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Author Topic: Needle Settings on Different Fuels  (Read 1730 times)

Online Motorman

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Needle Settings on Different Fuels
« on: October 08, 2014, 08:49:41 PM »
Was flying (racing) a Fox 35 today on 5/28 switched to 10/20 and thought I'd have to go richer for the higher nitro but I had to go leaner. Can't figure it. the 10/20 was a week old and the 5/28 was mixed today. Does nitro lose it's punch that fast?


MM
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Offline RknRusty

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Re: Needle Settings on Different Fuels
« Reply #1 on: October 08, 2014, 09:27:31 PM »
Quote from: Motorman on October 08, 2014, 08:49:41 PM
Was flying (racing) a Fox 35 today on 5/28 switched to 10/20 and thought I'd have to go richer for the higher nitro but I had to go leaner. Can't figure it. the 10/20 was a week old and the 5/28 was mixed today. Does nitro lose it's punch that fast?


MM
It should not lose its punch if sealed tightly. I would have guessed the same thing as you, unless the temperature rose and/or barometric pressure dropped drastically in between your fuel change. It would take a helluva shift in weather to be that obvious. I think I'm looking at that right.
Rusty
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Offline Tim Wescott

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Re: Needle Settings on Different Fuels
« Reply #2 on: October 08, 2014, 09:43:05 PM »
Less oil means less viscosity, particularly if the 20% oil fuel has a lot of synthetic.  So you may have been flowing more fuel, even with the leaner setting.
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Offline Ron Cribbs

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Re: Needle Settings on Different Fuels
« Reply #3 on: October 08, 2014, 10:35:18 PM »
Tim is right and I bet it flew a little faster too. Oil robs a little power, I am one of those jokers who uses 10/22 in Foxes. 20% is low though even I am not that brave!





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Online Brett Buck

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Re: Needle Settings on Different Fuels
« Reply #4 on: October 08, 2014, 10:39:01 PM »
Quote from: Motorman on October 08, 2014, 08:49:41 PM
Was flying (racing) a Fox 35 today on 5/28 switched to 10/20 and thought I'd have to go richer for the higher nitro but I had to go leaner. Can't figure it. the 10/20 was a week old and the 5/28 was mixed today. Does nitro lose it's punch that fast?

   Tim has it. And you didn't set it leaner - you had to screw the needle in, but it was flowing MUCH more fuel, so it was much richer to start with, and then you had to screw it in just to get the same mixture - so it wound up about the same.

    Brett
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Online Motorman

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Re: Needle Settings on Different Fuels
« Reply #5 on: October 09, 2014, 08:02:23 AM »
Never thought about viscosity, makes sense, I was thinking there was more alky in the 10/20.

That's the problem with racing the Fox 35, you're destroying the motor. The allowed fuel 10/20 gives the most power but, they should switch to Fox Superfuel 5/28 for less heat more lube.

Also, with a wider needle setting tiny dirt particles that would clog the system can get through.


MM
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Offline C.T. Schaefer

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Re: Needle Settings on Different Fuels
« Reply #6 on: October 11, 2014, 06:59:42 PM »
Walt, Just so you know. The fuel for our meets must contain no more than 10% nitro. The rest is up to you. Gentlemen's rules. At Brodak you have your choice of  blends supplied by JB. 20% or 29% oil.   TS
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