Onboard AF ratio vs datalog fuel trims

[WhiTriCobra]

With my tune, I'll see my AF ratio at WOT do to a 11.4 and stay. My stft is a .98-.99 on both banks. Same as the ltft. So should it be a 11.4 or is is set for that rich in the tune so the trims will read to correspond to that? I was thinking maybe it's the 02's but then the trims look good. Appreciate it.

 

[oldbones]

With my tune, I'll see my AF ratio at WOT do to a 11.4 and stay. My stft is a .98-.99 on both banks. Same as the ltft. So should it be a 11.4 or is is set for that rich in the tune so the trims will read to correspond to that? I was thinking maybe it's the 02's but then the trims look good. Appreciate it.

Are you boosted?

 

[WhiTriCobra]

I have nitrous but that's a separate tune. This is the n/a tune. I can def see 11.4 for the nitrous or boost.

 

[oldbones]

Then your rich, my cars is about .86 lambda or about 12.6:1 AFR gas and 8.4:1 on E85.

It's your commanded AFR that is making it rich. Take it to a dyno and have them check your AFR if your worried that it is an 02 issue.

 

[WhiTriCobra]

I'll write my tuner again. My last tune would flux 11.2-11.4 at wot.

 

[heart_attack]

Isn't there something different about the coyotes a/f ratio? 14:1 is stoich instead of 14:7...or something like that.

 

[AKDMB]

Well, the dash goes off a 14.08 stoich AFAIK. The tune most definitely goes off a 14.08 stoich. 14.7 is for pure gas, we have e10 nationwide though. Look at measured lambda not, air fuel ratio, these cars work with lambda not air fuel ratio. You are never sure of the ethanol blend in your tank, could be e10, could be e15, e5, etc. you never know. Use lambda, it doesn't matter the stoich of the fuel. Datalog measured lambda and lambse. Lambse is commanded lambda, this will tell you what your tuner is shooting for. Most tuners seem to shoot for anywhere from .83 to .86 lambda. Most would shoot for the richer side I would say. 11.4 is indeed rich, going off a 14.08 stoich that would mean your tuner is commanding .81 lambda roughly. A fuel trim of .98 means the car is pulling 2% fuel to get to commanded lambda, just fine, 2% is dead on nuts. After confirming measured lambda is indeed this rich, you can consult your tuner and ask why the tune is so rich.

 

[WhiTriCobra]

Yeah I used the lambda and its where it needs to be. Def good to know. Appreciate it.