sooo lean....why?? Options

[NOMIEZVR4]

i have a logger and my car has always run realll lean and i still havent figured out why. i have a 90 laser with mods in sig, my cat is on right now and my dump is not on the car. my maf is not hacked at all. my fp is not rewired or anything. i need some suggestions as to why my car is running lean. im running 12-13lbs of boost. my logger displays the following:

fuel trim lo 118%
mid 94%
hi 116%
02 volt at WOT .92-.94
timing at WOT 11 degrees(why so low??)
knock maximum 30+ (in 2nd gear around 5k rpms)

if there is anymore info that you need, please ask, i need suggestions, also i run 93 octane.

[natedogg]

so the car only uses the trims when its not at wot??

Exactly. The fuel trims come from the ECU monitoring the O2 voltage in closed-loop mode. The O2 trim changes constantly with the cycling O2 voltage. Overtime this changes the long term fuel trims. The low trim is for idle and parking lot speeds. The mid trim is for cruising speeds. The high trim is for acceleration but not at WOT. Its called closed-loop mode because the ECU is monitoring feedback from the O2 sensor to tell it how rich or lean the car is actually running. It then adjusts the short-term O2 trim and long-term fuel trims to approach more fuel efficient injector command tables and continues this process as long as the car is running. Trims are there basically to keep the car running at maximum closed-loop power/responsiveness/efficiency in changing weather conditions and driving styles.

Now, open-loop is the mode that the ECU changes to for WOT. It has a set fuel control algorithm based on the airflow signal and possibly the coolant temperature signal. The O2 sensor voltage is ignored which makes sense because it doesn't cycle anymore but stays at a constant voltage near 1 volt. Obviously, it is called open-loop because all feed-back from the O2 sensor is ignored.

There is more info on this stuff at www.tmo.com

what should i tune my car by?

Tune by knock. The knock sensor is the true tell all for how well your car is running. If you are seeing lots of knock you are more than likely running lean at WOT. If you have the new version of the pocketlogger software you can also tune by injector duty cycle. Generally, you want to try to keep the duty cycle at or below 90% at WOT, but if you still see knock at this duty cycle don't be afraid to turn up the fuel some more. You may be able to squeeze a little more fuel out of your injectors yet.