ffueling

[meicalnissyen]

@Steve@VersaTune;

I was re reading the E85 section. A couple questions arise.
stoich for pure gasoline is 14.7
for E10, I believe, its 14.08

you say the PCM presumably uses 14.7 as its stoich value.
Given the ubiquitous nature of E10 in the US market, would they not use 14.08 for stoich ?

Sorry if this has been discussed in the past

[xfeejayx]

Originally Posted by meicalnissyen @Steve@VersaTune; I was re reading the E85 section. A couple questions arise. stoich for pure gasoline is 14.7 for E10, I believe, its 14.08 you say the PCM presumably uses 14.7 as its stoich value. Given the ubiquitous nature of E10 in the US market, would they not use 14.08 for stoich ? Sorry if this has been discussed in the past

1. E10 is common now, but car design is 10+ years old.
2. Trims can easily adjust for E10, it's like a 4% difference.
3. E10 isn't always E10, Mazda would be chasing their tail trying to accommodate it.
4. These aren't 1 market cars.

I expect they stuck with 14.7 just so it's a "known" or standard way of doing it, instead of adjusting for every change all the time.

For practical application, 14.7 vs. 14.08 as a base stoich number is irrelevant. You likely won't be checking the actual composition of your fuel every time you fill up, and that has an impact just like the "base" does. Get your tune right with whatever is in your tank, and let trims take it from there.

[Enki]

The ECU uses lambda for AFR measurement, then hits a lookup table to display logged data in gasoline AFR ranges.