possible problem with PLX WB02

[jfclubby]

When logging the PLX at some parts in the log it is measuring a constant AFR when sitting on a set throttle % but in other parts of the log it will cycle up and down from 16:1 to 14:1 under a similer throttle condition. was just wondering if this is normal, and was thinking that maybe the 12V power suply to the PLX module is not constant and in turn is causing this problem, would it help to wire in a 12V to 12V dc power regulator to give a constant 12V supply to the module.

[hquick]

Hmmm...mine moves around a little but I'd only see the sorts of changes you're talking about during lean tip-in and rich decel.
You're not going into DFCO or...if running OLSD you're not hitting a semi open condition are you?

[jfclubby]

Hi Howard, this tune is in a VY series2 clubsport that is running MAFFLESS, How can i be sure that i'm not hitting DFCO or going into a semi open loop, and i'm not sure what lean tip in is. I was doing the auto VE and noticed it was not constant. Is a MAFFLESS tune always in open loop? Do i need to disable DFCO? and how do i do that?

Regards James.

[hquick]

Hi James,
can you post a current tune and log?

[charcold-bowtie]

Closed loop will have some fluctation as it is chasing the 02's so to speak.

[jfclubby]

Hi Howard, Here is the log and tune that you asked for.

[jfclubby]

Sorry Howard i forgot to upload the files, You will notice in parts of the log that the PLX goes from about 14:1 to 16:1 AFR when you have a steady throttle %. Maybe i have not set the tune up properly to do the auto VE, Note that my LTFT are disabled when doing this log.

Regards James.

[hquick]

So...is that the tune you were using with that log...because the LTFT's and STFT's are enabled in that tune?
Or...are you saying that's your latest tune and the LTFT's were enabled after running that log?
Log looks pretty good to me. Looks like the O2's are trimming your fueling and you are definately going into DFCO.

See in the attached pic where your AFR goes to 19.6 and your timing goes to -2.5?
That's DFCO (decel fuel cut off). The second pic shows the 'sawtooth' look of your O2's switchingbetween rich and lean to try and hit 14.63 (14.7) you have in your commanded fueling table (B3647). Basically...everywhere you see 14.63 in that table is where your O2's are adjusting your fuelling.
There are alot smarter guys here than me so hopefully they will chime in but the log looks ok to me.

[hquick]

Oh...and you need to disable the LTFT's and STFT's for autoVE.

[JezzaB]

Looking at your tune. Its because you are in closed loop. To put the tune into open loop so you can do an AutoVE set:

B3801 to DISABLED
B3802 to 140oC
B4205 to 140oC across the board
B3647 everywhere it says 14.63 set to 14.5
B3636 to 140oC
B3313 to 140oC
A0014 1.00 across the board

That should do the trick

Then look up what all of these things do.

BTW You might want to richen up the PE or Commanded AFRs up top a bit. With those that lean and the VE table low it could be very lean
Jez