11-29-2012, 06:25 PM #1
Questions on measuring ethanol content
New to playing around with E85 and wanted to make sure the method I'm using is accurate. I'm using the 100ml tube where you add say 25ml of water then add the mixture in to fill it up to 100ml, shake and watch the separation line and then do basic math. I filled up a 30 gallon barrel with E85 since the nearest station is 30 minutes away. After measuring the contents of the barrel I'm coming up with E89.3 which makes me happy if it's accurate as I was afraid I might have gotten E75 or something low for the winter. The tank I already had in the car I had already adjusted to where my logs were clean but couldn't get a hose down far enough into the tank to siphon off so I had to add 6 gallons of fresh gas to get it high enough to siphon some off to test. I had a 1/4 tank and running through the testing showed by new tank was only at E12 and trying to do backward guess work I came in that I had previously only had maybe an E25 mixture in the tank.
So my questions would basically be is this method really accurate and if so does it really only take E25 this time of year (texas in the 70's) to make the E30 Cobb mapp happy?
Any easier way to pull fuel samples other than a cheap siphon pump as it seems tricky to get that hose down in there where it actually gets anything.
11-29-2012, 07:30 PM #2
Honestly, how I measure it is I know that I have a tank with x amount of fuel, if the tank is half empty I add x amount of E85, and tune the car to that amount. I always use 50% so if there is 1/4 tank i add 1/4 tank of E85.
11-29-2012, 07:39 PM #3
11-29-2012, 09:41 PM #4
11-29-2012, 10:18 PM #5Guest Vendor
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11-29-2012, 10:24 PM #6
Check your E85 pump the next time you pass through. There's usually a legal disclaimer saying that the lowest the ethanol content will be is 70% (kinda like on this one):
Attachment 22636COBB AP ProTune by Bren of ///Bren Tuning
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11-29-2012, 11:16 PM #7
11-30-2012, 08:21 AM #8Member
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FWIW, it's ok to calculate for the minimum ethanol (E70) if your "greater-than" margin of error will end up below the E50-E60 threshold of the OEM fuel tables, the excess ethanol content from running E85 vs. E70 is just an additional power and cooling benefit.
You're running COBB E30, which IIRC reflashes the fuel table for that map which allows for a higher margin of error.
Basically what I'm saying is that the E30 should be safe to run up to max fuel trims which is usually E50 - E60 ethanol content (depending on fuel tables), it's just not safe to run lower than E30.
Last edited by spool twice; 11-30-2012 at 08:26 AM.Loe P.
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11-30-2012, 09:12 AM #9
I actually thought about installing some kind of fuel test fitting in the low pressure line leading to the hpfp. Possibly a tee to a ball valve. That way I could open up the valve, and cycle the fuel pump to get a sample to read.
I do agree also with what you are saying. As long as the ethanol content of your fuel tank is in a certain range, everything should be fine. The fuel trims make this possible. However, I still think it's good to sample the tank periodically because when you fill up, you have to know the ethanol content of the current fuel to know the ethanol content of the tank once it is full. If you are estimating the current ethanol content based on past a fill up, your error could increases with each fill up. A test of the fuel in the tank would let you know exactly what the ethanol content is. Of course if you routinely run your tank down all the way before fill up, this matters much less.
11-30-2012, 10:01 AM #10
Not sure if you have a spare $600 laying around, but if i ran E85 more often i think i would look into purchasing this - http://www.zeitronix.com/Products/ECA/ECA.shtml
The analyzer is $199, and they sell the same Flex fuel sensor as the one used in Shiv's E85 kit for $359. An 8 Ft wiring harness is $29. Plop that bad boy in your glovebox and you are golden.2011 E90 M3 \ Melbourne Rot Metallic
11-30-2012, 10:07 AM #11
12-01-2012, 06:42 PM #12
01-30-2013, 11:14 PM #13
Bumping and old thread, but through this might be helpful to you folks. http://www.bimmerboost.com/showthrea...etermine-Mixes2015 - Cayman GTS - Stock
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