Notices
Questions and Answers If you have general RC questions or answers discuss it here.

5% or 10%

Old 08-29-2008, 06:53 AM
  #1  
berrs003
Junior Member
Thread Starter
 
Join Date: May 2006
Location: KentKEnt, UNITED KINGDOM
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
Default 5% or 10%

Can somebody simply explain the differnece. i have an irvine 46 and currently run a 12x4 on 5%?

What advantages does 10% or even 15% bring?
Old 08-29-2008, 07:30 AM
  #2  
kid chuckles
Senior Member
 
Join Date: May 2007
Location: cando, MO
Posts: 926
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

just more nitro content. More nitro more power but not really enough to notice. Between 5-15%
Old 08-29-2008, 08:14 AM
  #3  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%


ORIGINAL: berrs003

Can somebody simply explain the differnece. i have an irvine 46 and currently run a 12x4 on 5%?

What advantages does 10% or even 15% bring?

Unless you are competing in something with more than one airplane in the air at a time, won't ben any advantage at all. Changing to a fuel that is only 5% difference won't do anything that most modelers could hope to notice.

What you will see is an increased fuel cost. THAT you will notice clearly.

There actually will be a slight increase in engine rpm, but it won't be worth the cost. There also will be a slight decrease in flight times. But it won't usually be enough to matter. The might be either a slight increase in engine heat. And there could even be a slight decrease in engine heat. Neither will do anything worthwhile for you, if they actually happen. You probably will have to adjust your needle valve. About a click. Maybe two, depending on the engine. But changes in weather usually have more effect on needle than a 5% change in nitro.

What advantages would changing your fuel from 5% to 15%? Are you racing? Are you flying pattern and are under-engined? If you aren't doing either, there really aren't any advantages. If you are 3D'ing the model, and with that prop you might be, and the 3D is suffering from a power problem, you need to retrofit something like an OS55AX. The difference in lugging power that 10% nitro might give you probably won't make a good plane out of an underpowered one. Yeah, you should see a bit more pulling power, but the chances aren't good that it'd be enough.

The beauty of our hobby is that we can try stuff and not risk much. Heck, try some 15% and see if you get what you are looking for. Borrow some from another modeler or buy a quart.
Old 08-29-2008, 08:22 AM
  #4  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

You know, I messed around with an OS70FL 4stroke for awhile. It was a real problem. My first 4stroke and it had problems. I had problems too. So I got the 4stroke guys at the field to mess with it. It still ran like crap, so they did all the things they said should be done with 4strokes. One was to run at least 15% nitro in the sucker. It actually ran a bit better. Actually, it still ran like crap, but it did start a bit easier. So there just might be some reason to use 15%.

The experts at my field all seemed to feel that 4strokes run better with more than 10% nitro. So nitro does mean something sometimes. To some people.
Old 08-29-2008, 09:18 PM
  #5  
Gray Beard
My Feedback: (-1)
 
Join Date: Apr 2003
Location: Hemderson, NV
Posts: 14,385
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 5% or 10%

About all you will see between your 5% and A change to 15% is A lighter wallet and an engine that may or may not be easier to tune. In glow engines I operater two strokes from .25 to .91 and then I start getting into my four strokes from .91 to 1.40. I burn 15% in everything. Just because I don't want to have to keep A lot of different blends around. My four strokes run fine on 10% but the more nitro the easier it is to get the low end in tune. The higher the nitro I use the easier it is to find that sweet spot but the extra price I have to pay after 15% just isn't worth it to me, I took the time and learned to tune one. There are reasons to run the higher nitro but unless you live in A place like Denver where there is no air then A sport pilot just needs to get what works for him.
Old 08-29-2008, 09:40 PM
  #6  
Jetdesign
Senior Member
My Feedback: (8)
 
Jetdesign's Avatar
 
Join Date: May 2008
Location: Mason, OH
Posts: 7,054
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

I'm in my first year flying and have burned about 12 gallons of fuel this summer. I run a 46AX and a 120AX (both 2 stroke). My experience has been that the 15% nitro burns hotter (engine head is noticeably hotter upon return) and requires a richer setting, which means it uses more fuel. The difference in power is not as noticeable as the fuel consumption. I now use only 10% in my engines.
Old 08-29-2008, 10:41 PM
  #7  
JohnW
Senior Member
My Feedback: (6)
 
JohnW's Avatar
 
Join Date: Mar 2002
Location: Lincoln, NE
Posts: 1,815
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

The power diff may not seem as noticeable as the cost or fuel draw, but we need to keep in mind that power is not a liner function. A 10% increase in power doesn’t increase your RPM much, it will be much less than a 10% increase in RPM. But the 10% increse in power can be felt in the air with certain maneuvers. For the typical flyer I understand this small gain is no big deal and not worth the cost, but I just wanted to point out the gain is indeed there and for certain flying it is important.
Old 08-30-2008, 05:40 AM
  #8  
bbbair
 
Join Date: Jan 2003
Location: Sarnia, ON, CANADA
Posts: 966
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

Everybody here is correct.

