E85 A/F ratio Question

[Tugger50H]

Just switched to Lund's flex fuel tune last week. After letting the car learn the fuel the a/f ratio has been be consistently 10.4 to 10.6. Filled up today at the same gas station and topped of my tank about 8 gallons of e85. Check my gauges on my way hope my a/f ratio was fairly steady at 9.2 to 9.6. Is this to lean?

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[Weather Man]

Rich, not lean.

 

[Tugger50H]

Still a little concerning why the sudden drop after a partial refuel at the same gas station.

 

[yellowstangatl]

You probably didn't have the same ethanol content in your tank. When I switch back to e85 it takes 2 fill ups or more to get back to the actual stations ethanol content. I monitor this with my ngauge, it also help to show when the content is learned by the PCM.

 

[beefcake]

Af is a measure of lambda. Stoich of e85 is different than fuel

 

[aschaefer]

Still a little concerning why the sudden drop after a partial refuel at the same gas station.

If you fill more than like 10% of the fuel tank capacity, the PCM has to relearn the ethanol content of the fuel so the tune runs a little rich for safety until it's adjusted.

At least, that's the way I understand it. Put ALCH_LEARN as one of your PID's monitored on your gauge, and you'll see when you fill up that it's a "0" and you'll run a little bit rich, then after a little bit of driving or a couple 2500 RPM holds, the car will learn the new ethanol content of the fuel and you'll see the ALCH_LEARN turn to "1". I even had mine set to display a red "0" and a green "1"

 

[FATHERFORD]

10.4 or 5 is something like 14-15 on 93 octane. Something like that.

 

[NBrock]

With a tank full of e85 mine reads in the low 9s. Perfectly normal with e85. Your alcohol content before probably wasn't as high. Either you still had a good bit of 93 in the tank or they got better quality e85 in.

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