Trying to mix castor to fuel for 1/2a cox engines

is there a math formula which calculates the % of oil in fuel to add to a batch to end up with N% oil in fuel and what the added castor decreases the nitro content to?

Example.

32oz car fuel 35% nitro 12%oil

If I added 3ozs castor to the 32 oz fuel I end up w/ 35ozs total mix
it would bump my oil up to 19% but dilute my nitro to 32%- (this is in strict adherence of the laws of mathamatics in accordance to RocketRob)

I sortof fumbled through this one and wished I had a real formula to solve for both the amount of oil to add to end up with a predetermined oil percentage and the effect on nitro percentage.

Is nitro available as an additive to bump the nitro back up?

Thank you in advance - my brain is tired

found info with this link that links to info on hbbuddy free prog that makes mixing very easy in weight volume any amounts generally

http://www.rcuniverse.com/forum/fb.asp?m=2913229
hope that helps

Balsaeater

Just to put your mind at ease, if you add oil then it doesn't change the nitro/methanol ratios at all. The fuel part of the mix is only the nitro/methanol which will keep their own relative ratio no matter how much oil you add. The nitro/methanol volume is the only thing the engine is concerned about for a proper tune so by adding oil you only need open the needle valve a little more to compensate for the extra oil and keep the same volume of nitro/methanol flowing into the engine.

Thanks Guys,
Downloaded the program and looks like I'll get more familiar with my conversions....

I had just assumed the nitro was a percentage of total fuel - thanks for setting my straight!

RocketRob,
Here is a link you might be interested in: http://www.nitrorc.com/
scrolll down to custom fuel blending workshop and click on it.
that should take you to an easy comp program. Scroll down to the bottom of the page to get to the choice to add oil & nitro or just add oil.

That's actually the way it's always done but it's also where it causes confusion. Say you had a fuel with no oil and was 50/50 nitro/methanol, it'd be called 50% nitro. I'll work in litres here because it's soooo much easier . Take 800ml of that fuel, that's a mix of 400ml of nitro and 400ml of methanol. Now add 200ml of oil and you now have 1 litre of fuel. The oil content of that total fuel is 20% (200ml in 1 litre) and the nitro content of that fuel would appear to be 40% (400ml in 1 litre) so it'd be marketed as 40% nitro. The remaining 40% is the methanol. But 40% nitro and 40% methanol still leaves an equal amount each of the fuel part of the mix. No matter how much oil you add to the blend then the nitro and methanol always remain the same 50/50.