Tuning LNF/E69 for E85 blends

[metroplex]

I couldn't find a setting for stoichiometric AFR for the Cobalt SS Turbo. I've seen stoich before on other GM files (newer vehicles mostly). This may sound like a stupid question, but how would I tune it for different E85 blends? Can I just let the ECU figure it out, and then scale the MAF based on STFT+LTFT data for each of the MAF frequency values (as if I was tuning it for a new intake or something)?

Or do I need to mess with injector settings? It seems more logical to adjust the MAF values based on STFT+LTFT because it'd run leaner with more E85 added to the fuel system. Any ideas?

[cobaltssoverbooster]

there is no stoich setting. you can only adjust the injector offset for the fuel you would be currently running. only the newer ecus with virtual ve have alcohol composition blending.

[metroplex]

What do I do with the injector offset? Adjust by the percentage needed to reach the stoich of the intended fuel blend? Do I keep the MAF settings the same?

What happens if I keep everything as-is and run say, E20 or E30?

[cobaltssoverbooster]

the value residing stock is your base gasoline value. if you run e85 multiply the value by 1.3 for a 30% fuel increase. if you run e60 or e40 start around 1.14 for a 14% increase in fuel.
i believe i have documentation on adjusting it but it the method is biased towards a tuners desired results. IIRC the links for it are in my signature.

[T-Man]

What do I do with the injector offset? Adjust by the percentage needed to reach the stoich of the intended fuel blend? Do I keep the MAF settings the same?

What happens if I keep everything as-is and run say, E20 or E30?

ECU reads fueling needs in the form of Lambda, no need to account for a different stoich value. As CSSOB stated, you want to try to shift fueling requirements based off of where your LTFT settles with the injector constant. Once you do your main shift with the constant value, you then fine tune with the MAF Frequency and MAF Correction tables.

[metroplex]

So which table/setting do I adjust (see attached) to account for different ethanol content?

On the Fords (Including my MPFI MAF Mustang GT), I can just change the Stoich scalar and keep everything else the same. With my 2014 SHO (speed density, GTDI), I can do the same thing as well. I noticed that the SE MI fuel must have more than 10% ethanol because my fuel trims are lean enough that it seems a stoich for E15 is more appropriate.

[Area47]

my advice, do not log ltft. pull the evap connector and run stft only.

[metroplex]

After reading this thread: https://www.hptuners.com/forum/showt...-for-LNF/page2

And looking at my screen shot above, it seems like here's what I need to do to run an E85 blend like E20-E30:

1). Adjust Injector Constant: Multiply by a factor to increase fuel (e.g. 1.08% for ~E30) so stock 0.02840 * 1.08 = 0.030672
2). Adjust MAF to fine tune it if necessary

Does that sound about right?

[MikeM173]

You might need to make more than one correction to the injector constant. It's just a good starting point.

You'll want to adjust the MAF to fully dial it in. You don't want to just rely on the constant. I'm sure you know this, but I mention it because you stated if necessary.

[cobaltssoverbooster]

make an initial adjustment and look at the global error on the maf sensor. if the whole thing is off by 5% make a 5% adjustment on the inj constant then tune the maf in completely.

this is the fastest way to get results.