I have a question. Under normal driving conditions the ECU is in closed loop mode where it monitors O2 content and makes adjustments to short term and long term fuel trim for each bank for optimum catalyst efficiency.

When you are driving Wide Open or on a dyno you are in open loop mode, or speed-density mode. It basically stops monitoring O2 and instead uses a fixed map based on airflow (through the MAF) ECT and RPM.

does anyone know if the trim values are applied to during open loop operation?


What I am really asking is: We know that the ECU learns at part throttle and will compensate for atmospheric changes and add-on parts at cruising speed, but does it compensate for anything wide open?

Do you really see changes on a dyno WOT after some miles for the ecu to adjust to new headers or intake.

Give me your thoughts.

 

The short and long term learns are much faster than most think. Long term is relative and can be fully reset in less than 3 minutes short term in 5 seconds.

Now emission test ready memory FLAG may require 30 miles and multiple cranks but that has nothing to do with WOT.


Nissan has always relied heavily on MAF [grams per second] to calculate WOT even prior to 1996 when base WOT parameters were burned into chip.......the MAF could still add/subtract up to 22% fuel from preprogrammed amount.

Is the dyno operator telling you it will get better after you drive awhile?

 

No, I am just curious if it will get better after a while. I know that up until very recently at least the Lexus/Toyota V8's had a fixed open loop map that was only based on airflow, throttle position, and coolant temperature - it would also monitor for knock on each bank, but that didn't make corrections to the map it just did an emergency timing retard. If you added headers or did head work - it would run better (it would see increased airflow and compensate), but it was never optimum - which led to the use of a unichip type piggyback controller which would give big gains.

It would optimize the closed loop mode for normal driving - just not WOT. I was just wondering if the G35's are the same.

 

q45tech, will the ecu go into a different a/f map to compensate a wot run? iow, dump more fuel to compesate? thanks.