Fuel formula?

[minnesotamodeler]

Been having trouble finding the right fuel for my old 1/2As...all I could find was 5%, 10%...I want something with higher nitro for those little engines.  LHS had some Cox fuel, in quarts only, for $10, seemed a little pricey ($40/gallon!). 

 So I found an RC car racing shop and bought some "Blue Thunder Racing Fuel", 30% nitro.  Problem being, I want to add a little castor for these old engines, but I can't find what the oil content is I'm starting with.  I appreciate a business wanting to keep its proprietary info to itself, I don't want the whole formula, but I need to know the oil content (and type).  Anybody?

I ain't running it til I know what's in it.

--Ray

[Alan Hahn]

What has been suggested before is to measure out a small quantity of fuel. Now let the alcohol and nitro evaporate. What is left is the oil.

My understanding is that the RC Car guys run with very little oil, and for some reason 12% comes to mind.

I know this isn't definitive, but maybe you can check the web sites of places like Sig and see what they say they put into RC Car Fuel. That probably gives you an upper limit, since I think oil and nitro are the main costs in fuel. Since they say 30% Nitro, they may be skimping more on the oil by using more methanol. Another thing to consider is whether you measure by weight or volume. I know that nitro is heavier than oil or methanol, so one trick for manufacturers is to quote %'s by weight, since their nitro % will sound better. Places like Sig quote by volume. I am not sure about the relative weight of Oil vs Methanol. I am sure the Car Fuel is mainly or all synthetic since RC types (I am one!) tend to equate castor messiness as a big negative when it comes to cleanup.

[Peter Ferguson]

The fuel you mentioned has castor and synthetic in it according to their advertisements but, as you mentioned, it doesn't state the amount. Call Horizon I'm sure they would know since they developed it or call Morgan fuels they worked with Horizon on it.

http://www.horizonhobby.com/Articles/Article.aspx?ArticleID=1198

[Bob Reeves]

Tried to find out what the oil content of a car fuel was a couple years ago.. Was told by the manufacture it was a company secret but did find out enough to know it was really low. I gave it to a friend that ran cars..

If it is 12% adding 14 ounces of oil will bring it up to about 20% oil 27% nitro.

[Pinecone]

I just picked up some Byron 1/2A fuel from the LHS.  It only comes in quarts, it was marked $12.99, but they have a buyers club that includes fuel discounts.

25% nitro, 16% all castor.

[ray copeland]

Ray, i have been running WildCat Eliminator made for cars for over a year in my little Norvels.  20% nitro and 18% castor / synthetic blend.  No problems at all.  $24.99 a gallon and is available at the local shops that cater to RC. I also keep a quart of Norvel brand 35% nitro from Va. hobbysport for my Rumbler and other combat 1/2a's . 

[kenneth cook]

       Ray, Tower Hobbies doesn't always list it in their items but they do stock Sig fuels in qts only. I've had real good success with the SIg 25%-35%. The local store nearby stopped carrying the SIg fuels which was a real dissapointment to me. They just started carrying the Hobbico fuel for 1/2 a's. Nobody could tell me the oil content of that particular fuel. I just happened to be browsing on the Tower site one day when I noticed the 25% SIg fuel. I'm using this fuel mostly in my Cox engines. I found the 25% seems to be a bit more forgiving to the stock glow plugs. I use the 35% in my tee dees. The only drawback is the price your paying for the quarts. I believe the last time I purchased some which was a few months back it was in the 7$ range. My son and I can really burn up some 1/2 a fuel.  Ken Cook

[minnesotamodeler]

Well, I learned the fuel I have is 10% oil--shameful, if you ask me.  So I need to add about 18 oz. of castor to get it up to the 20-22% range I want; puts the nitro down to the mid-to upper-20s, good enough.  Up side is, I now have over 5 quarts of fuel!  Thanks to all for your quick responses.

[Brian Hampton]

Adding oil doesn't really change the nitro content. With that Blue Thunder fuel having 10% oil and 30% nitro it leaves 60% methanol. That means 1 part nitro to 2 parts methanol (which is all the engine uses to actually run on) so really the nitro % of the FUEL part of the total mix is 33%. Add as much oil as you like and the FUEL mix (the nitro/methanol %) stays exactly the same. Because the extra oil takes up some volume the needle has to be opened a little more to regain the original volume of nitro/methanol flowing through the needle valve.That's all the engine wants.

[Bill Adair]

Add as much oil as you like and the FUEL mix (the nitro/methanol %) stays exactly the same.

Are you sure about that?

See the link I posted to find out what adding 18oz of Castor oil does to Ray's fuel.

Ray started with 30 percent nitro, and 10 percent oil.

Ray now has 26.3 percent nitro, and 21.55 percent oil.

Bill

[Bill Gruby]

 Ray;

  This may or may not help you. You have to know what you have by volume to start with to use it. Plug in the numbers and it will tell you what you need to add, be it Nitro or Oil.


 http://www.nitrorc.com/default2.asp?Introduction=http://www.nitrorc.com/fuelws


  "Billy G"

[minnesotamodeler]

... I need to add about 18 oz. of castor to get it up to the 20-22% range I want;...  Up side is, I now have over 5 quarts of fuel!   

My mistake, funny no-one noticed, or at least bothered to correct:  32 oz. in a quart, dummy...so I now have about a gallon and a pint...

[minnesotamodeler]

OK I finallh got  to run my "doctored" fuel today, in my 1/2As.  Ran very well although not noticeably better than the 15% I had been using.  Everything did seem to start a little more readily, which is a significant plus in 1/2A!

Final figures after doctoring:  26% nitro, 22% oil.

[RC Storick]

Well, I learned the fuel I have is 10% oil--shameful, if you ask me.  So I need to add about 18 oz. of castor to get it up to the 20-22% range I want; puts the nitro down to the mid-to upper-20s, good enough.  Up side is, I now have over 5 quarts of fuel!  Thanks to all for your quick responses.

1.28 oz per percentage so 12 X 1.28 = 15.36  So if you add 15.36 oz of oil to 10% fuel. Brings 10% fule to 22 %

[minnesotamodeler]

Well, the complication is, when you add, say, 15 oz. of oil you're suddenly working with 143 oz. rather than 128 oz., so it takes a little more yet to get to the percentage I want...namely 3+ more oz. yet, total 18 (I actually used 19).  With 147 oz., it is 1.47 oz. per percentage point.  for +12% it = 17.64, close enough.  Maybe I have closer to 23% oil.

But that is an interesting, and very handy way, of calculating it.  A guy could just about do it in his head. Just have to remember you're adding to the total quantity as well as percentages.

[Mike Spiess]

Here Ray try this
http://www.nitrorc.com/default2.asp?Introduction=http://www.nitrorc.com/fuelws

Go to the bottom of the page.

[minnesotamodeler]

Mike, Bill Gruby also posted this link, a few msgs above.  It is very handy, for sure.  Worth looking at twice!?!