The catalytic converter will change everything. That's why it's there. Some cats are more efficient than others. You have to measure before the cat and you have to use a wideband. The stock pre-cat O2 sensor is not accurate enough. Some will argue that it is a wideband but it is not linear and not a reliable reading. This has been discussed on here before.

 

When you say one point do you mean one decimal point like 12.9 to 12.8 or one whole point like 13.9 to 12.9?

 

Yeah I remember reading all that about the wideband. So where is a location they can measure it from? I have HFC's with an extra spot for a wideband sensor but it is still right after the cat.

 

Hmm, what if we have Cobb and measure A/F with that? I'm guessing Cobb reads off of the stock sensors meaning they aren't accurate either?

 

I've been told this
"The factory wideband oxygen sensors read approximately 1 point richer than actual Air/Fuel ratios in the richer regions."

 

in the richer regions would be below 12:1 or even less. The lowest you'll hit at 100% load / max rpm when tuned is probably 12.5:1 or so.

 

Drove back up to the tuner and did some data logging for a few hours this afternoon. Everything seemed ok in Cipher for the data log. The base map wasn't very lean at all to begin with and got really rich in the high rpm. The tuned map was showing around 12.7 all the way. We looked at ignition timing and messed around with it quite a bit, but the car just doesn't want to respond to it. I just don't know why there was such a difference on the other dyno last week. The dyno today was booked all afternoon so I'm going to have to drive back up there again tomorrow. Maybe this time we can get some better runs and get some nice consistent data.