Ok, so I know that you shouldn't tune off of the millivolts because you could have a lazy or bad O2 and things could get ugly. However, I was wondering what the millivolts would read on a 03 Z06 for a 13-14 AFR?
It depends on the temperature of the sensor, and the values in the O2 Rich/Lean vs. Airflow tables. Basically the millivolt reading is telling you that you're richer or leaner than stoich. That's all a narrow band sensor knows. Get a wideband. Much cheaper than an engine rebuild.
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Best regards,
Bill
Calgary, Alberta, Canada
2003 Quicksilver roadster , 1SB, F55, QF5, MN6, Z06 Ti catback, 2 cat H-pipe & air lid, Euro red/amber tails, Vette Net, and HP Tuners s/w - available for free to anyone in Calgary
Generally speaking a voltage around .890-.900 will yield approximately an AFR of 12.8 to 12.9 --Larger numbers are richer--smaller numbers are leaner---an AFR of 13.0 would be about .880-.870--I never have tested one near 14.0 in fear of damaging the engine but I would guess that it would be near .840-.830
Here’s the table. But as you get to the extreme rich accuracy gets very poor.
AIR/FUEL RATIO-vs-VOLT READING
14.7/1- 0.50
14.6/1- 0.60
14.5/1- 0.70
14.2/1- 0.80
13.5/1- 0.85
13.2/1- 0.90
13.0/1- 0.92
12.5/1- 0.94
12.0/1- 0.95
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Alternative Fuels Vehicle Specialist
That data is useless without also stating a single temperature to correlate it with, like Bill said. Basically, a narrowband sensor is only good for identifying whether the engine is running rich or lean of stoich, nothing more. Attempting to determine exact AFR (off stoichiometry) from a narrowband is literally begging for broken parts.
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Greg Banish
Calibrated Success, Inc.
Here’s the table. But as you get to the extreme rich accuracy gets very poor.
AIR/FUEL RATIO-vs-VOLT READING
14.7/1- 0.50
14.6/1- 0.60
14.5/1- 0.70
14.2/1- 0.80
13.5/1- 0.85
13.2/1- 0.90
13.0/1- 0.92
12.5/1- 0.94
12.0/1- 0.95
I don't condone it, either, but that's fairly accurate. I was tuning many years before widebands were affordable, and this is about the same I've seen.
There's a good explanation here. But these two graphs pretty much tell the narrowband output vs temp story:
Continue tuning to something other than lambda=1 with a narrowband at your own risk, folks.
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Greg Banish
Calibrated Success, Inc.
In open loop, the computer is not taking data from the O2 sensors, just the MAF, MAP, ECT, IAT, TPS.
Pay attention.
He wanted to know a relative AFR to O2 voltage.
The oxygen sensor still outputs voltages relative to an AFR, even if it is in an open loop condition.
The difference when it is in Open loop or PE mode is that the VCM does not use the voltages for any adjustments, but they still output voltage, relative to some semblance of an AFR. That is exactly the asking gentlemen's point. I'm sure he's got the point by now that it's a better idea to use a wideband.
Corvette Store
Millivolts = AFR