Another point to know is that there are some fantastic AC that work on 0% nitro. The guys in Europe have engines designed for 0% and if you enter into International competitions (FAI events) that is the standard.

Nitro Methane is an Additive to increase the RPM and to those people that are competing in things every RPM is important, then the Engineers designed their engines to use Nitro. When the Sport modeller came into being - we just adapted to what was around and here we are.

At the end of the day - for a sport flier - the difference between 10 & 15% is minor.

Enjoy.
Old 08-30-2008, 11:16 PM
  #9  
Charlie P.
 
Charlie P.'s Avatar
 
Join Date: Feb 2003
Location: Port Crane, NY
Posts: 5,088
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%


ORIGINAL: gaRCfield

I'm in my first year flying and have burned about 12 gallons of fuel this summer. I run a 46AX and a 120AX (both 2 stroke). My experience has been that the 15% nitro burns hotter (engine head is noticeably hotter upon return) and requires a richer setting, which means it uses more fuel. The difference in power is not as noticeable as the fuel consumption. I now use only 10% in my engines.
I've tried 5%, 10% and 15% and, until a few years ago, I ran 15% in all my glow. I've come down to 10% now that it's a $5/gallon savings and, though I lose a couple hundred RPM I find it about as easy to tune and set. It does seem the 15% is a little more tolerant of a lean run (as in keeping running) but once the high & low idles are reset it's not much of an issue. My OS 70II is a little less happy with the 10% but the glow engines seem to hardly notice.
Old 08-30-2008, 11:48 PM
  #10  
ChuckW
Senior Member
 
ChuckW's Avatar
 
Join Date: Jun 2006
Location: Clovis, CA
Posts: 5,165
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%


ORIGINAL: da Rock

You know, I messed around with an OS70FL 4stroke for awhile. It was a real problem. My first 4stroke and it had problems. I had problems too. So I got the 4stroke guys at the field to mess with it. It still ran like crap, so they did all the things they said should be done with 4strokes. One was to run at least 15% nitro in the sucker. It actually ran a bit better. Actually, it still ran like crap, but it did start a bit easier. So there just might be some reason to use 15%.
I was running 10% in an OS .91 4-stroke since I had a couple cases on hand. The engine ran fine on 10%, idled well and all but nothing spectacular. I filled it up with Cool Power 15% this morning though and re-adjusted the carb. It was like I had a whole new airplane. The relatively small increase in RPM made a noticeable difference in the air.

For a typical 2-stroke though I figure whatever runs well and is readily available is just fine whether that's 5% or 10%.
Old 08-31-2008, 09:15 AM
  #11  
KW_Counter
Senior Member
 
Join Date: Feb 2003
Location: Lake County, CA
Posts: 1,555
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

When I lived below sea level I used 10% in my two strokes.
Now I live above 2,500 feet and those same engines require 15%.
Use what they run on unless you have some special requirements.
Good Luck,
KW_Counter
Old 08-31-2008, 05:24 PM
  #12  
Gringo Flyer
Senior Member
My Feedback: (18)
 
Gringo Flyer's Avatar
 
Join Date: Jan 2004
Location: Formosa, ARGENTINA
Posts: 2,370
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%


ORIGINAL: gaRCfield
My experience has been that the 15% nitro burns hotter (engine head is noticeably hotter upon return) and requires a richer setting, which means it uses more fuel.
I am not an engine pro by any means but I think an engine runs cooler with higher nitro.

I run 5% all around and am about to try 0% because there is a big price difference in the 2 here.

I run 4 strokes almost exclusively and I get great idle with 5%. I think if you tune well you can get low idle on low nitro. I think higher nitro maybe helps some engines on idle because they arent dialed in right.
Old 08-31-2008, 07:21 PM
  #13  
JohnBuckner
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,441
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

Gringo Flyer, what elevation do you fly at?
Old 08-31-2008, 08:18 PM
  #14  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

Higher nitro actually should make engines run cooler. Nitro has less BTU compared to methanol, which is what it replaces. There's less energy, but lot's more oxygen. Which is why you have to open up the needle valve when you increase the nitro percentage.

Only problem with the engine running cooler with more nitro percentage is often the result of why people used to go to higher nitro. They wanted more rpm. You crank 'em faster, you get more heat in the same time span.
Old 08-31-2008, 08:26 PM
  #15  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

Very often the same change will work one way for some people and an entirely opposite way for other people.

