Can I use the rear o2 sensor input on my stock 03 evo8 ecu for a 0-5v wideband o2? What would be the proper equation in evoscan to show the voltage from the sensor? I can adjust it from there to correlate with the linear output of my wbo2.

Thanks in advance!

 

Any info on this?

 

I read my 0-5 wideband voltage through the rear O2. I just log the voltage "as is" and calculate AFR from there. It's another step, but it does work. After a certain amount of time (50 miles?), it will trip a check engine light, so I set up the wiring with quick connectors and someday I'd like to put in on a switch. After logging, switch back to narrowband rear O2, and voila! No codes tripped.
There might be a way to enter a formula that you can enter into evoscan and have it convert it for you, but I'm not that tech savy. Sorry.

 

On my car (Legnum VR-4) the rear o2 sensor input exists but is entirely un-used.. so it's safe to just use.. with evo turbolarry has a good first hand account above.

The real issue here is the accuracy of a 5V output.. if we calculate.. the PLX unit for example outputs AFR 10 - 20 using 0-5 volts.

So we have 256 values (8 bits) @ 13.8V.. that means 0-5V gives us 92.6 possible values..

10 / 92.6 = 0.107.. so in theory you can log AFR in roughly 0.1 AFR increments with just a straight 5V hook up.. which seems accurate enough to me.

 

I have my wideband set up to log through the ecu via the rear o2 pin. I had to use the rear o2 simulator patch in order to avoid the CEL.
Im using an AEM wideband and i have a formula that i use in evoscan to put out afr numbers.
I think i had to change 1 or 2 cells in the mut table also, cant really remember

 

I understand everything you stated just dont understand where you come up with the 13.8v base for 256 values then limiting it on the 0-5v. If you could expand on this I would appreciate it.

 

I think I might have been tired when I wrote that. It makes no sense, hah. I think I was thinking the input was a 13.8V input not a 5V input, which is incorrect.

It would seem the real answer is (for the PLX) AFR 10-20 is 0-5 volts, that particular input I believe is returned as 8 bit, thus you have 10 / 256 = ~0.04 AFR resolution.


What I actually went ahead and did is I am now making use of the native serial output of the PLX SM-AFR, and I wrote a .NET application to convert it the AEM serial protocol so that evoscan can read it directly. I then hooked up my MAP sensor (PLX SM-Vac/Boost) to the rear o2 input, so that I can log boost, as there is no other way to get that into evoscan and there is only 1 known spare analogue input on the Legnum ECU.