as castor causes a lot of varnishing / silencer clogging on helis.

In days of yore there was quite a lot of prejudice against pure synthetic oils in fuel, but I've run Bekra for years in the most demanding of circumstances without any issues.

--

Pete

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I think the most important thing is keep the fuel fresh by storing it carefully. Keep it free of debris , be clean when filling the tank and run the engine on the very slightly rich side. Doing that with any fuel should keep the engine happy what ever the makeyes

Saying that I use Prosynth 5% on everything!

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  • 7 years later...
On 05/08/2014 at 20:35, Jon Laughton said:

Most of my ic engines are OS: I used to use Model Techincs Duraglow 10% but after a few inexplicable deadsticks I was advised to change to Westons Prosynth 2000 10% and it was a great call.....

In the early days, the 1980s, I used nothing else only Duraglow by Model Technics.   But for the last 10 years, all I use in both two strokes and fourstrokes is Optifuel 12.  This fuel runs all my engines without any hint of trouble.  

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Not much choice here in France, only 3 makes to choose from, whatever they are I put 2° caster in them and the rest synthetic oil to bring it up to 17% oil, and 10% nitro, I run all of my stuff on it, from my HP.21 vt / Saito 120  four strokes to my  two strokes, Irvin,  Os and up to my .90 rossi  not forgetting my helicopters OS .50 hyper and  Novarossi .61,,,

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1 hour ago, John Stainforth said:

I'm another fan of Optifuel 12. Frank, have you tried your OS55AX on  10, 12 or 15% nitro?

 

No, I have a stock of straight synthetic and it runs really well on that and is perfectly powered for my Astro Hog, so don't need to go to the expense. It's only been flying for 3 years in this plane which is probably about 120 hours running. The AX series are really good engines.

 

 

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10 minutes ago, Frank Skilbeck said:

 

No, I have a stock of straight synthetic and it runs really well on that and is perfectly powered for my Astro Hog, so don't need to go to the expense. It's only been flying for 3 years in this plane which is probably about 120 hours running. The AX series are really good engines.

 

 

I have two 55ax engines and they run very nicely.  

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10 hours ago, Frank Skilbeck said:

I run my OS55AX on Southern Model Crafts 0%, runs really well.

Years ago at my club, we all used Straight Fuel for everything. The motor gerus warned us of using nitro added fuel as it " rots your motors " they claimed.

Times have changed, and we all run motors dry etc, at the end of the day, but all motors will run on Straight Fuel.

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More nitro will mean more rust to be fair, especially in a 2 stroke. 

 

Given the cost, rust, mess, and fuel consumption disadvantages of high nitro fuel i wouldnt recommend more than 5% for anything to be honest. YS are another story, and heli's use the fuel as coolant so that too is different, but for general sport/scale/aerobatic flying it will make no meaningful difference to the performance of the engine once tuned to suit it. 

 

 

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13 hours ago, Denis Watkins said:

Years ago at my club, we all used Straight Fuel for everything. The motor gerus warned us of using nitro added fuel as it " rots your motors " they claimed.

Times have changed, and we all run motors dry etc, at the end of the day, but all motors will run on Straight Fuel.

That's not the reason I do it, it's more to show the guys who insist you need 10% nitro to get a good starting, idle and pick up, my OS55AX when properly primed starts very easy with a back flick, takes a few flicks at the start of the day but then usually one or two on subsequent flights. I have recently started adding 25% neat methanol to reduce the oil content a bit, so far the engine continues to start and run really well, but I haven't really seen any less goo on the model 😄

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Nitromethane does provide a noticeable power boost but needs much less air to burn than methanol, increasing the rate of fuel consumption for the fuel mix and I suspect that the “easier handling” claims have much to do with the increased volume of fuel being metered by the crude carburettors we use, making adjustments a little less critical. 

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