Changing the nitro amount is one of those things.

Some people see a balky engine run better with more nitro. Some see their balky engine run better with less nitro. Some see a good running engine run sour with more, some see theirs go sour with less. Why?

The percentage of nitro has an effect on the timing of our simple engines. And some engines benefit by the timing change, while others don't like the timing that results. Sometimes we've got the wrong prop on the engine and getting a bit more rpm and better timing makes that prop into the right prop. Sometimes the cooling isn't great and pumping more fluid into the cylinder solves that problem somewhat. Sometimes the plug we got in the head likes the lessened heat of combustion, sometimes the increased heat of combustion keeps a too cool plug warm enough to last through idle periods.

Nitro amounts always seem to encourage discussion. Truth is, there ain't no magic nitro amount as long as we have so many other variables. And if there is one thing we got in spades, it's lots of other variables. Lots.
Old 09-01-2008, 06:09 AM
  #16  
Rudolph Hart
 
Rudolph Hart's Avatar
 
Join Date: Apr 2008
Location: Perth, AUSTRALIA
Posts: 4,383
Likes: 0
Received 1 Like on 1 Post
Default RE: 5% or 10%

In spades.Makes this hobby so interesting.
Old 09-01-2008, 10:41 AM
  #17  
JohnBuckner
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,441
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%


ORIGINAL: KW_Counter

When I lived below sea level I used 10% in my two strokes.
Now I live above 2,500 feet and those same engines require 15%.
Use what they run on unless you have some special requirements.
Good Luck,
KW_Counter


I am a little surprised that this gentleman is the only one who seemed to understand the real value in different nitro contents in relation to one's elevation and even more important the actual density altitude of for that particular time at that particular field.

Density altitude certainly does dramatically affect affect all aircraft, propellers and engines as well. While I am no combustion engineer nor do I have to be to understand the obvious boost in power avaliable with various degrees of percentages and when use approriately at different elevations.

Many folks may tend to fly at one field forever or tend to fly at other at similar elevations and its certainly understandable to settle on one percentage or even (at low elevations) FAI fuel in engines without high compression to take advantage of that fuel.

However to suggest that folks who taylor their fuel for the elevation is silly or money wasteful is a bit arrogant in my opinion. I do fly regularly here in northern Arizona at fields from 520 feet Msl to 7000 feet Msl and the 7000 footer 25% is the norm for two strokes and makes the differance in being able to fly at all

At the 520 footer 10% does just fine and even 5% would make no real differance. However at my home field 3450 Msl to get the same performance as the fellow at the low elevation we need 15%.


The Differance is real, its obvious and it make no differance how you theorize desity altitude is important.

And remember the airplane responds to density altitude, not geographical elevation and on a hot summer day density altitude can easily exceed elevation by several thousand feet.


So in summary then yes if you leave competition purposes out. The most important and useful application of various nitro contents is of course tayloring to ones elevation, This is important, its not wasteful and its certainly not silly.

John
Old 09-01-2008, 12:44 PM
  #18  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 5% or 10%

Altitude certainly will matter. For some people.

How much it matters over in the UK certainly is another matter altogether. How high are the mountains there around Kent?

Arrogance???? All seemed genuinely trying to help.
Old 09-01-2008, 01:31 PM
  #19  
aerowoof
 
Join Date: Jun 2006
Location: pembroke, NH
Posts: 2,962
Likes: 0
Received 1 Like on 1 Post
Default RE: 5% or 10%

back in 1982 I got interested in ducted fans,back then they were fairly new territory and alot of advice was around like can't take off from grass,need 25% nitro burn out plugs veryflight.well I built a midwest jetster with a rk-20b fan unit and a k&b 3.5 on a tuned pipe.because of improper cooling of the head you could burn a plug out each flight but a simple fiberglass cover over the head solved that,a light weight airfram properly balanced would allow grass field take offs and I could use 10% fuel with out a significant change in performance at the elevation I was flying at.to me the difference in cost per gallon of misslemist vs 10% sport fuel was not worth it,granted there was an rpm increase about 500 but the increase in thrust was less than a 1/4 pound I had better luck adding a rpm rod,a 40 size peery carb and a robart mark 4 super pumperthis was a gain of 1000 rpm on 10% fuel and almost 1/2 pound increase in thrust.
Old 09-02-2008, 06:19 AM
  #20  
Rudolph Hart
 
Rudolph Hart's Avatar
 
Join Date: Apr 2008
Location: Perth, AUSTRALIA
Posts: 4,383
Likes: 0
Received 1 Like on 1 Post
Default RE: 5% or 10%

I agree with you all and the mod.Lot's of funny spelling in this thread..

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.