AFR reading E0 vs E10

[JPMcGraw]

Suspend disbelief and assume we are in a perfect world only using the finest stuff here

Stoic for E0 is 14.7
Stoic for E10 is 14.1

Lets say i want to target 12.5 AFR on a stock bike. If i run E0 then i want my magically generic AFRometer to read 12.5:1. If i run E10 should I target closer to 12:1ish AFR because the stoichiometric ratio for Ethanol uses more fuel than Gasoline?

I realized i was tuning based on E0 and need to compensate for the far superior E10 but wanted to doublecheck i wasn't thinking in the wrong direction

 

[m in sc]

.6 isn't going to make much difference but it wont hurt to aim for a lower number (12.1). I bet you don't notice much a difference if at all. I'll be honest, ive never heard of anyone adjusting afrs for e10 vs ethanol free.

 

[dmonkey]

Your magically generic "AFRometer" doesn't know what fuel you're using. If it's using a wideband sensor then it reads lambda, and then it converts that to an AFR number that is based on what fuel it is configured to display a reading for. This means the AFR it displays is on a scale that is likely configured for lambda 1.0 = 14.7:1 AFR (unless you can change it). You could theoretically be running E85 and use your AFRometer to tune it on the E0 AFR scale, and people do that which gets confusing and is reason a lot of newer professionals tune based on lambda instead.

Resume your disbelief and consider that E10 at your fuel pump likely has the words "up to 10%" next to it in the USA. Actual content will vary.

 

[m in sc]

I thought about this a bit. 14.7 is the representation of the 02 sensor reading 1.0 lambda. so whatever the guage is designed to read, which is probably 'pure' fuel, when it says '14.7' it's actually saying '1.0 lamda' which is stoich regardless of whether its ethanol or not. so, I wouldn't tune for the offset. which is basically the same as ^