Ethanol AFR's

[mcleansc]

Apologies if this is an incredibly daft question, patience is requested

I'm running an E40 mix (no flex fuel). Me being from Scotland E85 and Ethanol was never really a thing so it's my first time using it. I want to be able to read my fuelling when data logging and wanted something cleared up.

On my last WOT (3rd gear) MHD read AFR's of 12.0. I've been on a deep dive today trying to answer this. Am I correct in saying the O2 sensors read in lambda, and convert that lambda reading to a gasoline output? If so, would I need to do the following to get the actual AFR when using E40:

- A reading of 12 for gas is a lambda of 0.8163 (12/14.7). So the sensor is reading a lambda of 0.8163 then converting it to gas on MHD(?)

- E40 stoic is: 12.4 and 10.7 for WOT (according to the internet, which we know is never wrong )

- That's means if the O2 sensors are reading a lambda of 0.8163 and giving a gas output of 12 on the gauge, then for the E40 AFR I need to take the sensors lambda reading of 0.8163 and multiply the E40 stoic of 12.4 by it to get my my correct reading, which is 10.1?

Or am I overthinking this / don't actually understand what I'm talking about?

 

[mcleansc]

Anyone able to shed any light on this? I've been reading more on O2 sensors today.

From what I gather the O2 sensor compares the O2 level in the exhaust to ambient air and using voltage changes in the sensor it can tell if there's too much or little air in the exhaust gases? 450mv is 'stoich' which is a lambda of 1. Less than 450mv means there's too much O2 in the exhaust gases (running lean) and opposite for above 450mv and running rich.

So the 'AFR' reading we get has nothing to actually do with what the sensor is registering? The sensor is just taking the voltage changes as lambda then using reference tables for the fuel it's configured for (E0, E85 etc) to convert that reading to what it believes the air to fuel ratio in the cylinder is?

So for example if it's reading 450mv, which is a lambda of 1, and it's configured for E0, it'll read an AFR of 14.7:1.
However, if you have E85 in the tank, it's configured for E0, but the voltage is still reading a lambda of 1 (450mv) at the sensor, it'll still display 14.7:1 despite the fact the actual AFR is 9.7:1, which is stoich for E85? And that's because it's configured for E0, and a lambda of 1 in the exhaust gases equates to an AFR of 14.7:1 in the reference tables?

If this is accurate my next question is can/does MHD change the reference tables when you install an E20 or E40 map, so the AFR you are reading on your 'gauges' in MHD is for E20 or E40, or is it still configured for E0 and you need to convert it?