Understanding E85 A/F ratio to Gasoline?

[99cobra09]

I recently got tuned for E85 but i want to know if my A/F is accurate. I don't

have an E85 A/F ratio gauge, current one only reads gasoline. The current A/F

is at 11.5-11.8 at idle with E85, want to know what the readings would

be in gasoline numbers? If someone can explain how to convert those numbers.

I tried to search online but don't quite understand.

 

[03Steve]

What gauge are you using? Most widebands are lambda meters. Most wideband gauges display lambda on a gasoline scale.

 

[08 Z06 Dude]

Is your air/fuel meter a wideband? If so, what kind is it?

It is best to stop thinking about the mixture in terms of a ratio, and more in terms of lambda. If your meter has a reading for lambda start using and getting accustomed to it. The gauge only takes a specific output voltage from the wideband and turns it into a gauge reading.

Stoich for E85 is about 9.76:1, and gas is 14.65:1.

Stoich for E85 or gasoline will generate the same output voltage from the wideband to the gauge (lambda).

Therefore, if you are accustomed to reading gas AFRs, you can just pretend the car is still on gasoline and use the readings for your adjustments. Most of my gas buddies that converted to E85 have done just that.

**EDIT*** Doh! 03Steve said it in fewer words while I was typing...

 

[99cobra09]

Just checked the chart and lambada for 11.5 AFR is .790

 

[08 Z06 Dude]

Yes, you are 21% rich from the stoichiometric point right now. The cool thing about getting used to lamda is then the fuel used does not matter.

1 is stoich, less is rich, and more than 1 is lean.

 

[99cobra09]

^Thanks for the clarification.

I guess the A/F it isn't too bad at idle then.

 

[c6zhombre]

^Thanks for the clarification.

I guess the A/F it isn't too bad at idle then.

It's rich at idle.

Should be right around 1.00 lambda with a tight sweep (14.5 to 14.9 range on your gauge)

 

[08 Z06 Dude]

^^^ What he said. For E85 you should see a slight sweep with an average reading of 14.2 to 14.6 on a gasoline calibrated gauge.

 

[99cobra09]

Got to call the tuner to send me a tune with a leaner idle lambada.

 

[mystickb1996]

so what would it read at WOT? if tuned properly

 

[08 Z06 Dude]

so what would it read at WOT? if tuned properly

That depends on many factors like the amount of boost, static engine compression, IATs, and timing.

Ballpark, I would say between .75 and .8 lambda, which would be between 11.8:1 and 11.0:1 on his gasoline calibrated gauge, but actually 7.3:1 and 7.8:1 on a gauge calibrated for E85.

Getting E85 that is exactly E85 is very difficult, however; so this is another reason that using lambda instead of relying on ratios is much better.

 

[mystickb1996]

so its basically the same as a blower/turbo car with 93pump.. i have always tuned my blown cars around 11.3-11.5 wot on 93 with a cr on 10.1:1. i have been really considering changing to e85 so thats why im wondering

thanks for the info