[mithiral67]

Guide to Measuring Ethonal Content in Fuel E85 and Calculators to Determine Mixes

With so many folks running some mixture of E85, I thought it would be a good idea if we have a how to guide here for measuring the content of ethanol in our gas. In addition, I thought it helpful to have a simple excel calculator that could quickly determine the amount of gas we should add to a tank of gas to hit a desired level of ethanol mix.

What’s in Our Tanks Anyways?
Pump gas usually consists of a small percent of alcohol/ethanol depending on brand, location and season, hence all the warnings that your pump fuel may contain up to 10% ethanol (federally approved to increase to 15% in the future). E85 is supposed to be 85% ethanol and 15% gas, but like regular pump gas, can have its ethanol content vary between winter and summer based on the manufacturers’ mix.

As such, it’s always important to know what percentage of ethanol is in your tank (unless you have a fancy flex fuel system, of which I have zero knowledge on how accurate these are).

Why is this important?
Running incorrect boost, timing and AFRs on your tune for the gas in your tank can destroy things you love, like your engine, puppies and baby pigs.

For example, here are some logs I had when I mixed up a tank of what should have been E30 on the Cobb E30 OTS maps. The timing drops made me pretty unhappy. I am sure that the “E85” I bought was actually 85% devils blood and not the promised turbo nectar of the Gods.

How to Measure E85
It’s not too hard to find instruction on measuring content of ethanol on the web, but most are all over the place on the examples and I wanted to provide a little more easy-to-use excel file to calculate the ethanol contact.

Attached is a pretty good pdf on what you should look for. Note, I use a 50 ml beaker. Its not about the size, but how you use it.

Here's a video as well. If you cant figure it out from all this, please dont use e85 and stick with regular pump.

For those curious, the basic concept is that if you combine water with E85 (or any combination of gas and alcohol/ethanol), the water and alcohol/ethanol will mix together and the gas will separate. Based on the amount of gas that separates, you can do the math to determine the percent of the fuel that was alcohol/ethanol.

What’s In the Excel File?

MACROS!!!! (See below)

The first table is used to measure the content of ethanol based on a sample of test fuel and water. Simply put a mixture of water and test fuel in a sealable container, then shake and bake (kidding about the bake part, please don’t bake). Let the mixture set for 5-20 minutes until a clear separation can be seen in the fluid, input the measurement of the separation. The formula will output the ethanol content of the test mix.

The second table will tell you the ethanol content of a tank of gas given the Test Fuel you just tested and a tank of gas.

The third table, my favorite and most practical, will tell you how much Test Fuel you should add to a tank of gas with a known ethanol content to hit a desired mixed ethanol content. Notes, we need the macros here to complete this calculation because as we add more fuel to the current tank, the calculation changes. Math is crazy.

See attached

Here’s a good tool for checking octane. I have noticed that if you use factions of gallons the calculations act weird and don’t compute per my math, so I would suggest using whole numbers. You will notice that my file doesn’t give a shit if you use decimal, it’s always happy to serve us humans.

http://www.intercepteft.com/calc.html

Cheers,
James

[mithiral67]

PS, you dont need to buy a kit, hit up a chemistry store, total costs for a glass beaker, glass funnel, and dropper was less than $20.

[joec500]

or a rig an Ethanol Composition sensor to your tune and never have to worry about measuring

[mithiral67]

That is not an option for everyone. As this thread is not about tunes, please leave that discussion elsewhere

[Tiago@VRSF]

Zeitronix makes a pretty good setup: http://www.zeitronix.com/Products/ECA/ECA.shtml

We ran this on our 9 second shop Evo and found that the ethanol content varied greatly depending on where it's purchased.

[joec500]

Originally Posted by mithiral67

That is not an option for everyone. As this thread is not about tunes, please leave that discussion elsewhere

I hear that, well another solution would be to rig up a composition sensor to just measure and display the content for you, so you can adjust your COBB tune (or whatever tune of your choosing) to the ACTUAL composition in your tank, and have pre-set Maps optimized for Ethanol in 5-10% increments.

This way you get a super precise measurement...just a thought.

I think a simple in-line Ethanol measurement solution that perhaps displays to something like P3 Cars Boost Gauge would be awesome.

[mithiral67]

Not a bad idea.

[V8bait]

Originally Posted by joec500

or a rig an Ethanol Composition sensor to your tune and never have to worry about measuring

Using an ethanol content sensor is a band-aid for proper flexfuel tuning logic in almost all modern examples, unless you just have money to burn. The DME does not have proper flexfuel tuning logic from the factory, and some aftermarket piggybacks don't have adequate logic for this either. No big deal, there are multiple ways to skin a cat. But that's beyond the scope of this discussion (lucky for the cat). I do like the idea of a gauge though, just because I'm sort of a data snob and I'm a bit lazy to do science after I get home from doing science all day

Back on topic- Measuring E85 ethanol content is very useful for knowing how much you are mixing, good job OP. It's always nice to know what you're mixing and to know what you have so that you can be consistent, regardless of tune, especially with how much E85 can vary from place to place and month to month.

