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Efi & e10

3456 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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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.
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