Calculating E30 and other Ethanol mixes. Math and derivation

[HBEcoBeaST]

Wtf that was supposed to be the easy way? Lol

I wait till I'm at a 1/4 tank or less, then I put in 3 gallons of E85 then round up to the next whole dollar. Then I top off the rest with 93. My ltft stays at +/- 5%.

If I really, really ran it down to e, then I will put in at least four gallons of E85. Y'all make it way too hard.

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That's basically what I do except I'm on CA 91. I've gone over 4 gallons of e85 plus mild octane booster with no issues.

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[Prixlyst]

It's all good. I appreciate the time and effort Prixlyst has gone through to think it through and share his work, it's this creative passion that drives enthusiasm in the platform. There's certainly use for it, however I don't think it's fair to downplay the effectiveness and usefulness of an actual gauge. I don't really use calculators, after mixing fuel and the pumps numerous times I have a good idea of how many gallons I need to mix between pumps (91oct and e85) and use the gauge to confirm I'm safe.

I never meant for this to be a "Gauges are useless" thread. This was something i was trying to find, and when i couldn't, I decided to put it out for other people. I completely agree that in the ideal setup one would have a gauge--it is definitely good to have something confirming your mix. It also comes down to preference: do you want to check the ethanol before you put it in your car with a little messy tube you have to fill up, or a nice clean and simple gauge like you have? Either work perfectly fine if you use them right.

I also didn't mean for this to be an argument, rather a solution. To me it looked like people were worried about running E30 because they didn't have a gauge. "Unnecessary" does not mean useless, but i do stand by the fact that as long as you are checking the E85% beforehand with a tester and you do the math right, no matter what boost you run, you will have the correct percentages in your tank.

 

[koozy]

here's an excellent way to verify if the E mix in the tank is good for the tune one is running with just an Accessport or capable OB2 reader.
http://www.fiestastforum.com/forum/...cussion-Thread?p=171604&viewfull=1#post171604

and here's the pioneer of the diy gauge kit.
http://www.fiestastforum.com/forum/threads/2870-Ethanol-percentage-hardware-project