kbracing96

iTrader: (26)

Actually, I think it will work just fine, since there is no longer a fuel composition sensor. Its all done with the tune now. The fuel trims are now what it uses to calculate how much ethanol is in the fuel and adjust stoich accordingly. If you load up a FF tune, and have the fuel system to support it, I see no reason why the the PCM can not adjust to the different mixes. Have you looked at the later model tunes with FF to see how they are setup? I believe it would work. I would not be afraid to try it if I had a late model truck, but I have EFILive too...

BTW, from my experience, even if you put E85 in a non-FF vehicle, it generally will not hurt it, it will most likely just max out the fuel trims and throw a lean code. I have seen this happen and it didn't do any harm to the vehical.

nighthawk08

I have enabled the flex fuel option in hp tuners and the vehicle went into some crazy limp mode and wouldn't go over 10-15 mph. and also there is a scanner function for fuel composition and it never moved off 0 even when the flex fuel was enabled in the ECM.

kbracing96

iTrader: (26)

Did you put a FF tune in the truck and have E85 in the tank? Like I said earlier, trucks that didn't come FF, don't have all the FF tables filled in correctly for E85, they are filled in with the same values for gas. I would suspect that is why it when into limp, cuz it was getting conflicting information.

nighthawk08

in my file, everything is filled in correctly. the "alchohol" tables all have different parameters. I know this because when I run e85 I copy all those tables to the gas tables.

if you compare a 2008 truck file...FF vs non FF the only difference is one has the FF option turned on and one has it turned off.

outdooricon

This is some great dialogue!

So, I'm confused then.... If you're saying that changing the tables won't let you run both but the new generation doesn't have a sensor, then what else would the FF trucks have that would allow them to run whatever they wanted??

nighthawk08

I really have no idea.

outdooricon

I wonder if it may be that since you have a 4.8 that you're seeing a different scenario. Maybe it's possible there's code in the PCM that doesn't get run for 4.8's that does get run for 5.3's and that's how it may be able to handle both once the tables are updated...

95 bright teal

Kyle was running flex fuel when he had his 4.8, so no...

outdooricon

He was able to switch between E85 and regular whenever he wanted, without any problems?

kbracing96

iTrader: (26)

I tuned for it, which was quite easy, just adjusted the stoich table till my short term fuel trims where around +/- 3-4% since the rest of the tune was already dialed in. I added a little timing too.