Looking for some estimates / best guesses on when E70 will arrive in the Chicago / Wisconsin area, AND whether I will need a retune for this. I would like to do an E85 re-dyno anyway, but am wondering if I should have my tuner make an additional E70 map for the winter. I would rather not, if I could safely avoid it, so that's where I need your opinions.

I haven't been able to source a GM sensor from a local junkyard yet, but I'm goingf to keep looking before I shell out big bucks for aftermarket. At least once that's hooked up I'll have a little more peace of mind about what E content I'm getting. PS this is for my evoX.

 

Ethanol "regions" are defined by the U.S. Dept. of Energy. Check the Handbook for Storing and Handling E85; in appendix A, you'll see a listing of Geographical Fuel-Marketing Regions. Northern Illinois gets class 3 E85 in the winter, switching to class 2 in April, and switching to class 1 in June, then back to 2 in September, then back to 3 in October.

Classes are described on page 11. Class 3 is a minimum of 70% ethanol, class 2 is minimum 74%, and class 1 is minimum 79%.

(Notice how the minimum is never actually 85%, no matter where you are in the country? Only in America could we market a product with 70% ethanol content in it as "E-85".)

 

So if I retune for minimum 70%, won't I go lean when we get 85% stuff?

If I tune for 85%, then will it knock at WOT with 70%?

Wondering if I need two maps, or just not worry about it.

 

if you were tuned really really aggressive on "Real" e-85(we have e85 but with a 85-88% ethanol content all year round) like we can get here in sd, then you might be slightly rich going to regular e-70 winter gas. won't harm it, but won't make 1200whp either. You should be ok with out a retune in the winter =)

 

So is it better to tune on the highest E-content, tune on the lowest E content, or just try to go middle of the road?

 

This is why ethanol sensors are used. To be as safe as possible you should at least have a summer and winter map. Based off of what your ethanol content sensor reads... pick the better suited map. The lower the ethanol content, the richer the a/f ratio and lower octane rating will be .

 

Yeah, that's what my instinct told me too. Got my used E content sensor on it's way here . It's still nice to know that it probably won't blow up if i mix up E70 and E85.

 

Just some data.

About 4-5 months ago the local station had some issue and the E85 ended up only being about E55 or so. Other than the fuel trims getting totally wack, the car ran more than 1 full point richer.

I datalogged a bunch of WOT pulls and there was zero knock, the car was just a bit slower and less responsive because of it being so rich. This was on my personal Evo which I tune a far bit more aggressive then customers.

I'm not saying your car will be ok but I think E85 to E70 is not such a drastic change as some people think, it's still 70% Ethanol. Espically since it's most likely not true 85% to begin with in the summer months.

 

So that said, is it even worth it to run an E-content sensor in your opinion?

 

I put one in mine to just make sure what was flowing through the lines, not just for the summer and winter months, but I have a dual map switch so I make sure the map switch is correct. I used my zeitronix sensor to control a little logic board, if the e content is under 30% than it switches to the 93 oct map, if it is above 70% than it uses the e85 map. I just did it automated so if someone else is driving the car, like my dad, they can fill it up with whatever they want, e85 or 93. BUT you must make sure the tank is almost empty if you are switching from e85 to 93, don't want to end up in that 50% no mans land on the ethanol sensor gauge...

 

Yeah, with no retune, I see same power and no knock with E85 and E70.

 

Hmmm.... anyone interested in a GM ethanol content sensor?

 

You'll probably want to verify for yourself the ability to run the same tune using either E70 or E85.