Here is an example from today:
I'm using a wood burning stove to heat my house. The same Innovate MTX-L AFR gauge is used both with the stove and with alcohol and gas powered engines.
- The Innovate MTX-L doesn't know it's reading the exhaust gases from burning wood, all it cares about is the contents of the gases in the exhaust. When it measures Lambda=1, all is well, doesn't matter if you are burning wood, ethanol, gas, nitro or whatever.

Why make things complicated with AFR?

I don't need to know the stoichiometric value for burning wood, I don't need to know it for ethanol, I don't need to know it for gas...all I care about is Lambda, and that's what the AFR gauges with oxygen sensors are measuring. If interested, one (or the gauge) can then compute the AFR...

With an Innovate or some others that's correct, however if his O2 system is set for typical gas stoich at 14.7 your table has no value. Sensor calibration is done in free air, however the gauge calibrations if set and unchangeable at 14.7 (equaling a 1.0 Lambda) will suggest a starting point reading around 12.2 to 12.5, which translates to .83 to .85 Lambda. Those are safe starting numbers, jet from there as needed for best performance.

I agree the 12.2 can be used as a starting point, but with E50 it will be lean, and even more so with 12.5.

As far as I can see the table I published is correct:
- Stoich for E100 = 9.0
- Stoich for pure gasoline (E0) is 14.7

With a 50% mix (E50) the stoich (Lambda=1) will be (14.7-0.5(14.7-9)=11.85, shown as 11.9 in the table.

For max performance with E50 we aim at Lambda = 0.85, which gives us roughly AFR = 10.1 with E50, shown as 10.2 in the table (Lambda target unknown for WOT in the table).

So in my opinion the table is correct, and an AFR gauge set to stoich 14.7 for pure gasoline, should display AFR = 10.1 for max power at WOT with an E50 mix. For ideal combustion (Lambda = 1) it should show AFR = 11.9

The table is correct, however... it would only show an AFR = 11.9 at stoich if the meter can be rescaled to represent E50. Mark is assuming the meter can only read on the gasoline scale. If it is, the meter is going to be reading 14.7 at stoich regardless of what fuel you're using if you do not have the ability to adjust the AFR scale.

Especially with an oddball fuel like E50, I would suggest buying a meter that can be set to lambda, it'll be much easier to comprehend instead of trying to back calculate AFR targets when it's not displaying the correct scale.

Correct, his gauge can't read Lambda, so the assumption that it is fixed at 14.7. With E50 it should actually run leaner than with E85, the higher percentage of gas will need less fuel. Straight gas will be anywhere from 12.8 to 13.2 depending on vaporization properties of the gas and the distribution ability of the engine. A very efficient engine can even run well up into the high 13 range. 12.5 will be more than safe with E50, what it wants in the end is up to the engine. The AFR in the 10 range will only work if the gauge can be calibrated to register a stoich value of 11.9.

Yes, you are right, I (finally) see the point with the non-programmable scale...