E85: E70, E74, E80...changing pump mixture a problem for tuning?

[scheides]

So through the seasons at the pump E85 is offered in various flavors. In the summer it's full 85% ethanol, and in the winter it's 70%. This then means that the target AFR will vary between 9.7:1 to 10.5x (?) as the various seasons come and go. I'm considering switching my evo over to E85, and I know it's possible to re-tune the stock ECU to run efficiently on E85 w/ ECUFlash or AEM (which the car will eventually get).

The issue I see is this change in mixture through the seasons. I don't think it's a small enough change to 'not really matter' in a car like an Evo, where I'll get it tuned for high boost and strong timing. Will a re-tune be needed for each new season's mixture? Or is it really close enough that it won't matter?

Call me a tree hugger, but the simple fact is that E85 is produced locally and was made for a turbocharged application, and I'm considering giving it a go.

[rst95eclipse]

Tree hugger. I'll be doing the same and the concensus out there is that you'll need to have it tuned every season or find a way to have a consistant blend of ethanol. I haven't done any research on how to test the blend or where to find E100. Not that I'm asking you to do it for me, but if you do research this a bit more, please post your findings. I'm just not at the stage to be thinking about tuning - not even close.

[Halon]

That is one of the downfalls of E85, is that it goes through I believe 4 different blends over the course of a year. Some people seem to be buying barrels of E98 and just running that since it has a higher ethanol content, and a steady mixture. I'd really like to be able to test what is coming out of the pump though. Maybe I'd buy a barrel of E98, and if I could just test the mix coming out of the tank, and add a little E98 to the tank if the E85 is on the lower mix to bring it back up to the 85%. But as of now, I haven't found a quick and easy way to test it.

[scheides]

See this is the problem with a good idea like E85, they go and screw it up like this...yet still, the rest of regular gas receives up to 10% ethanol through the winter and it doesn't seem to bother anyone?

The only thing I can think of is to get tuned for E70 and then as you pump in the various other mixtures you will simply be running richer. This would theoretically be more safe than getting tuned for E85 and then running that tune on E70.

[Halon]

Not sure how well that'd work. I see what you're thinking, because the 85% mix would probably perform better, so you'd tune it on the weaker 70% mix and just use that even when it goes up to an 85% mix. But remember that when going from 70% up to 85%, you will need to actually add more fuel because of the higher ethanol content.

My plan is to get a dyno tune done early spring on the weaker mix. By summertime I should have a wideband installed in the car. I will have to just monitor the wideband readings, and make minor changes from the original tune over the course of the season when I start noticing changes.

[Halon]

BTW, I'm ready for E85 now! I just got my 1600cc injectors last night. I should be good to go yeehaw!

[JET]

Mn gas is E10 all the time, not just in the winter. E85 has issues starting and warming up in the winter, that is why they drop it down to E70 in the winter. I have seen the dates posted of when it changes, but I would like to know how strict that is.

[Halon]

Ya, and even if they change at a certain date, I usually don't see too many cars filling up at the station on E85. So even if they switch to 85% say, March 1st, They probably still have a tons of the 70% in the underground tanks. So 85% may not even be coming out of the tip of the gun until April for all we know.

But could you post up those dates?

[AJ]

Buy a drum of E98, get a heater for the block in the winter, tune it for one flavor of gas, and call it done.

[Shane@DBPerformance]

You have to look at more than the A/F ratio, if you are going to try to push the car on E85. Tuning it on the worst/lowest ethanol mix and then just richening it up later when it has more ethanol in it should work ok. Tuning it on the best mix and then later just trying to fix the A/F ratio might not work so great, since you will be losing some of your cooling and knock resistance.

You can't get E100, because that would be a drinkable alcohol. They add 2% of whatever(gasoline, methanol, poo) to make it into E98, kinda of like what they do with automotive nitrous to keep you from having too much fun with it. People who are using E85 as a legal racing fuel are mixing their own and using racegas for the gas portion.

Yea, normal MN gas is the same year round with 10% ethanol, so you don't have to worry about it changing too much.

There is a simple way to test the ethanol content in gas using a graduated cylinder and a little water.

"The ethanol and gasoline levels used in producing E85 will vary by season and from region to region. Minnesota, because of its location in the northern United States, may have an ethanol content of 70 vol% in April, while Texas may have a (minimum) content of 79 vol% during the same month. The E85 blends in Minnesota will vary from a minimum of 70 vol% in winter to a minimum 79 vol% ethanol in summer. The following blending ratios (Table 1) should be used for ethanol blending in the northern tier of the United States. "

"As is the case with petroleum-based fuels and their respective engine technologies, seasonal blend adjustments are required for E85 to ensure proper starting and operation in FFVs. ASTM 5798-98A has been adopted to provide blenders the specifications needed for formulating E85.

Early fall changes are of particular importance to prevent cold weather starting problems. When supplying E85 to retail outlets, the date and the expected sales volumes of each station should be considered when determining what blend to deliver. An E85 station should NOT carry over a summer blend into fall or a fall blend into winter months. E85 blends, contrary to a popular misconception, have relatively low vapor pressure (tendency to evaporate), and a higher petroleum content is used to bring E85 vapor pressure into line with colder weather starting requirements. Adjustments may be easily achieved by adding gasoline to the existing fuel in the storage tank for the cold weather target blend. "


Season Months Blend (minimum ethanol content)

Spring March, April, May 74 vol%
Summer June, July, August 79 vol%
Fall September, October, November 74 vol%
Winter December, January, February 70 vol%