[mithiral67]

Originally Posted by V8bait

Using an ethanol content sensor is a band-aid for proper flexfuel tuning logic in almost all modern examples, unless you just have money to burn. The DME does not have proper flexfuel tuning logic from the factory, and some aftermarket piggybacks don't have adequate logic for this either. No big deal, there are multiple ways to skin a cat. But that's beyond the scope of this discussion (lucky for the cat). I do like the idea of a gauge though, just because I'm sort of a data snob and I'm a bit lazy to do science after I get home from doing science all day

Back on topic- Measuring E85 ethanol content is very useful for knowing how much you are mixing, good job OP. It's always nice to know what you're mixing and to know what you have so that you can be consistent, regardless of tune, especially with how much E85 can vary from place to place and month to month.

I agree on not wanting to be constantly tweaking the map. I want a map for X ethanol and get the right fuel in off the bat. I am getting an E50 etune. Will just mix aiming for e50 based on my last sample, but grab a sample each time I fill up. Then baby it home to confirm it’s a good mix (and to know what’s in the tank when I mix my next tank). If what I added is lower than I had expected, I will just switch to the OTS E30 map for the tank and correct with 93 as needed.

That being said, a sensor under the hood with a gauge I just plug in after each fill up for a spot check from time to time would be nice. I only fill up 2-3 times a month as is and will only run e85 during the summer; I don’t mind the extra effort. Probably the same amount of time I would need for maintenance upkeep of a meth kit.

[joec500]

Originally Posted by mithiral67

I agree on not wanting to be constantly tweaking the map. I want a map for X ethanol and get the right fuel in off the bat. I am getting an E50 etune. Will just mix aiming for e50 based on my last sample, but grab a sample each time I fill up. Then baby it home to confirm it’s a good mix (and to know what’s in the tank when I mix my next tank). If what I added is lower than I had expected, I will just switch to the OTS E30 map for the tank and correct with 93 as needed.

That being said, a sensor under the hood with a gauge I just plug in after each fill up for a spot check from time to time would be nice. I only fill up 2-3 times a month as is and will only run e85 during the summer; I don’t mind the extra effort. Probably the same amount of time I would need for maintenance upkeep of a meth kit.

or a little display you can mount in your ashtray or something, that way you have real time data to make adjustments as needed, as the mixture reading could change as your drive around and things mix around.

[mithiral67]

Well, nothing will change over a tank of gas, so why would I need live data all the time?

[joec500]

Originally Posted by mithiral67

Well, nothing will change over a tank of gas, so why would I need live data all the time?

you mentioned getting a reading under the hood when you fill. I would assume it would change as it starts mixing together, unless you get the reading after you have driven around a bit. Again I am not a chemical expert, so perhaps the moment you fill the reading could be accurate. I just assumed some of the mixture would have to pass the sensor to get the most accurate reading, and if you had real time data, you could see when it stabilizes.

[mithiral67]

I honestly dont know how long it takes. But when I added 2.5 gallons of e85 to 5 gallons 93 while sitting on a dyno, I was able to do a pull on the dyno after idling for 5 mins and the logs looked like it has mixed pretty good. I am guessing driving around will accelerate that pretty quickly.

But once mixed, the % wont change. So, to save the effort of running anything into the cabin, I would think something just in the engine bay would be fine.

[enrita]

just get an upgraded lpfp and run 100% E85, problem solved. Otherwise keep always E50 or E60 and tune slightly conservative in terms of timings to avoid corrections on less E%

[Tiago@VRSF]

Originally Posted by enrita

just get an upgraded lpfp and run 100% E85, problem solved. Otherwise keep always E50 or E60 and tune slightly conservative in terms of timings to avoid corrections on less E%

That's a great solution but you'll be surprised to see the discrepancy between different E85 vendors where some might show as true E85 vs another showing a lower ethanol content.

[N54Society]

On the fence between getting an ethanol sensor or just getting the Stage 2 pump and pumping 100% E85. :/

[TrollToll]

Originally Posted by vbp6us

On the fence between getting an ethanol sensor or just getting the Stage 2 pump and pumping 100% E85. :/

You're going to need port injection for that, too.

[N54Society]

Originally Posted by Yournamehere90

You're going to need port injection for that, too.

For 100% E85, right?

[TrollToll]

Originally Posted by vbp6us

For 100% E85, right?

Yes

[cwarren]

Not sure why people trip on the % thing so much . I have checked my local station on many occasions and is true e85 every time . I asked owner if it ever changes with seasons " nope only in very cold climates " and this has been true for a few years now .
I'm pretty sure you can get it down within 5% or so just calculating your fill ups . Your not detonating your car with a give or take 5% ethanol .

[Kienvu14]

Originally Posted by cwarren

Not sure why people trip on the % thing so much . I have checked my local station on many occasions and is true e85 every time . I asked owner if it ever changes with seasons " nope only in very cold climates " and this has been true for a few years now .
I'm pretty sure you can get it down within 5% or so just calculating your fill ups . Your not detonating your car with a give or take 5% ethanol .

We here in Colorado have stations that vary extremely. Some have experienced as low as e50-e60 from "e85" because of crappy quality winter blend. Then I've seen consistent e70 winter blends as well. So that's why every one test here