Baseline datalog on 09 Cobalt SS/TC - questions on fuel trims

[metroplex]

I am gathering data for a baseline on my 2009 Cobalt SS/TC (LNF 2.0L) in preparation for a K&N short ram intake install. I've heard that it may skew the LTFT unless the filter is rotated so the metal rib is at the 11 o'clock position. However, I used my ELM327 datalogger (v1.5 BAFX) and the Torque Pro app to monitor LTFT, STFT, etc...

What I found was the LTFT remained at 0% regardless of load/RPM, while the STFT fluctuated between -5.47% and +11.72% essentially inline with the AFR on my RPD (the OEM display on the A-pillar that can show AFR based on the wideband O2) depending on what I was doing. While idling, the STFT hovers very closely around 0% (14.7:1).

Is this normal behavior?

If so, I at least have a baseline to see if the K&N SRI will throw off the LTFT and STFT. I am interested in the HPTuners VCM Suite so I can custom tune my LNF, but I've been using SCT's Pro Racer Package and Advantage software for about 10 years on my Fords and am unfamiliar with HPT.

[Iam Broke]

Sounds like your STFT's are close to normal. The LNF seems to like to settle in at +0.8 to +1.6 LTFT when the STFT's are spot on. Close enough for most.

If you log STFT + LTFT vs MAF freq you can get a better idea of the average in most cells and adjust the MAF freq accordingly. Need to drive smoothly through the accel & decel for a long trip.

Some unplug the purge solenoid to force the LTFT's to 0 then log just the STFT's. I always left it connected and used the sum of the two in a custom pid.

[metroplex]

I don't have the HPTuner/VCM, and have been using the ELM327 and Torque Pro android app. I can't seem to find the PIDs for MAF Frequency. I will test out the purge solenoid today to see what's up, I know for a fact it is still connected. Do these frequently fail?

[Iam Broke]

No, the disconnect will pop a CEL if you can't tune it out but they don't fail often. I meant unplugging it so the ECU thinks it's failed. That will force the LTFT's to zero for tuning.

[metroplex]

Oh no, I never touched the harness or vacuum tube. I will check to see if the valve is physically bad though later today. Do I need to blow air through the valve with my mouth, or can I use a vacuum pump on the nipple instead?

According to Rock Auto, the purge solenoid is a hot seller for the LNF, another YouTube video showed a guy blowing through his solenoid and said it only lasted 1 year.

The Torque Pro app for Android does have MAF flow rate, which I believe is a standard/universal OBD2 PID (in gram/second). Would this be of any use?

[Iam Broke]

Only if you can plot it vs STFT's. For tuning, a specific g/sec relates to a specific MAF freq. We alter the tables to bring them in line.

I believe the purge sol should pass air when energized only.

[1nastycobalt]

^^^ I second that.