What's the conversion from the sotck O2 sensor voltage to the AFR number? Not using it for tuning, just trying to see about where I'm at.

 

I thought I posted this a year or two ago. Compiled many datalogs and put out an excel spreadsheet graphing the stock O2 vs the wideband. Can't find the spreadsheet so I must have killed it. Can say that there is one helluva spread on the NB output meaning that a narrow volt range equals a large AFR range.

 

Man, I searched for that post for 10 minutes and couldn't find it, thanks though.

Anyone else?

 

I think the stock sensor is more of a switch, between lean and rich.
Above certain voltage its rich, below certain voltage its lean. How much lean and reach is not accurate.

You can see from this graph:

 

I searched for it as well but I think it's gone.

What I recall is a wide range of AFRs for each nb voltage. xyz volts on nb was equivalent to a wide range of afrs so you could never really know where you were. There was a voltage however where my nb would equal a 10-11.2 or 10-11.5 afr range, just cannot remember. Plus your nb may act different than mine did.

 

yeah, I was hoping someone had the equation for the stock NB or had plotted one against a WB on the same run so you derive the NBs AFRs.

 

There is no equation. Below 14.7:1 is about 1 V, Above 14.7:1 is about 0V. There is a very quick transition between 1V and 0V at 14.7:1, just like in Reza's graph. This is precisely why the stock ecu relies on fuel maps under boost and why an A/F reading from the stock o2 sensor is worthless.

 

Well, according to the datalog file, the O2 sensor never read more than 1.03 on the run I stored. That seems lean since it's awefully close to stoichiometric, but according to that graph Reza posted, the jump between 1.0 and 1.02 could be a huge difference in AFRs. I just wanted to get an idea of where I'm at. I was worried I might be running lean since the car hasn't been tuned after all the bolt-ons. I'm still worried since I have no idea what AFR 1.03 is, but who cares, I'm taking my car in for a new motor in 2 weeks anyways. I can get Rick to tune it then.

 

Exactly!

The stock o2 sensor will read 1V from 14.7:1 to 0:1. You have no idea what the A/F is within that range. That is why you cannot tune or even monitor with the stock o2 sensor.

 

Is there a way to make the PFC read voltage outputs from a 4 wire o2 sensor? Then you could tag different voltage levels as different afr's. And use it to tune in car while monitoring o2 voltage. That would eliminate the need for an in car mounted WB....if you could decipher the voltages, that is.

 

A 4-wire sensor is not a wideband.

You can get a Techedge wideband for $3XX that works great. ANY wideband o2 sensor will require a separate controller.