Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Was just reading through this today, see link below for full "E85 Handbook" if you care for a bit of reading on the subject.

https://afdc.energy.gov/files/u/publ...l_handbook.pdf

What struck me is this seasonal volatility chart. From what I gather, E85 now comes in 4 classes (used to be 3) based on ethanol content. Or at least, there used to be a minimum ethanol content for each class, but they've changed that so now the classes are based on vapor pressure. Because of this change, essentially any time of year you pump E85, you could be getting anything from 51% to 83% ethanol as long as they meet the vapor pressure requirement.

Here is the way the 3 classes used to be set up.

Class 1 - 79% ethanol minimum
Class 2 - 74% ethanol minimum
Class 3 - 70% ethanol minimum

Of course, now these could be even less and they've added a class 4, which we can assume will likely be somewhere in the 50-60% range.

This is somewhat alarming, especially for those of us in colder states where we are getting classes 3 and 4 most of the year. Without testing ethanol content each time we fill up, or running a flex fuel sensor, trying to maintain a tune while running this continuously variable fuel will be at the very least problematic, or at worst catastrophic.
https://cimg0.ibsrv.net/gimg/honda-t...c46dc8844e.jpg
https://cimg1.ibsrv.net/gimg/honda-t...8ea3f989cd.jpg

https://cimg9.ibsrv.net/gimg/honda-t...ada234535b.jpg


In the past, I have never paid attention to this or tested my E85. It's no wonder that I've constantly had to adjust my tune throughout the year. I plan on adding a flex fuel sensor this year so I know what I am dealing with, just sucks right now because I am about to fill up for the first drive of the year and knowing it will be class 4.

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

I would say a flex fuel sensor is really the only good way to do it. Unless you have your timing map conservative enough that it will be safe to as low as E50 (~96 octane), but you might still need to tweak fuel maps to accommodate.

Right now I just have a standard tube tester for calculating ethanol content. I will be testing it every time I fill up until I get my flex fuel sensor.

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Are they jacking with it now because it's been evolving for race purposes?

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Tough to say. The changes were kicked off back in 2016, but who knows how long it would take to fully implement. I am guessing it is to lower cost of production, since there are certainly different methods they can use achieve the desired vapor pressures without holding a minimum ethanol content. Probably different additives. Meanwhile, the cost of E85 has continuously risen along with the popularity of flex-fuel.

I'm sure the changes in ethanol content have little to no affect on factory flex-fuel vehicles, since they will run on anything from 0-85% ethanol or possibly even higher. It makes it almost impossible for people to run pump e85 without a sensor now. It all seems a little over-complicated though, why not just advise normal flex fuel vehicle owners to switch to regular gas in the winter if they have trouble starting their cars?

I will be interested to get some actual test results from different gas stations throughout the year to see what they are actually running. I imagine there may be some delay in when the pumps switch classes due to limited use of the fuel.

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

So I'm setting my car up for flex fuel and plan on tuning on both E85 and 93 pump gas, and having the flex fuel tables in Hondata set up. I'm no Hondata wizard, but it looks like Hondata will compensate the ignition and fuel tables based on ethanol content when using a flex fuel sensor, but what is one to do about boost? Someone please help me understand this.

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Safe operation REQUIRES a flex fuel sensor for E85. "Drops the mic"...

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

When I used to actually drive my car I would always pump at the same station (or try too) for consistencies sake. Never ran into too many issues but always had my laptop on hand. Flex fuel sensor would be so nice...

re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

I kinda thought it was already to standard to run a sensor if running E85. Seemed like one would sell themselves short by taking away the ability for the ecu to adjust on its own. Those sensors are mandatory on v8 E85 kits.

Re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

After filling up with e85 that measured around 70-75% ethanol in a test tube, I had to reduce overall fuel trim by 5% to get my tune back to where it should be. It is holding the same AFR as I had last fall which must have been on 80-85% ethanol.

From what I have read, ignition timing should not need to change at my power level when down on e70. I might get a little nervous if I went down to e50 and pull out a degree or so. But now I at least have a baseline for how much fuel I need to add/remove per % point of ethanol. :thumbup:

Re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Well I am on an outdated EMS system that does not support it so I'm SOL

Re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Even on previous versions of Hondata it was fairly complicated to set one up. You had to wire in a sensor, analyzer, and a resistor. There were a lot of things that could cause faulty readings.

I believe it has only been since the S300 V3 that it is truly plug and play.

Re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

I'm working through setting my car (S300v3) up for flex fuel, and I believe I will still have to wire in the sensor with a resistor, but the S300v3 can handle the job of the analyzer directly, meaning I won't have to buy one of those. I'm wiring my sensor output (with inline resistor) into AN0, and also plan on running the output (before the resistor) to an Innovate gauge.

Also, I just saw S-Manager updated to 2.6.8.0 and now includes boost compensation for flex fuel - sweet!

Re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

Whaaat?! =) That's a pretty awesome feature. Especially when I am running my injectors at over 90% DC at full boost, so when my fuel map shifts 5% I have to be careful not to max them out.

I should be setting up my flex sensor within the next couple weeks, just haven't had time with other priorities.

Here is the setup I am using, takes all of the wiring work out of it, including the resistor. For me, it's worth a little extra $$ to not have to mess with wiring :thumbup:

https://www.hamotorsports.com/ethano...r-harness.html
https://www.hamotorsports.com/ethano...nt-sensor.html

Re: Seasonal and Geographical Volatility Classes for E85 Handbook is available
 

If I upgrade its going to be stand alone