Basic E85 conversion question

2000 Trans Am, naturally aspirated, 400ish hp
Car has 3 bar SD-RTT os still, from when it was a turbo car, although I do run a MAF now.

Assuming all else (as far as fuel supply) is setup to be compatible with E85...

Would I only need to change the stoichemetric setting from 14.67xxx to 9.76 and tune for that new AFR?

Will my stock O2 sensors work properly, or should I run open loop?

I have zero experience with E85. Not really having any luck finding definitive answers...especially when searching via a phone

You could only change the stoich to 9.76 if the fuel you ran was really E85 from a barrel and you tested it. Fuel from the gas stations pump is never really E85 and often varies from E50 to E80 this time of year. Here in Minnesota the best I've seen is E70 on my last fill up.

Yes the o2 sensors would still work. You would just have to go back over the MAF/VE for the change in fuel.

Running a alcohol sensor isn't possible on your 2000 operating system and that of course is the best option.

Thanks for the reply.
Not that it makes a difference, but my OS is a 2002 Silverado. I guess whenever that was done, it was easier since car is a 6.0/4L80E setup?

The E85 station that recently opened up just 4 miles away, has been testing anywhere from 84-90%.

From what I could find so far, some suggest starting with a 30% addition to your current VE settings and tune from there. Does that sound right?

The only OS that I know of that ran a real sensor on a P01 was like a tahoe/surburban OS from 2002.

If the fuel station has been testing good like that and if you wanted to get your own tester for cheap you may be fine with setting up the stoich at a set value. You'd be doing the best you can do with what you have anyway.

I don't know if 30% straight away is the right go at it, I'd just see what it wants first and make a global change with what you see. Then use your wideband error to dial it all back in.

I think I'm going to go for it.
I have access to chassis dyno so will do some street and idle tuning, then head there.

I'll cross the nitrous jetting part when I get to that point...using my VE percentage difference as a base for the nitrous tuning.

Thanks for replies.

I'm also considering using some flex fuel in my non-flex fuel 2008 5.3 Silverado.
It appears to have all of the tables populated in all of the flex fuel related sections, aside from it being disabled as a function.

From what I have read, the "virtual" sensor is not the best option, but I'm still debating (myself, lol) if it's worthwhile to even worry about it, as I'd mainly spike the tank when towing only, to hopefully eliminate any load related spark knock and let me get a bit more aggressive with the tune. This 2008 is much more finicky with timing than my 2002 ever was. I can't even run 87 otane like I could with that truck. Sucks being locked in with 93 octane, or having to take so much timing out it is a turd...

The sensor and pigtail is maybe $40, then wire it into the E38 computer and plumb it in at the fuel rail.

Then you'd have real flex fuel for your truck.

Changing stoich worked well for me, just made sure VE/MAF was dialed in. Once that's done you can follow your lambda error to see what the right stoich value should be. If you type in 9.7 and its running super rich make it a bit higher and see where you're at. Even your stock 02's are always looking for a stoich burn so you can follow them too if they're on.