STFT (O2 feedback)

[kev]

3in Maf-T with PTE 680 injectors on a 99 GSX

Setup my Maf-T for my larger injectors. At idle, My LC2 wideband shows around 13.5 to 14.7 afr and my short term fuel trims show -25. O2 voltage shows .9. Dead O2 sensor or maybe vacuum leak? I don't know much about logging. What should I check?

I also go really lean when revving at idle and the car stumbles. Maybe the two things are related.

 

[AWD-Tony]

Post a log of it idling. Did you check for boost leak/exhaust leak? You have wideband in the rear and front O2 is stock or Wb in front?

In closed loop, O2 should be cycling.

 

[kev]

Post a log of it idling. Did you check for boost leak/exhaust leak? You have wideband in the rear and front O2 is stock or Wb in front?

Here is the evoscan latest log. I just noticed my ISCsteps are quite high. 80 at idle is kinda excessive?

Front O2 is in stock location, LC2 wideband is on the downpipe. No exhaust leaks. Rear O2 is inoperable

 

[AWD-Tony]

Oh, thought you had link. I can't open that file. ISC should be around 30 at idle fully warmed up.

Fill out your profile page when you get a chance

 

[kev]

I took a screenshot of my log for you. I am going to fill out my profile right now

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[kev]

I added to "DSM profiles" so I don't think I did that right

 

[AWD-Tony]

Great!!

Sorry I have 0 experience w evoscan. You also want to move this thread to tuning or maintenance section.

Go to forum
Tuning and engine management
Post new thread

Go through the newbie section on the website.

Also want to read this

http://www.dsmtuners.com/threads/wa...r-receive-no-replies-from-the-wisemen.443297/

You prob have to dial in the injectors first.

 

[doubleclutch]

sounds like it isnt going into closed loop because you are running to rich. I don't know evoscan, but if you are pulling -25 (% i'm guessing?) out you are not actually sucking in as much air as you are telling the car. It probably doesn't cycle because it isn't in closed loop and it is pig rich.

 

[AWD-Tony]

Is that screenshot when the car was fully warmed up? Coolant temp is 129

 

[kev]

I tried setting my injectors through ECUflash, but for some reason it doesn't hold. Maybe there is a setting that keeps the program from overwriting the ecu during the reflash process? So I have used the base and aux control on the Maf-t to compensate for my injectors. That's how I did it before replacing this motor without issues.

Anyways, No the car was not fully warmed up. Maybe that is part of the issue, but during warm up there should not be a -25% correction right? And why is my ISC steps at ~80? Seems excessive. Maybe that is why the car goes temporarily lean when revving and stumbles? If I ease into the gas I don't have that issue.

 

[AWD-Tony]

It should run rich at cold start, I believe until the O2 warms up, I could be wrong (But not -25%). Then it should oscilate from .9 - .05 volts (closed loop).

Search 2g biss adjustment. That will adjust the isc correctly. But before you do that, you have to check other things. YouTube jafro tuning 101. Think there’s two or three videos. He does use ecmlink though.

 

[kev]

I know how to adjust it, I will do that tonight when I am off work thanks..

Will that cause me to suddenly go lean when pressing the gas during idle?

 

[AWD-Tony]

You can burn the isc motor when you adjust it if stuff is out of wack. Check those videos first before adjusting the biss. Honestly don’t know if that’s causing your lean condition. Fix the idle issue first and see from there.

When you pump the gas and let go, it will go lean for a second or two but should return to around 14.7 within a few seconds.

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[kev]

It goes lean when I first give it gas.

I will check out that video later tonight. Thanks for your help. I will post back results.

 

[AWD-Tony]

Sure thing! You may have better luck by posting on the engine management tuning section. I’m sure there are members with evoscan that can be of better help.

 

[kev]

Everything is good. Took the car out for a break in last night. STFT still shows -25, but LTFT shows 1%. So I should follow the LTFT in this case?

The injectors weren't dialed in properly. I thought I had the 2.0 Maf-T so I followed those directions. I guess I actually have the older version Maf-T. Some of the knobs are backwards.

And the idling problem was the ISC. I need to adjust it, but unplugging it has fixed the issue temporarily.

 

[AWD-Tony]

This is from emclinks wiki page

http://ecmlink.com/wiki/maftcalibrationbywbo2

Rev Tuning (STFT) 150hz

1. After you are done with idle tuning, rev the engine and keep it at the 150 Hz level.
2. Watch your STFT's for needed adjustments.
   • If STFT fuel trims are positive, add air at the 150 Hz point in the airflow table.
   • If STFT fuel trims are negative, subtract air at the 150 Hz point in the airflow table.
   • Adjust the airflow 1% for each 1% fuel trims are adjusting fuel.

 

[doubleclutch]

STFT is used to adjust LTFT once the right variables are seen by the vehicle. You need to get STFT and LTFT close to zero if possible.