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Efi & e10

3451 Views 14 Replies 4 Participants Last post by  zwede
Ran across an article in the July/13 Hot Rod mag (pp 140-44) re: tuning EFI for E10 or E85. Being new to EFI (FAST EZ EFI just up and running) this was something I hadn't heard about before. I did a search of this forum but didn't turn anything up, so I thought I would put this out FYI and for comments.

HRM has a table showing adjusted A/F ratios for pure gas, E10 and E85. The also give a formula for converting one target A/F to a different fuel. In general they say to fatten up the target A/F for fuels with ethanol (no surprise, but I just assumed the computer already would do that).

pure gasoline stoichiometric 14.7
" " max power rich 12.5
" " " " lean 13.23

E10 stoichiometric 14.08
" max power rich 12
" " " lean 12.70

I can't get anything but E10 unless I buy race gas (not happening!) so I guess I will change my A/F targets somewhat.
What are you all doing, if anything?
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I havent changed mine but i dont run a fast or holley. Was on old tpi ecm now goin ls1 ecm. I was never in closed loop operation so i didnt need a target air fuel. I am hoping to go closed loop again with new ls1 ecm control but dont think i will change stoich because gas can vary. Gas contains up to 10% ethanol but doesnt mean it always has 10%. Station to station can be varied too

But it does make sense to compensate for the alcohol. But i target leaner than stoich for cruise anyway. Not too much leaner tho.
Don't change your target AFR!

You have a lambda sensor, it can't measure AFR (yes, even a wideband still only measures lambda). Stoich is always lambda 1, regardless of fuel. The wideband controller multiplies the lambda by 14.7 and shows you the number because we know what AFR is, but most of us don't know lambda.

E0, E10 or E85, stoich is still lambda 1. But it is presented to you as 14.7:1.

If you go from E0 to E10 or E85 you will have to richen the fuel map (inject more fuel), but your target AFR will stay the same since it is really a target lambda.
Yeah but doesnt the ez efi stuff self tune based on your air fuel ratio input table? I am not familiar with ez efi but if you setup the self tune table to target 12.8 to 1 for wot but dont tell it the fuel is E10, or E85 then its gonna look at 12.8/14.7 which is lambda .87 which is fine for gas but not fine for E85. Luckily E10 isnt too far off from normal gas, so what you command for gas will likely be ok for E10.

I was just under impression self tuning tables used afr tables and back calculated lambda based on fuel type stoich numbers. If so then perhaps you would want to change the ecm's stoich value to 14.2 for E10?
Ah nevermind i was thinking of my friends boosted motor who targeted .68-.75 or so for lambda on e85. I was thinking e85 liked more rich mixtures, perhaps it does but thats for you to find out. So leave your gasoline AFR meter calibrated as is and read it like if you were on gas. E10 isnt much difference so just find max power and whatever that air fuel ratio is you are set
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