fuel question

I have a gallon of fuel, 10% nitro, 20% castor oil. How much more castor oil needs to be added to bring the oil content up to 28%?
thanks

I think if you add 10 oz of castor with out taking anything out of the original gallon you will be right at 28 %

Here's a formula for deriving oil needed to boost fuel from % of oil present to % of oil wanted
Where:
C= % of oil current
X= oz. of oil added
Y= % of oil desired
all measurements in oz.
and figured for 1 gallon fuel (128 oz.)

128Y - 128C = X - XY

Solved for 20% oil to 28% oil
128(.28) - 128(.20) = X - .28X
35.84 - 25.6 = .72X
10.24 = .72X
14.222 = X

You need to add 14.222 oz. to move 20% oil to 28% oil.

Nitro reduction formula where
C = %Nitro present
X = still equals added oz. of oil
R = reduced Nitro %
R = 128 * C / 128 + X
with the 20% to 28% change and 10% nitro fuel
R = 128(.10) / (128 + 14.222)
R = 12.8 / 142.222
R = .090001sumptin or 9% nitro
These formulas work with any percentage of nitro or oil. As long as you know where you are, you can get where you want to go. I might add that if you are looking to boost nitro, just use the first formula for nitro instead of oil, be careful though, you will lower oil content when you add nitro. I snatched this off RCOnline CL forum several years ago. Steve

Altering fuel is actually a bit tricky. Depends on just how accurate you want to be. Here's your example:

You're starting with "a gallon of fuel, 10% nitro, 20% castor oil".
Here's the breakdown of what's actually in that gallon:
Note: 1 gallon = 128 total fld.oz.
nitro - 12.8 fld.oz. - 10% (of 128 total oz.)
oil - 25.6 fld.oz. - 20% (of 128 total oz.)
methanol - 89.6 fld.oz. - 70% (of 128 total oz.)

If you add 14.222 fld.oz. of oil, as Steve says, you will then have a total of 142.222 fld.oz. of fuel (128 plus 14.222)
The breakdown will be:
nitro - 12.8 fld.oz. - 9%
oil - 39.822 fld.oz. - 28%
methanol - 89.6 fld.oz. - 63%

So now you have the 28% oil you want, but your nitro percentage is down to 9%.

The answer is to take your base gallon of fuel and add 14.9 oz. of oil AND add 1.7 oz. of nitro.
You will end up with 144.6 oz. of new fuel that will be:
nitro - 14.5 fld.oz. - 10%
oil - 40.5 fld.oz. - 28%
methanol - 89.6 fld.oz. - 62%

I certainly agree about %'s of stuff, but naively I would think that as long as the combustables (Methanol and nitro--ignoring any burning of the oil) keep their same ratio, the oil is nominally just along for the ride. So after you open up the needle to compensate for less combustables, I would think that the power you see with more oil would not be that different than with the fuel before you added the oil.

If you increase the nitro too, I would think that this new mixture would actually make more power than the original gallon jug. In other words it would turn the prop faster once you reset the needle.

I know that as a fuel manufacturer, those details are really important , so I understand what you are saying.

Give the attached spreadsheet a try.
I have been boosting the oil content of the fuel I am running in my half-a's, and wanted a more accurate/quicker way of figuring the correct amount to add to get a specific oil percentage. I also added one that will allow you to bump nitro percentage, and finally one that does both.

If you have any difficulty downloading it, let me know and I can email it to you.

(If any of the experts out there want to check my formulas, please do. I have checked it over and over again, but then again....)

There is also a spread sheet on the Tulsa site at http://www.tulsacl.com/WorkShop.html

I know where to get castor and synthetic oil, but what is a source for Nitro??

thank you all for your input and for the fuel calculator. This SSW board is THE place for info.
Will

LAST EDITED ON Jul-11-03 AT 09:51 PM (CDT)
 
I had forgotten about the Excel spreadsheet on Tulsa GD CL Website, but received an email from Catdaddy, reminding me. He also pointed out that it gave the answer of 10 oz., not 14.222 oz. I couldn't figure out how to work it in a couple of minutes, not being very proficient on Excel, and gave up. I did calculate the oil required, NOT using the formula, but just figuring it out myself, and came up with the same 14.2222222 oz. One or the other is wrong, can't say which for sure. But I don't trust MS Excel very much. Steve

LAST EDITED ON Jul-11-03 AT 10:40 PM (CDT)
 
>Give the attached spreadsheet a try.
>I have been boosting the oil content of the fuel I am
>running in my half-a's, and wanted a more accurate/quicker
>way of figuring the correct amount to add to get a specific
>oil percentage. I also added one that will allow you to bump
>nitro percentage, and finally one that does both.
>
>If you have any difficulty downloading it, let me know and I
>can email it to you.
>
>(If any of the experts out there want to check my formulas,
>please do. I have checked it over and over again, but then
>again....)
>
>

Matchlessaero wrote the above in post #5. I couldn't copy and paste to re-post the link, but had this result:

I downloaded and worked the program as directed. Changed to 10% nitro, 20% oil, 70% alcohol and 128oz. So far, so good. Changed the added ounces of oil in the red box to 10.0, 14.222, etc., and everything changed except the oil percentage content. The oil, nitro, alcohol and total (ounces) all changed as planned. The nitro and alcohol percentages also changed per expectations. Can't fathom why the oil percentage didn't change. Steve

EDIT: AHHAAAH! You just have to click on the box that you want to change. Wonder why the others changed by themselves? Anyway, it sez the 14.22 oz is the correct amount to add to get 28%.

PS: Nice website!

Source of nitro? Klotz sells it. Look on their web site and see if there's a dealer nearby. Also, if you get to know a drag racer, they often will have a gallon or two left over at the end of the season.

LAST EDITED ON Jul-12-03 AT 06:45 PM (CDT)
 
There was a previous thread on the subject of where to find fuel makin's. The Search Function should find it. Bob Smiley was the originator of the thread. I think it was June or July '02. Steve