Rich AFR

[Neurotic Hapi Snak]

I have the AFR (commanded and measured) displayed on Torque when driving, and it displays the commanded AFR as 14.07:1 during closed loop. The measured AFR varying up to 14.07+/-.5. The only two examples I could find of AFR on a stock Yaris said it should be about 14.5-14.7. All I have currently is an AFE SRI, so pretty much stock. I live in Minnesota, so all gas is E10, an I was reading that stoich for E10 is 14.13, so this could be why my car runs a little rich. But it starts off at 14.07 right away, it doesn't start at 14.7 and adjust trim to 14.07. Does the Yaris have a sensor that senses ethanol content of the fuel? I've heard some cars have them, so the ECU adjusts for running on ethanol containing gas. Or is this something else? Anti-knock, but again, the car starts off at 14.07, it doesn't adjust to it.

[CTScott]

The Yaris does not have a fuel type sensor, so it is simply adjusting to the extra air from the AFE SRI. The flow difference between the stock intake and an aftermarket one is significant.

[Neurotic Hapi Snak]

But why would it change the AFR? The MAF would sense the increased airflow and the ECU would adjust the trim, but it shouldn't change the AFR, right?

[CTScott]

It may take a while for the trims to adjust to all that extra air. Unplugging the battery for a minute would reset the short term trims, which would make the adjustment occur more quickly.

[Neurotic Hapi Snak]

But I removed the negative battery lead when I installed the intake, and just recently I removed the battery to install an engine block heater. The intake has been installed for six months. Could the ECU store the adjustments for E10 and default to them? Because 14.07 is pretty close to the 14.13 stoich AFR for E10.

I'm trying to figure out if it's running rich because of something like E10 and not because of a problem. Maybe I should fill up with a non-ethanol containing gas and see if the AFR changes. Too bad summer's over, they sell non-oxy gas for boats around here. Maybe I could still find some, because I'm pretty sure 87, 89 and 91 octane all contain ethanol here.

[CTScott]

But I removed the negative battery lead when I installed the intake, and just recently I removed the battery to install an engine block heater. The intake has been installed for six months. Could the ECU store the adjustments for E10 and default to them? Because 14.07 is pretty close to the 14.13 stoich AFR for E10.

I'm trying to figure out if it's running rich because of something like E10 and not because of a problem. Maybe I should fill up with a non-ethanol containing gas and see if the AFR changes. Too bad summer's over, they sell non-oxy gas for boats around here. Maybe I could still find some, because I'm pretty sure 87, 89 and 91 octane all contain ethanol here.

We only get gas with 10% ethanol here as well.The Yaris definitely doesn't sense fuel type. I see 14.7 commanded in closed loop 99% of the time, with the exception of cold start, where it is 13.8. I watch it with my own YarGauge that I developed as a clock replacement device.

I actually wonder if Torque is doing the math incorrectly or has the 0 and the 7 somehow transposed.

[Neurotic Hapi Snak]

Could it be an anti-knock method? Run rich so it can keep optimum valve and ignition timing?

[CTScott]

Could it be an anti-knock method? Run rich so it can keep optimum valve and ignition timing?

No. For anti-knock the ECM just pulls timing.

[Neurotic Hapi Snak]

I figured out what it was, it was Torque. In my settings, I had set fuel type to E10, when I changed the fuel type to non-ethanol, the AFR changed to 14.69. Obviously the ECU doesn't read, or output through the OBDII, the exact AFR, just Lambda. So Torque translates Lambda based on fuel type in the settings, ~14.7 for non-eth, ~14.1 for E10.