Atomic

iTrader: (42)

Take a look at the E85 worksheet I made in this section...thats exactly what it does. You put in how much e85 you added and how much gas was in the tank already and it gives you your new stoich afr. This is the only thing that needs to be change in the tune (the stoich afr value) since all the fuel tables are based on that value.

GMCtrk

iTrader: (27)

I dont agree with that. Ethanol likes to be richer at WOT than gas. Not that it's absolutely necessary, but just changing stoich AFR is not all that's necessary for an optimal setup. Startup parameters on e85 versus gas aren't remotely close.

Atomic

iTrader: (42)

Actually they both make best power around 0.75 lambda. The AFR will be "richer", but AFR becomes rather complicated when you start dealing with different fuels so I find it much easier to stick with lambda. I agree it will not be optimal, especially timing, but as far as fueling goes, it will be very close.

The flex fuel vehicles simply adjust the stoich value based on the sensor and a table in the pcm. Changing the stoich value does the same thing, just not automatically.

I am curious as to the startup fueling differences you referred to. Granted it is summer time so super cold starts are not really an issue right now, which is another reason why e85 in the winter is more like e70.

GMCtrk

iTrader: (27)

There's more to it than just adjusting the stoichiometric value. If you look at a FF tune you will see this. A non-FF operating system doesn't even have several of the ethanol related tables.

oakley6575

iTrader: (5)

I'm with KB here. I just want to be able to fill up with whatever I want and not have to worry about keeping track of what the mix was of the last tank and what the mix of the tank is on this fill up. Its pretty easy to add a couple degrees of timing at the track when needed. I don't need to be running an optimal tune on the street when I'm not drag racing

I contacted Bill over at HP Tuners but he wasn't any help at all. I'm wondering if there is a master enable/disable switch in the tune for flex fuel (or pin 56 in my case). You would think there would be a way in the tune to tell the pcm to start referencing pin 56 for the ethanol sensor input. Maybe I just need to add a pin there and it will reference it automatically...?

oakley6575

iTrader: (5)

Can you post a FF and a non-FF tune so we can see the difference. In my tune, I can see the stoich AFR table and the EQ (alcohol) table. What other tables are there?

LsF-150

iTrader: (2)

Did you ever make this work?

oakley6575

iTrader: (5)

I never bought a sensor to run but I am currently running E85. I find the E85 in my area is pretty consistant and there isn't any need to change the stoich value after each fill up. It does suck if I ever have to take the truck out of town but I haven't had to so far. I love E85 though. The truck runs really well on it.

GMCtrk

iTrader: (27)

I would freaking love being able to run the factory FF sensor. Unfortunately, there's no way to run it on 99-02 OS with a custom operating system in EFI live I believe it can be done in HP Tuners, but I'm not buying HP just for that.

LsF-150

iTrader: (2)

Been doing some reading and apparently in 06 they switched to the "virtual E85 sensor". My OS in my '06 has all the alcohol tables with populated values but my vin is a "T", I wonder if you had to have the "Z" vin for it to be turned on in the calibration? I think I'm gonna fill up with E85 in the next few days and see if it adjusts on its own or goes lean and trims way positive.