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OS 4 stroke 20% nitro.


Mike Watters
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2 hours ago, Jon - Laser Engines said:

 

Saito do have a much higher nitro tolerance than OS. Their combustion chamber design, compression ratio etc are different to the OS so i would recommend against direct comparisons of this nature. The OS 40fs can be a little vicious with a desire to throw props if you upset it. As mentioned before, Enya engines did the same and they provided a head shim for use with high nitro to prevent props making a bid for freedom. 

 

This is another reason i always just recommend 5% None of this faff or worry about things falling over. 

 

My Saito 45 and 45 specials run fine on 5/15 nitro/oil despite the instructions telling me i must not use full synthetic fuel and up to 30% nitro. 

Hi Jon, I just have the two OS fourstrokes, a 95v and a nib surpass 52.  The rest are Saito .  I run all on Optifuel 12.  Will the two OS engines in your opinion then run better on Optifuel 5 ?  

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4 minutes ago, aidan mcatamney said:

Hi Jon, I just have the two OS fourstrokes, a 95v and a nib surpass 52.  The rest are Saito .  I run all on Optifuel 12.  Will the two OS engines in your opinion then run better on Optifuel 5 ?  

 

Better? no. The same? yea pretty much. 

 

Pro's and con's opti 12 with 18% oil vs a 5% nitro 15% oil fuel (like the new laser 5 coming from opti). 

 

Pro's:

 

Cheaper fuel
Less mess/oil residue
Better fuel economy

Slightly more sensitive needle so its easier to find optimum tuning

Engine will run a tiny bit hotter which is good for the plug and preventing rust in the crankcase

Slightly decreased chance of rust inside the engine. 

 

Con's

 

Slight loss of power 

Slightly more sensitive needle so tuning errors are more apparent. 

Engine will run slightly hotter so poor cooling in a cowl is more likely to be exposed. 

 

This video is of the OS FF240 i have mentioned which is in my AWXL. It runs 5/15 as i have said before. Its 4 cylinder, single carb and yet on 5% nitro with no glow support it is completely reliable, easy to start and generally a delight to use. Its a bit messy and i would never use more than 15% oil because of that, but its not as bad as might be expected for a 40cc glow engine. My OS91 surpass also flew for years on 5/15 and although currently in storage it will run on it again should i put in back in another model. 

 


 

I think the question of 'is X or Y better than Z' leads many modellers to buy stuff they simply do not need and do not get any benefit from. Servo's with 10kg torque in a wot 4 would be an example. Are the 10kg digital ones better? sure, but do they actually make the model better than if you had used standard servos?..no probably not. At least not to the point where the improved performance outweighs the cost (financially in this case) of the 'better' equipment. 

 

Nitro is the same sort of deal. Yes it has advantages to some people in specific applications (helicopters, cars, boats, flying up a mountain). But, there are downsides and unless your engine is tuned mechanically to take advantage of it (YS for example) and you yourself have tuned the engine for peak performance to exploit the added performance, there will be little to no meaningful advantage and only disadvantages of cost, mess on the model and high fuel consumption. Will you blow up most engines using 15 or even 20% nitro? no probably not, but its very unlikely to offer a tangible improvement in your enjoyment of a given model. For probably 90% of models 5 nitro 15 oil is more than sufficient so save your pennies ?

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1 hour ago, Jon - Laser Engines said:

 

Better? no. The same? yea pretty much. 

 

Pro's and con's opti 12 with 18% oil vs a 5% nitro 15% oil fuel (like the new laser 5 coming from opti). 

 

Pro's:

 

Cheaper fuel
Less mess/oil residue
Better fuel economy

Slightly more sensitive needle so its easier to find optimum tuning

Engine will run a tiny bit hotter which is good for the plug and preventing rust in the crankcase

Slightly decreased chance of rust inside the engine. 

 

Con's

 

Slight loss of power 

Slightly more sensitive needle so tuning errors are more apparent. 

Engine will run slightly hotter so poor cooling in a cowl is more likely to be exposed. 

 

This video is of the OS FF240 i have mentioned which is in my AWXL. It runs 5/15 as i have said before. Its 4 cylinder, single carb and yet on 5% nitro with no glow support it is completely reliable, easy to start and generally a delight to use. Its a bit messy and i would never use more than 15% oil because of that, but its not as bad as might be expected for a 40cc glow engine. My OS91 surpass also flew for years on 5/15 and although currently in storage it will run on it again should i put in back in another model. 

 


 

I think the question of 'is X or Y better than Z' leads many modellers to buy stuff they simply do not need and do not get any benefit from. Servo's with 10kg torque in a wot 4 would be an example. Are the 10kg digital ones better? sure, but do they actually make the model better than if you had used standard servos?..no probably not. At least not to the point where the improved performance outweighs the cost (financially in this case) of the 'better' equipment. 

 

Nitro is the same sort of deal. Yes it has advantages to some people in specific applications (helicopters, cars, boats, flying up a mountain). But, there are downsides and unless your engine is tuned mechanically to take advantage of it (YS for example) and you yourself have tuned the engine for peak performance to exploit the added performance, there will be little to no meaningful advantage and only disadvantages of cost, mess on the model and high fuel consumption. Will you blow up most engines using 15 or even 20% nitro? no probably not, but its very unlikely to offer a tangible improvement in your enjoyment of a given model. For probably 90% of models 5 nitro 15 oil is more than sufficient so save your pennies ?

Thats great information Jon, many thanks.  So helpful.  Will try the Laser 5 on my OS 95v in the new year .   I'm also hoping to buy a Laser engine for the first time in the new year also , either a 70 or an 80,  will be in touch with you about that at some stage.   

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I always recommend the top of the tank in line with the centre of the needle. You can get away with it a little higher, but i always shoot for that where possible as it gives a fall back position if you cant get the tank lower without it falling out of the model. 

 

The inverted saito 45 in my Nieuport has always been completely reliable and even without an exhaust its quieter than some of the electric models at my club. It will fly about half an hour on what i think is a 6oz tank...not sure, i dont remember and i normally only fly about 10-15 mins anyway. 

 

 

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Sounds good. I had a saito 62 for a short time. Came in a model i bought 2nd hand and it ran nicely on the 5/15 mix. I bench ran it to make sure it was ok before selling it as it was surplus to my requirements, but it purred along like a larger version of my saito 45 special and i did toy with keeping it for a 1/6 BUSA Pup i have. But i decided to sell it as i have 3 spare saito 45's, at the time a spare enya 53, a laser 45 and 50 so i have no shortage of options! Most likely it will end up with a 45 special as the old laser's are physically too large to go in there nicely. 

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  • 2 weeks later...
7 minutes ago, Bruce Collinson said:

Jon,

 

I thought there was a persuasive reason not to try Laser-Lite/7% oil in OS or Saito?   Certainly seems to me to put them out of warranty.

 

Did I miss something?

 

The amount of waste oil ejected by my Saitos on 15% oil makes it very tempting, but ....

 

BTC

 

Give it a go if you like. The worst that will happen is the conrod will seize on the big end and then snap. Admittedly that is pretty bad, but still!

 

The problem is not all saito engines are created equal. Older ones had bronze big end bushes and they stand a better chance on low oil than the ones that run straight on the plain ali rod. One customer has decided to feed the 7% oil fuel to his OS 120 4fs and it seems to enjoy it. 

 

OS engines are well made and would probably be fine. Enya as well would likely be ok. The problem is i dont know for sure and i will not recommend 7% oil for those engines. 15% oil is fine in everything though. 

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