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driver456
May 8th, 2006, 09:00 AM
When in open loop you have "Commanded fuel in OL"When exactly is the PCM using the VE table for fueling,when it goes into closed loop? How does that work?.......................Paul
TAQuickness
May 8th, 2006, 09:19 AM
Closed loop occurs after ETC > ?*F (after the car warms up), and under non WOT conditions. I can't remember, but I think it's in open loop under DFCO conditions as well.

If you are running the MAF, the PCM uses an interpolation of MAF and VE under 4k RPM. Over 4k is all MAF.

been a while since i've run in closed loop.
driver456
May 8th, 2006, 09:26 AM
Closed loop occurs after ETC > ?*F (after the car warms up), and under non WOT conditions. I can't remember, but I think it's in open loop under DFCO conditions as well.

If you are running the MAF, the PCM uses an interpolation of MAF and VE under 4k RPM. Over 4k is all MAF.

been a while since i've run in closed loop.
OK,Thanks,Yes I still have the MAF.If I stay in OL with MAF,It still uses the MAF after 4K rpm?
TAQuickness
May 8th, 2006, 09:42 AM
yes. OL and CL are entirely different than SD or MAF opperation.
SSpdDmon
May 8th, 2006, 10:05 AM
Yeah, don't confuse OL or CL with SD. Think of the VE table as the base or foundation if you will. The numbers in that table tell the PCM, "this is the value you need to enter into your fueling equation to achieve a stoich (14.63) AFR."

The commanded fueling in OL uses the VE table just the same as in closed loop. The only difference is in OL there's no corrective feedback from the O2 sensors (fuel trims). The OL table is basically an adder/subtracter table. Since the PCM knows through the VE table where stoich is, it can compute where any other AFR is....BUT...this is assuming the VE is correct. It's kinda like the PE table, only the OL table looks at MAP and RPM instead of just RPM.

If the MAF is disabled, you are in SD mode and the PCM relies solely on the VE table. If the MAF is enabled, than it's both the VE and MAF that are used for fueling.

In the end, you have a commanded AFR. CL is just the PCM's way of making sure the actual AFR matches the commanded.