Need Help with Fuel Composition

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Need Help with Fuel Composition

Postby Bruce8 » Wed Jan 02, 2013 11:49 am

Hello everyone!
I am about to order an ASP S21A engine for an aircraft that I am about to build. I would like some help regarding fuel composition because I heard that I could run this glow engine WITHOUT nitro. Is this
a) good for the engine? Running without nitro lowers the cost of the fuel significantly and nitro is not always available. Does it make a mess?
b) If I can run it without nitro, what should the ratio of methanol to oil be?
c) If I should run with nitro what should the ratio of methanol, oil and nitro be?
d) What brand of oil can I use?
e) Any specific type of methanol?

Thanks would love to hear all views! :)
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Re: Need Help with Fuel Composition

Postby iflylilplanes » Wed Jan 02, 2013 3:12 pm

I have been running glow engines without nitro for 40 years, both 2 and 4 stroke. Any motor that had trouble running I just added an on board battery that heated the plug at idle. The running of fuel with nitro added will make the engine more powerful depending on the % of nitro, if you want to run nitro 5% seems to be the best for flying, it keeps the plug alight at idle.
The one draw back with nitro fuels is that the burning of nitro has a byproduct of nitric acid, this can cause corrosion inside the motor unless you put an after run oil in the motor at the end of the days flying. By the way the term nitro engine was coined by the car and boat guys over the last 5 or 6 years, the 2 dimensional RC hobbies (cars and boats) used nitro fuels to get the speed up. Us, of the 3 dimensional, more skillful hobby of RC flight are getting 300K out of Formula 1 pylon racers on standard 4 to 1 fuel without nitro, speeds that cars and boats still could not get on 100% nitro.
The best glow fuel is 20% castor oil to 80% methanol, when running in a new engine you can go up to 25% castor oil 75% methanol.
Castrol sell castor oil here in Australia, and Shell A racing fuel is an Ok methanol, it has a perfume, flavor and color added but works well, if you can get pure methanol without the additives that works as well.
Many Thanks,

Dave W.


Dead Stick Glide Distance: Half the distance from the airplane to the nearest emergency landing field.
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Re: Need Help with Fuel Composition

Postby BillGriffiths100 » Wed Jan 02, 2013 4:03 pm

As a rule of thumb the bigger the engine the better it runs on non-nitro fuel, the 21 is a small high revving engine and it probably won't run very well on less than 5% nitro.
ALTHOUGH I still have an enya 19 that would run faultlessly on non-nitro in all weathers!
In a warmer climate non-nitro fuel also works better, so the only way to see is to try it buy some straight and 5%
and compare.
Quite often in my impoverished days I would mix 5% and straight and get the engines to run well on 2 1/2 %
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Re: Need Help with Fuel Composition

Postby iflylilplanes » Wed Jan 02, 2013 11:50 pm

I agree with Bill, I have used 5% in some of the Cox engines I own, they can be a little cantankerous. My first glow motor was a Super Tigre Q20/15, never had nitro, I would have 20 x 6 minute flights on a Sunday (small tank), this motor never missed a beat, it would idle so slow all I had to do to stop it was press a finger in the centre of the spinner and at full throttle this 2.5cc motor would just keep going never loosing power. On the other hand 21 size engines are known as high revving and a little hard to get going, so 5% would help if your motor is being a little difficult, also if like Bill you are from a colder climate nitro will help, but also the right glow plug can make a difference as well.
Many Thanks,

Dave W.


Dead Stick Glide Distance: Half the distance from the airplane to the nearest emergency landing field.
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Re: Need Help with Fuel Composition

Postby Bruce8 » Thu Jan 03, 2013 12:01 pm

Wow,
Thanks for all the replies guys! I live in India so I doubt the cold climate will be a factor because it never dips below 20 degrees Celsius!! I will take your advice on both the ratio of 20% to 80% castor to methanol respectively and on the Castrol and Shell A racing fuel. Could you give me any alternatives to the Shell? Does Shell or any other brand sell methanol? I fear that the shell a racing fuel will be expensive :( and not always available. What source of methanol do you guys use?
Thanks once again
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Re: Need Help with Fuel Composition

Postby BillGriffiths100 » Thu Jan 03, 2013 3:40 pm

You'll probably have no problem getting methanol in India.
I've just discovered that I can buy a 25 litre drum for £45

Bruce has an article on this website about sourcing oil here it is:
http://www.rcmodelreviews.com/goodoil.shtm
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