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RE: Which Fuel to use? - 4/2/2006 2:06:48 AM   
loughbd


 

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Status: offline 		Yup that's what we see. $$$$$ as in burned up engines from lack of oil.

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RE: Which Fuel to use? - 4/14/2006 3:40:34 AM   
freshane


 

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Joined: 3/23/2006
From: CR, BC, CANADA
Status: offline 		hi My LHS actually has this XP Car XTREME Fuel 20% and 30% for a really good price. I have a RS4 type SS and just wanted to know what % would be best. He was saying that 30% more power and runs cooler. But I thought that going higher meant shorter engine life. And if anyone has used this fuel can you give me some feedback on it. They don't carry Odonnels and Traxxas top fuel is so overpriced here its like 44 bux! Thanks

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RE: Which Fuel to use? - 4/14/2006 3:51:23 AM   
Dawman



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From: Marseilles, IL, USA
Status: offline 		I would just run 20% . I only run 30% in my engines that have been extremely modded . But you will hear different sides from people .

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RE: Which Fuel to use? - 4/14/2006 4:08:24 AM   
livindead


 

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From: des moines, IA, USA
Status: offline 		i think that the really important thing is that no matter what fuel you chose stay with it...i run byrons 20% and thats all ...not to say you cant experiment between brands but if you break in with 20% nitro then goto 30 you have basicly just resized your sleeve for 30% and you wont have the compression you had if you go back to 20%...

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RE: Which Fuel to use? - 4/14/2006 4:57:30 AM   
loughbd


 

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Status: offline 		Nitromethane is an OXIDIZER and generates heat. Heat is power and that's why we use it. It does not make an engine run cooler.

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RE: [Awaiting Approval] - 4/14/2006 2:56:58 PM   
Dawman



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Status: offline 		not true , in a few cases I`ve had to use my 30 % when I was out of 20% and have gone back to 20% . It does not resize the sleeve nor loose compression . That is just some story that was made up . I have experimented with different fuels and % in the past 5 years and there are no facts that it happens .

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RE: [Awaiting Approval] - 4/15/2006 4:33:01 AM   
downunder



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quote:

ORIGINAL: Dawman
It does not resize the sleeve nor loose compression . That is just some story that was made up.

Correct. This is just another of the urban myths about ABx type engines based on the idea that high nitro makes them run hotter where in fact sometimes they'll actually run cooler. But the differences in temperature (hotter or cooler) is very small and less than you'll have between running them in summer/winter or full/part throttle. But if you go from 20% to 30% and don't retune then you'll have a much hotter engine because the mixture will be too lean.

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RE: [Awaiting Approval] - 4/15/2006 4:40:02 AM   
loughbd


 

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Status: offline 		Urban myth???? Nitromethane DOES make an engine run hotter. That's why we use it. Heat is power and that's where the power increase comes from when you use nitro methane. That's also why little engines like the Cox 049's need high nitro content fuel. They are very small and give off there heat very quickly. The high nitro content of Cox fuel 25 to 35% nitro is what keeps these little guys hot so they run well.

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RE: [Awaiting Approval] - 4/15/2006 5:05:58 AM   
Dawman



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Status: offline 		well ya . Maybe thats why they think it resizes the sleeve . They don`t retune and end up wearing the sleeve out .

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RE: [Awaiting Approval] - 4/15/2006 6:38:09 AM   
loughbd


 

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Status: offline 		It's not an urban myth nitro methane is an oxidizer and it makes an engine run hotter. That's why we use the stuff. heat is power and we use nitro because it generates heat which increases power. Also, running and ABC engine hotter DOES cause the cylinder to expand more. That's why all the manufacturers as well as the engine columnists like Clarence Lee, Joe Wagner, Dave Gierke, George Aldrich etc tell you to break an ABC in on the fuel you are going to use. That's also why as an ABC slowly wears you can use less nitro. The engine runs cooler and the cylinder expands less and compression is regained.

Get yourself a copy of the R/C Engine Volume III by Clarence Lee or the 2 Stoke Glow Engine by Dave Gierke and see what the guys who know what they are talking about have to say about the subject. The first is from the RCM anthology and the second from Model Airplane News.

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RE: [Awaiting Approval] - 4/15/2006 2:43:52 PM   
Dawman



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From: Marseilles, IL, USA
Status: offline 		I don`t need a book . I have my own test results and facts .

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RE: [Awaiting Approval] - 4/15/2006 3:09:56 PM   
downunder



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Status: offline 		Those who get all their knowledge from books and magazines will never try anything themselves. It's surprising how wrong the books can be sometimes.

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RE: Which Fuel to use? - 4/15/2006 9:08:46 PM   
Sport_Pilot



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quote:

ORIGINAL: loughbd

Nitromethane is an OXIDIZER and generates heat. Heat is power and that's why we use it. It does not make an engine run cooler.

.
Nitro is a monopropellent, that means it will burn without additional air. That is why pure 100% nitro will run stronger and stronger the richer you run it. It would indeed run hotter if you ran a perfect stochastic mixture, but since nitro runs faster extra rich it will run cooler. Heat is basicly the transfer of temperature by conductance or mass. So more mass flow even at a lower temperature can be more heat and power.

So our engines will run either hotter or cooler with more nitro. Depends on various varibles. If compression is adjusted for ideal then the temperature would go up from a low to medium nitro fuel, then it would drop when to below the low nitro when the nitro is rasied further. This is due to the interaction of methanol, nitro, and oil and how they act at richer mixtures.

Be carefull even if the engine is running cooler on higer nitro, a lean run means it will run hotter than a lean run on low nitro.

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