lean spike on take off, help
Thread Starter
TECH Resident
Joined: Jul 2010
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From: VA
lean spike on take off, help ive got my tune closer and im starting to notice when ever i hit the pedal from 0% tps to anything under 2-2.5k rpms it spikes lean off the A/F gauge 18+ for about a sec then goes back to normal 14-15 cruising levels and car runs fine, the car stumbles when it goes lean then picks back up again also, when i was logging i noticed both o2 inj banks (i think it was) drop way down to the hundreds under this lean condition, then go back up to the 500-700 hundreds or what ever they normally bounce around in
could this be an injector tune problem, as when i put in my 60# inj (running at about 72# at 60-64psi fp) i wanna say this started doing this as i had no throttle repsonse or lean condtions on stock injectors and the tune is basically the same one
could this be an injector tune problem, as when i put in my 60# inj (running at about 72# at 60-64psi fp) i wanna say this started doing this as i had no throttle repsonse or lean condtions on stock injectors and the tune is basically the same one
I would begin by looking at how well "MAF airflow"
and "Dynamic Airflow" track each other during these
tip-in events.
When you roll it on, the PCM ignores the MAF for
some interval until MAP becomes "steady" again.
If the MAF airflow is much higher than the Dynamic
(speed density - MAF blend) airflow, you will have
an abrupt change in the air mass used in the moment,
vs what you would see in a steady-state-tuned,
steady-state-running scan.
Now, when you do airflow tuning, you are going to
embed any residual fuel-side errors into the VE & MAF
by your process. Big injectors often have different
and significant offsets which become a part of
narrow-pulse-width fueling accuracy, hence tuned
airflow accuracy if the injectors are not well modeled.
If you found it necessary to mess with the VE table
low end, after the injectors went in and after using
proper IFR table values, this would indicate that the
offset is significant, and dealt with wrong. Give that
a look & some recollection.
and "Dynamic Airflow" track each other during these
tip-in events.
When you roll it on, the PCM ignores the MAF for
some interval until MAP becomes "steady" again.
If the MAF airflow is much higher than the Dynamic
(speed density - MAF blend) airflow, you will have
an abrupt change in the air mass used in the moment,
vs what you would see in a steady-state-tuned,
steady-state-running scan.
Now, when you do airflow tuning, you are going to
embed any residual fuel-side errors into the VE & MAF
by your process. Big injectors often have different
and significant offsets which become a part of
narrow-pulse-width fueling accuracy, hence tuned
airflow accuracy if the injectors are not well modeled.
If you found it necessary to mess with the VE table
low end, after the injectors went in and after using
proper IFR table values, this would indicate that the
offset is significant, and dealt with wrong. Give that
a look & some recollection.
Thread Starter
TECH Resident
Joined: Jul 2010
Posts: 905
Likes: 0
From: VA
sorry guess i should of had some more info, im tuning in 2 bar SD tunig no MAF, i have my STFT dialed in and LTFT disabled, they are dialed in to around 6-7 +/- in STFT, car runs great just like it did before injector swap and all so im feeling i missed something with tuning the injectors but in saying that im not trying to steer anyone away with something else i might of over looked
when i tuned for my injectors i looked at how others had there 60# injectors tuned and out of the 3 tunes the only thing i saw changed really was the flow rate so that was the only thing i changed, as soon as ur in throttle and stay in it, wether ur WOT or just normal acc or a mix of ether u get zero hesitation and no craziness in the A/F guage
all my tunes/logs are on my laptop so when i get home and get internet i can load them up here for you
when i tuned for my injectors i looked at how others had there 60# injectors tuned and out of the 3 tunes the only thing i saw changed really was the flow rate so that was the only thing i changed, as soon as ur in throttle and stay in it, wether ur WOT or just normal acc or a mix of ether u get zero hesitation and no craziness in the A/F guage
all my tunes/logs are on my laptop so when i get home and get internet i can load them up here for you
Thread Starter
TECH Resident
Joined: Jul 2010
Posts: 905
Likes: 0
From: VA
i tryed messing with fuel transeit since some say that can cause it, i also played with injector timing and pulse width, none fixed my problem and if anything made the rest of my tune worse, probably would have to tune for it but
heres the best tune all around on my car, car runs and pulls awesome minus the listed problem
and the log data is just me in the drive way idling and playin with gas, it does the same lean bs when driving so its easier to just do in idle, u can watch the tps % and watch my o2 sensors just drop way down and lean out to the double digits then back up
any suggestions or anything id appritiate
heres the best tune all around on my car, car runs and pulls awesome minus the listed problem
and the log data is just me in the drive way idling and playin with gas, it does the same lean bs when driving so its easier to just do in idle, u can watch the tps % and watch my o2 sensors just drop way down and lean out to the double digits then back up
any suggestions or anything id appritiate
