can someone tell me why my figures dont add up.? what did I do wrong.?

1 gallon approximately = 128oz
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1% of 128 = 1.28oz (castor oil)

18% of 128 = 23.04oz (synthetic oil)

10% of 128 = 12.8oz (nitro)

69% of 128 = 88.32oz (Methanol)


Add 1.28 + 23.04 + 12.8 + 88.32 = 125.44oz = 1Gallon

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FAI Fuel
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1 gallon approximately = 128oz
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70% of 128 = 89.6oz (Methanol)

20% of 128 = 25.6oz (synthetic oil)

Add 89.6 + 25.6 = 115.2oz = 1Gallon

What are you trying to add? Your percentages do not add up to 100%

Thats what I'm trying to find out why they don't add up.? Shouldn't the onces of each add up to 128oz/1Gallon

Monkeybone:

Your final calculation figures look fine to me - considering in the first forumula you are only mixing 98% of a gallon (69% + 10% + 18% + 1%) and in your second formula you are only mixing 90 % of a gallon (70% + 20%). If you add 2% of something to the first forumula and 10% of something to the second formula then you should calculate to 128 oz gallons.

Your mix percentages on the left side have to equal 100% or your final calculations cannot equal 128 oz (full gallon).

Dan

Yep..
1% + 18% + 10% + 69%= 98%

In the first case;

1%+18%+10%+69% = 98% NOT 100%

It follows therefore that 98% of 128ozs = 125.44ozs

Why 98% of 1 gallon doesn't equal 100% of 1 gallon should be obvious.

In your next "FAI Fuel" calc;

70%+20% = 90% NOT 100%

90% of 128oz = 115.2oz

Again why 90% of 1 gallon doesn't equal 100% of 1 gallon should be - obvious.

Other than overlooking the fact that respectively neither 98% or 90% are equal to 100% of anything, your arithmetic is correct. [sm=spinnyeyes.gif]

Thanks for the info guys I got it straight... I forgot to save my note pad file after I done some changes to it. (to many long nights brain starting to shutdown)

Gentlemen:
The correct way to prepare any volume to volume solution, in this case glow fuel, is first to add the lower concetration components ( as already been calculated) to about 1/3 to 1/2 of the methanol volume in a reservoir into which a mark to the 128 oz ( 1 US Galon in your case) capacity has been done. Then you mix what you have added so far, and continue adding the methanol, mixing while adding it, until you reach the 128oz mark done to the holding jug ( or whatever you use) This is the correct way of doing any volume to volume solution. There could be molecular attractions ( or repulssion) between the liquids that could cause you to end up with a little more concetrated mix( or a less concentrated mix) than you want if you go by the mathematics only way. While this may be a small deviation, you may save some $ . I think that comercial manufacturing uses a convertion and prepare the fuels in a weight by weight system because is easier and more accurate concentrations can be achieved. My 2 cents of chemistry. BTW I mix my own fuel, but use the metric system which is easier and basicly error free.

Angel Ramos
Arecibo, Puerto Rico

Yes. But the biggest thing people forget is that methanol has the largest coefficient of expansion of all of the components. If you mix say 20% nitro by volume at 70 degrees, then it becomes less on a hot day, say 18% by volume. Good idea to keep this in mind if mixing on a hot or extra cold day. I think VP and some racing sites have charts to make this adjustment. IMO its not a big factor to me, just subtract a little nitro on a hot day, or live with it. Could be a factor if you are a pylon racer though.

According to my research, the coefficient of cubical (thermal) expansion for nitromethane is slightly greater than the coefficient for methanol, and both are about 50% greater than the coefficients for castor oil and synthetic oil. If all of the ingredients are at the same temperature when mixed, the temperature related differences in % by volume values are in the neighborhood of 0.1%, not 2%. If the ingredients are at different temperatures when mixed, the errors can be greater, but still not significant unless the temperature differences are extreme.

Actually I'm not sure this is the actual volumetric liquid expansion in the jug so to speak. But also the way they vaporize and burn when they are actually burn. I recall seeing some correction charts somewhere, but may have been some time ago and not sure where to look on the web. Maybe just sold through racing fuel dealers. I recall charts to correct for mixture at differant temperatures also. But maybe nowadays they use computer control for that.

There is molecular bonding taking place in the fuel. If you mix by volume you WILL end up with slightly less than 128oz but the mix will be correct.

There is another method of mixing fuel by weight that will yeild exactly 128 oz but i am not familiar with it.

In drag racing all mixing is by weight. They use hydrometers to check the fuel. That may be one differance. But also they must make mixture adjustments if going up and down in nitro. You may go up in nitro if the track has a lot of traction and down if not for example. I may be recalling the effect of the methanol evaporating better if the fuel is warmer. This would have the effect of having less nitro requiring a slightly leaner mixture. That is because the nitro doesn't vaporise as well, and doesn't change as much with temperature.

Now I didn't mean my example to be an exact number either. I am recalling this stuff from back when and may have mixed it up somewhat in my head. But I do recall some differance with temperature.