Is Flex Fuel really needed if the E85 is always 85%?
 

I have an Ace B/250 coming in soon and have decided to switch from OFT to Ecutek to get more from the header. Seems like with Ecutek, you can have four maps. I'm thinking of having a 91oct map, an E85 map, and two maps inbetween to help transition (E70 when going from 91>E85, and E25 when going from E85>91).

I mainly just drive to work and stay around my area, live 2 miles from two E85 stations that always dispense 82-85% ethanol all year long, and I have two 5 gallon gas cans in case I need to carry some with me. So really, I'm going to either drive full 91 or E85 long term, the only time I won't is when I'm switching from one or the other. In a situation like this, is going Flex Fuel necessary?

it is much safer to have the flex fuel kit. There is a hell of a lot of ground between e70 and e25. And if you ever want to take a day trip or an actual drive, you might wish you had it.

we dont have e85 here in GCC but as i know is the e85 ethanol range is form e70 up to e90 .

There's no need for a flex kit in most cases. It mainly makes transitioning more convenient.

Your car can adjust of lets say about 30% of E content with fuel trims. But if you put in 93 on a e85 tune, the higher timing will make you knock. Along with running richer, your car will learn the knock and kill all your timing. To the point of limp mode or boom.

So no, e85 with a e85 tune is safe.
93 with a e85 tune is not!

The answer to your question is "it depends." Do you mix your own fuel and test it every time that you fillup? Then "no" you don't need a Flexfuel tune and can just use a dedicated tune for what you consistently run. If you only test it every fillup, what will you do if you suddenly don't have access to an E85 pump or the Ethanol percentage is way off?

It is a street car and if you ever take a road trip, you will want Flexfuel over a dedicated tune. A stock ECU might be able to adjust for mixtures containing E50 up to E95. Which can and does happen. Closed loop it doesn't matter since it can adjust fueling ±20%, or whatever Subie uses for a range of adjustment nowadays it might be different than what I remember, before triggering a CEL. But Open loop, high load or high RPM, still uses a fuel map that won't run as efficiently without adjusting the base map. This takes several fuel tanks to compensate for differences in fuel volume and density. I don't tune so I can't say for sure. But that's how I see it.

It is unfortunate that Flexfuel is so expensive in the aftermarket compared to just an aftermarket tune. Especially when it only costs the manufacturer a fraction of the cost for a fuel sensor, compliant hoses, and ECM adjustments. Stuff that they already use in other markets for other cars and can get cheaper than we can. But that would make every car more expensive for the few that use E85. :/ I'm just as happy to see options for Flexfuel kits nowadays.

You have a number of options


Best option is a full flex fuel kit/sensor and flex fuel tune fully automated put in whatever mix of petrol or E85 you like.
but cost is high


Next Best
4 map switch tune say 91/93/E40/E85. You need to be a bit more carefull with fueling and switch maps manually as needed, no flex sensor required




But you can get away with say an Openflash tablet (OFT) and a petrol and E85 tune stored on board and just flash back to petrol if you get stuck or going on road trip. no modifications needed at all other than tune
This is cheapest option usually.


E85 on stock car
http://www.ft86club.com/forums/showthread.php?t=67310

I guess my real question is, would I be wasting $600 on a Flex Fuel kit if I only run 85% E85? Technically, I'd no longer be using the "flex" features anymore.


From my one year of testing last year (ran E85 with OFT) and searching on old evo forums, socal always has 85% E85 all year long. As mentioned, I don't drive out of town and if I were to, I'd plan ahead to switch back to 91. During this transition, if I run to Empty (roughly 2.5 gallons left in the tank), I'd either be at E70 or E25.

Isn't OpenFlash going Flex Fuel pretty soon?

they're developing a kit for the turbo guys(sbd) so I'd be shocked if Shiv doesn't carry it over to the n/a guys.

Flex fuel really is the way to go, its just a lot more convenient.

I ran the oft with e85 tune for over a year, flashing back and forth between e85/91...never had one issue, but its nice to be able to just fill and go, not worry about mix etc.

You're absolutely right about the convenience factor. I was already leaning toward OFT for several obvious reasons. The attention to detail and constant updates/efforts from Shiv make for very confident spending.

So I've decided to just go with switchable maps for a few weeks to see how I like E85 + Ace header and if it's worth it. I didn't notice any difference when I used E85 + OFT lol. If I end up liking E85 + Ecutek (which apparently is more refined compared to OFT), I'll definitely get the Flex Fuel kit. So no more fun with hogging a lane and testing the fuel and getting dirty looks from the Propel station attendant anymore :)

Yeah, OFT is kickass and I enjoyed it while I had it. The constant updates are very very nice-much better than other platforms I've seen and used.

It'll be worth it. You didn't notice a big difference with e85? For me, I really only noticed it above 4k, felt like it pulled a lot harder. The ace header has been getting some pretty darn good reviews/posting good numbers-should be good.

If you didn't feel any difference, something might be wrong with the tune..? The Ecutek switchable maps will be fine for you, the E85 map should work anywhere from E70 & up. I've run it on E65 several times with no problems (no knocking, pinging, hesitation, etc).