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[NoPistons!]

well i know what afr's to shoot for when tuning a turbo car...so i thought.  Most gas pumps have 10 percent ethanol in their premium blends and finding this out caused me to facepalm then make this thread.

E10 stoich afr is 14.12-14.2
E85 stoich afr is 9.75 (please correct if wrong)
and the old unleaded afr is 14.7

If your ecu has a stoich afr setting please be aware of this. 

[Phate]

well i know what afr's to shoot for when tuning a turbo car...so i thought.  Most gas pumps have 10 percent ethanol in their premium blends and finding this out caused me to facepalm then make this thread.

E10 stoich afr is 14.12-14.2
E85 stoich afr is 9.75 (please correct if wrong)
and the old unleaded afr is 14.7

If your ecu has a stoich afr setting please be aware of this.

Don't most O2 sensors just read lambda, and then scale the output for gasoline?  I remember reading something about not re-calibrating a wideband when tuning for E85, since its lambda output is the same at stoich, regardless of the fuel.

Before I say more and look like too much of a dumbass, I'll wait for someone else to come in and drop some uncontrollable knowledgabilities.

[PhilStubbs]

I tune the same with e10 as I did with non ethanol gas. I have yet to blow an engine in 7-8 years.

[92CXyD]

I tune the same with e10 as I did with non ethanol gas. I have yet to blow an engine in 7-8 years.

So do I since almost every gas station I've been too has 10% or less ethanol in the gasoline, since it is federally mandated for the last 5 years. 

[Joseph Davis]

10% ethanol blended gasoline is 14.09 AFR.  E10 gasolines will be stoich at 14.09-14.7 AFR.

Using a display calibrated for gasoline, 12:1 on gasoline, 11.5:1 on E85 (stiffer alcohol blends) and you will be fine.

[NoPistons!]

I have to run a bit on the rich side anyway having batch fired high impedance injectors and all but i'm glad it doesn't make much of a difference.   Not overly paranoid about it.  Just something i was curious about.  Mind at ease.  Thanks. 

[92CXyD]

10% ethanol blended gasoline is 14.09 AFR.  E10 gasolines will be stoich at 14.09-14.7 AFR.

I've been tuning as 14.5:1 for stoichiometry and been good to me. 

[HiProfile]

Lambda is the current AFR divided by stoich AFR, found by reading how much oxygen was left unburnt. A stoich AFR for methanol will be 1.0, a stoich for E0 gasoline is 1.0, and stoich for E85 will be 1.0. You could even check the lambda of charcoal with your wideband (in theory). AFR's are what are different.

If you want methanol to be 15% rich, which is an AFR of 5.27 (6.2 is stoich), you take that lambda value (5.27/6.2=0.85) and multiply it against what your wideband readout is set to. In most cases it's E0 gasoline, which is 14.7: 14.7 x 0.85 = 12.5:1 ratio.


The fact is every motor & wideband controller will be a bit different, and each sensor will have a certain amount of aging on it. Find what makes the most power (safely) for the combo you have and you'll be set.

[Joseph Davis]

10% ethanol blended gasoline is 14.09 AFR.  E10 gasolines will be stoich at 14.09-14.7 AFR.

I've been tuning as 14.5:1 for stoichiometry and been good to me. 

Since you use an AFR display meant for pure gasoline, and not a lambda meter, this is not stoich.

[92CXyD]

10% ethanol blended gasoline is 14.09 AFR.  E10 gasolines will be stoich at 14.09-14.7 AFR.

I've been tuning as 14.5:1 for stoichiometry and been good to me. 

Since you use an AFR display meant for pure gasoline, and not a lambda meter, this is not stoich.

Yeah I know, I'll change that closer 14.09:1 on the next Crome map I do on my son's 1g Teg w/ 3stage vtec D16 

[ratcityrex]

Fuck stoich!  I'm going for mpg not emissions. ...