AFR not changing under WOT below 3k rpm

[ever_green]

i have been monitoring the Air to Fuel ratio for my impreza using scangauge 2. im using one of the official xgauge codes from scangauge's own website. The numbers reported seem ok if not too static. But AFR does not change under WOT below 3k rpm. example in 4th gear at about 2000rpm & 30mph under WOT the AFR stays in the 14.5s! (car doesn't go into open loop, it only enters open loop when engine is cold or if i climb over 4k rpm). if i flatout keep WOT and let the RPMs climb past 3k then AFR dips to 13s and eventually as low as 11 by redline. but not so under wot below 3k rpm. is this my car or is there something wrong with scangauge?

[RobertISaar]

could be the car....

a lot of manufacturers impliment delays when it going into power enrichment mode, some are time based, others RPM, other airflow, others based on how quickly the throttle is opening, others are a combination of all of them.

try coasting at 3500RPM in some gear, then lean into it and see if the AFR changes almost instantly compared to starting at a lower RPM.

[ever_green]

tried that and the afr stayed between 14.2-14.5. did not venture past 4000rpm because that takes me over 75mph in that gear. but accelerations off the line can take it as low as 11.5 if i go WOT in 1-2 gears.

[Daox]

I'd say its your engine. Most cars stay in closed loop unless you get into a moderately high rpm range, even at WOT.

[serialk11r]

Yea even my 2000 MY car with cable throttle 1ZZ and narrowband sensors doesn't go open loop until who knows how many rpm. It said closed loop at well over 3000rpm and heavy throttle.

On newer cars with wideband sensors I think it might be more common to run rich to extend catalyst life, but not sure. Wideband sensors allow closed loop enrichment.

I'm not sure what ideal load is if 100% load is stoichiometric, but I'm guessing probably 80-90 :O I know peak BSFC of this engine is pretty ****ty at full load (I think in the 260s g/kwh) according to the Toyota development paper, which is what leads me to think that.

[ever_green]

Originally Posted by serialk11r

Yea even my 2000 MY car with cable throttle 1ZZ and narrowband sensors doesn't go open loop until who knows how many rpm. It said closed loop at well over 3000rpm and heavy throttle.

On newer cars with wideband sensors I think it might be more common to run rich to extend catalyst life, but not sure. Wideband sensors allow closed loop enrichment.

I'm not sure what ideal load is if 100% load is stoichiometric, but I'm guessing probably 80-90 :O I know peak BSFC of this engine is pretty ****ty at full load (I think in the 260s g/kwh) according to the Toyota development paper, which is what leads me to think that.

actually 260g/kw/h or 0.4 lbs/hp/h is pretty good. typical petrol engines have 0.5 sfc. i haven't seen much cars with better than 0.4lbs/hp/h except the new turbo diesels.