E85 AFR table

[Kranked]

Hi all,
I have a question about E85 AFR table.
The gasoline stoichiometric is 14.7 max power rich is 12.5 and max power lean is 13.23.
E85 stoichiometric is 9.765, max power rich is 6.975 and max power lean is 8.4687.

So, what AFR values should I use @ cruise and WOT with E85?
If I want max power then 14,7/9,765*6,975 = 10.5 so I can use 10.5 value @ full throttle?

Thanks!

[Matt Cramer]

Widebands normally think in lambda; you might want to switch to using lambda values, or use "gasoline equivalent" AFR ratios. The latter would be what you'd wind up with if you use the default calibration. For example, an LC-1 would deliver 2.5 volts at stoichiometric if you set it to its defaults, no matter what that fuel is. So if you do not change your lambda sensor calibration settings, TunerStudio would show you 14.7:1 when you're really at 9.765:1.

[Kranked]

Thank you for the answer!
In that case which is the best AFR ratio to cruise? I think with gasoline the value is between 15-15.7 but if I set my AFR table to this value it will be good with E85?
In full throttle I need to use the gasoline best power AFR value (12.5) or the E85 value (10.5) in my AFR table? So, if I write 12.5 to my AFR table it means 10.5 AFR with E85?

Or?

[Matt Cramer]

It's easiest to just use the gas values.

[jmaz87]

to avoid starting another thread I'm replying to this one.

I have been thinking about switching to e85 for a while since i sell it at my station

I was told I could switch fuels without making any setting changes (using gas values) and all i need to do is re-tune VE to get back to target AFR table's values now on e85

is this correct?

later i can have both maps tune and blend but i wanted to make sure this would work TIA

[dcg9381]

I don't quite understand the question..
You indicated that you could make "no changes" other than re-tune the VEs.

Retuning the VEs is a change..

Practically speaking from someone who has made this change at the pump.. The first time I tried it, I nearly pooped myself. I added a tank of E85, increased my req_fuel value about 25% and restarted.. It immediately died.... And I thought I was stuck.

I found that I had to do two things:
1) Adjust that req_fuel value
2) Retune the VE table.

AFR table can remain the same (see above). You'll end up with two tunes. I never had any problems with transition fueling when filling up at or less than 1/4 tank.

You can do it without any changes -there is some sort of E-85 detecting gismo that can adjust your fuel values, but never tried it.

[jmaz87]

I guess I was a little confused at the time

but now I get what Matt and others have mentioned. since Lambda shows the same voltage @ stoich regardless of fuel, the calibration (target afr) can be left alone, and the values regfuel and VE would be altered as needed.

I think i got confused because ideally your target AFR table could be a little leaner even though you are actually using more fuel, maybe I didn't take req fuel into consideration...

with that said does anyone know what an ideal table would look like for example 12.5:1 for gasoline and I've heard you can go several points leaner on e85 without issue, does anybody agree? keeping a close eye on knock and egt that is

[dcg9381]

I haven't tried going leaner. Just be aware that AFR targets are not going to allow you to start up.. You're going to be 20-30% lean across your fuel map and depending on AFR targets, even with high EGO correction probably won't work very well - might limp you home, but probably not. It'll be dying too lean before the 02 can correct.

[jmaz87]

my shop sells e85 and I still haven't tried it because I want to run a flex sensor to tune in correction i.e. ill know whats in my tank while i tune so i can compensate for future mixtures

if i was gonna just dump e85 into my empty tank, i'd probaly add at least 20% to req fuel and maybe an additional 10% to the entire VE map just to have something to start with before tuning. does that sound acceptable?

ideally i'd get some e100 and tune one map with that and the other with premium so my flex sensor can blend the two on the fly

[dcg9381]

Yea, something like that.. Just expect to have to re-tune fuel to start up. I think I did it with req_fuel in general... That was enough for me to put-put away from the pump.
It took a surprising amount of fuel.

Turbos love E85 though..