[Conner0388]

So I’m trying to find the difference between getting a flex fuel kit or just getting a tune for 93 then a tune for e85. I think with the flex fuel kit will allow me to use a mix between 93 and e85. What are the negative of just getting a tune for 93 and a separate one for e85 without the flex fuel kit.

[Conner0388]

Or do they do just a flex tune without the kit?

[arpad_m]

Originally Posted by Conner0388

So I’m trying to find the difference between getting a flex fuel kit or just getting a tune for 93 then a tune for e85. I think with the flex fuel kit will allow me to use a mix between 93 and e85. What are the negative of just getting a tune for 93 and a separate one for e85 without the flex fuel kit.

The big huge negative is that you have to keep the ethanol level constant, because without the flex fuel kit the car won't be able to measure E content and adjust stoich, thus you have to "bake in" a fixed E percentage into the tune and get exactly that (or only 93) every time you fill up. If you don't deplete the tank completely each time, you will inadvertently blend your fuels.

Massive PITA and risk just to save $450 or so, I don't think it's worth it.

[FlukeSS]

Originally Posted by arpad_m

The big huge negative is that you have to keep the ethanol level constant, because without the flex fuel kit the car won't be able to measure E content and adjust stoich, thus you have to "bake in" a fixed E percentage into the tune and get exactly that (or only 93) every time you fill up. If you don't deplete the tank completely each time, you will inadvertently blend your fuels.

Massive PITA and risk just to save $450 or so, I don't think it's worth it.

This gai gets it ^

Flex fuel myself. Not ready to dedicate the car to a fixed tune point regarding fuel mixtures. Its different if it was a dedicated track/drag car. Then I would consider it.

[BruceWayne1LE]

I can’t even think of any benefits of tuning your car to 1 fuel. It’s a no brainer to get flex fuel.

[WillyZ83]

I did the flex fuel kit and glad I did. Spend the money and get it tuned properly.

[TP2SS]

I've given up on getting a flex fuel system. $350 or so for the kit (not bad) but you can't find anyone to give you the tune without doing a $700+ dyno session. Totally unnecessary if you have NO OTHER mods. GM sells thousands of cars with flex fuel ECUs with no dyno-ing of each one. But apparently there's no "standard" flex fuel tune that can be loaded remotely. I've contacted a few tuners asking why they can't, don't, or won't have a standard flex tune for no-mod cars and they all say yada, yada, yada about they need the car there for whatever. When I point out to them the reasoning I list above...crickets.
Not going to spend $1000+ just to get flex fuel capability on a car I'm never going to mod beyond that to save a few bucks on a fillup or get a few more HP from!