lets talk wideband offsets.....

[0rion]

I screwed around with my wideband (LM-1) last week and messed up my offset. I set it back up and figured out what my offset should be only I'm noticing that it varies quite a bit from free air to car running. I can adjust the offset to have it on at free air but when I start the car I have to change the offset again to get it to match up. It's almost like it's not linear. Here's the real kicker.....I don't remember having this much trouble when I set it up the first time. It makes me wonder if I've been off for a while and didn't notice it. I watch the wideband itself so I'm pretty sure my tune is fine but as far as what hp has been saying I'm not sure of because I black box log all the time. I think I would've noticed if it were off by much but I'm not sure why it's suddenly off by so much.
I'm going to set up the offset again using a post at hptuners I found by sound engineer where he set the LM-1 to report a flat 14.7 ( 2.95v= 10afr and 2.95v=18afr) then adjusted his offset by that (using an average histogram for afr in hptuners). What I'm not sold on is the fact it'll be linear and if it's not linear how to adjust the offset accordingly.

[Frost]

There are things to keep in mind as well, such as the fact that the measuring equipment itself will produce error within +/- 0.1-0.2 AFR depending on conditions such as sensor temperature alone.

With that said, your offset needs to be found with the car running. Logic would seem to dictate other wise, but that's how it is if you want it nailed down as closely as possible. It's easier on the dyno since the AFR is just a ballpark and we are tuning for HP/TQ numbers, and don't really car to be at exactly some perfect single AFR number.

I use a similar method to force a constant output voltage, verify with good DMM, and log raw voltage to find % error.