5.9 Magnum AFR questions

[TheAussieBloke]

Hi guys,

Installed new plugs, tweaked my timing using the stock file and the cherokee premium tune and she's so much quicker now.

Question is with a data log, the 02 reading is consistent WOT at 0.780mv to 0.810mv. From what I have seen I am too rich (from what I can smell too).

Should I be leaning this out for better performance and economy.. if so where would I adjust? Being that the O2 is consistent through the rev range should i change pulse width for injectors to lean it out?

THoughts please anyone?

Thanks,
Steve

[5FDP]

You can't trust o2 sensors at full throttle, I wouldn't anyway.

On every GM I've dealt with, having a .780-.800 would be lean at full throttle and .880-.920 would be where I want it. Of course I am using a wideband while tuning wide open throttle and just looking at the o2 sensors to see what they say.

You need a wideband to know what is gong on, otherwise you are just guessing.

[Omunoz]

on the few 5.9 and 5.2 i done stock fuel at WOT is around 10 for AFR. even 4.0 are very rich at WOT

[HaasExp]

Question is with a data log, the 02 reading is consistent WOT at 0.780mv to 0.810mv. From what I have seen I am too rich (from what I can smell too).

Factory narrow bands are only useful for targeting stoichometric AFRs (lambda 1). While their output voltage can tell you whether you are rich or lean of stoich, it near impossible to quantify how rich or how lean you actually are.
The only way to tune the AFRs outside of the stoich AFR is to use a wideband O2 sensor