I'm trying to determine if my W/B sensor might be starting to go or I'm just seeing higher AFRs because of the warmer temperatures.

Observations and information:
I'm running a Cobb w/ stage 2 AEM intake OTS map. AEM intake, CBE w/ test pipe, stock DP, UICP, LCIP, stock bov, stock fuel injectors and pump. I noticed today (~80F Temp) that I'm getting AFRs around 11.5 @ 4k RPMs, a brief spike at 12.0 settling down to 11.3 at redline during a 4th gear pull. Boost spikes at ~27, settles to around 24 then falls to 20 at redline.

Smooth pull through redline, no hesitation, bucking or sputtering.

Cobb AP had no significant knock readings (all less than 0.7 knock retard) through out the entire pull.

Inj. duty cycle is around 70-75%

Fuel pump relay was tested (Green relay) and was within spec (Which incidentally, Mitsu must have replaced with a green one when I took it in for the fuel line recall.)

Also noticed that there is a distinct point at which the relay switches over because you can noticeably tell by the increased black smoke out the exhaust, which is around 4k RPMs.

Evo X hivemind what say you.

 

Anyone? I received a response from Cobb, but still want to know others opinion.

 

The sensor readings can drift a bit especially when the car has just warmed up to operating temp compared to when the exhaust manifold is orange and you've been hammering on it. Usually as the sensor warms up it seems to read higher (leaner) by .2-.3 AFR from what I've seen. If that's the sensor itself or the ECU leaning things out remains to be seen but my knock never changes as the readings drift leaner. Weather can have an impact as even with all the compensations that the ECU makes for air density the 30* F cold air compared to 80* F is quite a swing for fuel requirements and load cells that you hit and easily a 5% power difference if you follow the rule of thumb.

 

Thanks!

Anymore from the hive mind?