Check my fuel math?
I need fuel with 7% oil by volume.
I have Powermaster 15% Sport fuel, which is 18% oil by volume. My math is as follows: 128 oz of fuel = 86 oz of methanol 23 oz of oil 19 oz of nitromethane If I take 16 oz of the fuel, I have: 10.725 oz of methanol 2.875 oz of oil 2.4 oz of nitromethane The above is still 18% oil by volume. Now, by my calculations, if I add 30 oz of pure methanol to the 16 oz of this Powermaster fuel, I will have: 46 oz of 7% oil by volume, fuel. Which would be: 40.725 oz of methanol 2.875 oz of oil 2.4 oz of nitromethane Anyone see anything wrong with my math? Thanks! :) 
RE: Check my fuel math?
Quote:
ORIGINAL: Kmot I need fuel with 7% oil by volume. I have Powermaster 15% Sport fuel, which is 18% oil by volume. My math is as follows: 128 oz of fuel = 86 oz of methanol 23 oz of oil 19 oz of nitromethane If I take 16 oz of the fuel, I have: 10.725 oz of methanol 2.875 oz of oil 2.4 oz of nitromethane The above is still 18% oil by volume. Now, by my calculations, if I add 30 oz of pure methanol to the 16 oz of this Powermaster fuel, I will have: 46 oz of 7% oil by volume, fuel. Which would be: 40.725 oz of methanol 2.875 oz of oil 2.4 oz of nitromethane Anyone see anything wrong with my math? Thanks! :) When mixing in odd quantities, I use graduated cylinders and measure in mL instead of fluid ounces as its easier to be more precise. 
RE: Check my fuel math?
And the answer is........ Add 201 oz methanol to a gallon of the Powermaster fuel, or 47 oz of methanol to 30 oz of the Powermaster to get a final product containing 7% oil and 5.8% nitro. In other words, multiply the starting amount of Powermaster by 1.57, and that is how much methanol to add to it.

RE: Check my fuel math?
Thanks for the replies guys! :D
Let me try to understand this. You are dividing the 46 oz total fuel by the oil content of 2.875 oz to get the oil by volume of 6.25%, correct? The way I look at it, the 46 oz total is not the figure to use, but instead the 40.725 oz of methanol is. Because that is actually how much methanol there is. When this is calculated with 2.875 ounces of oil, the oil by volume becomes 7%, does it not? Why am I unable to understand this? [&:] 
RE: Check my fuel math?
To calculate the percent by volume on any component of the fuel, you divide the amount of that component in the fuel by the total amount of fuel, not the amount of methanol. In your original post, you multiplied the percent of oil in the gallon (18%) by total amount of fuel (128 oz), to get the amount of oil in the gallon, right? If I gave you 46 oz of fuel and told you it was 7% oil, wouldn't you calculate the amount of oil in that 46 oz of fuel the same way?

RE: Check my fuel math?
Quote:
ORIGINAL: hauckf To calculate the percent by volume on any component of the fuel, you divide the amount of that component in the fuel by the total amount of fuel, not the amount of methanol. In your original post, you multiplied the percent of oil in the gallon (18%) by total amount of fuel (128 oz), to get the amount of oil in the gallon, right? If I gave you 46 oz of fuel and told you it was 7% oil, wouldn't you calculate the amount of oil in that 46 oz of fuel the same way? 
RE: Check my fuel math?
DING!
Now I get it. Thanks! :D 
RE: Check my fuel math?
Quote:
ORIGINAL: Kmot DING! Now I get it. Thanks! :D 
RE: Check my fuel math?
Glad we could help. Now I have a question: What is fuel with 7% oil used for?

RE: Check my fuel math?
Will be testing a special intake manifold for the ASP radial engine. Like the Seidel and Moki engines, it allows the use of 7% oil fuel.

RE: Check my fuel math?
Tom can you keep us up to date on the manifold? i've run a friends 770 and it's been hard to keep the lower cylinders lit evenly till we added 7% unleaded petrol to the mix.
Cheers,peter 
RE: Check my fuel math?
<span style="fontsize: medium">Hey Old Fart:
I have a Saito 325 and an ASP 400 sitting waiting for this slow oldbuilder(me) to finish the planes. Have been mixing my own fuel for many years. Usually use it in my Saito 4strokes and a few 2strokes I fly on occasion. I use 20% oil(10% castor and 10% Klotz), and 10 % Nitro. I can mix fuel for less than $8.00/ gal. I have heard of using 5~ 7% gasoline to give the glow engines a little "kick". Have you had a bit of experience with the addition of gasoline to the glow fuel mix??? Have a couple of twin Saito 4cycle motors that sometimes one of the cylinders will loose the "fire" when I throttle down to half when on the back side of a loop and the motor continues to run at 1/2 speed, running on just one cylinder. The only way to get the dead cylinder to relight is to chop the throttle a bit and the McDaniel glow plug controllerfires up the glow plugs.</span> 
RE: Check my fuel math?
Quote:
ORIGINAL: Old Fart Tom can you keep us up to date on the manifold? i've run a friends 770 and it's been hard to keep the lower cylinders lit evenly till we added 7% unleaded petrol to the mix. Cheers,peter 
RE: Check my fuel math?
Peter,
I ran the engine today on the blended 7% oil fuel and the custom intake manifold. The engine runs just fine on this fuel. No smoke in the back yard either! :p Report and video coming soon. 
RE: Check my fuel math?
Try this site when mixing fuel. http://www.nitrorc.com/fuelws/allmix.asp

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