Maf and closed loop?

[FreshDA9]

I am confused with the tutorials I have read. They have you tune the VE in open loop then the maf in open loop. Could i just tune the Maf in closed loop? when WOT doesnt the PCM switch from CL to OL; if so where could i find this value. I simply would just log my AF on my maf table under WOT and adjust accordingly correct.

[joecar]

Yes, you can run the MAF in CL.

Which tutorial...?

[joecar]

PCM stays in CL when going WOT... (atho it applies the last valid positive trim, not the current trim).

[FreshDA9]

the AutoVE tutorial mentions about tuning the maf in OL. Then i was also reading the Calc MAF airflow from VE table. so the ecm doesn't have a transfer when it meets certain conditions that would switch it from CL to OL at WOT. I guess i will have to re-read these again.

[darcy]

I thik you're confusing modes. It's not OL at WOT, its PE.
Power Enrichment isn't Open Loop, although it's not commanding stoich, Learned Fuel Trims (positive only) are applied in PE.

[FreshDA9]

So PE will only add positive fuel trims to achieve its target. I have my PE set to 12.8 and during a run it was a flat 12.3 so in this case it would not lean out since it would be a negative value to reach 12.8....

But if I tune the VE and MAF in OL then PE would not be effected until i put the truck back into CL?

[darcy]

So PE will only add positive fuel trims to achieve its target. I have my PE set to 12.8 and during a run it was a flat 12.3 so in this case it would not lean out since it would be a negative value to reach 12.8....


No, the PCM has no way of measuring AFR outside of stoich. Trims are only learned during closed loop and the last valid trim is applied during PE mode.
This applied trim may be 0 or +ve.

Correct, there are no fuel trims applied in Open Loop.

[FreshDA9]

Hmm looks as if i need to read more about GM and how they function their PE or just say F the maf and stay OL and maybe do a custom OS later when i decide to go boost.

[joecar]

So PE will only add positive fuel trims to achieve its target.
...No, not to achieve it's target (the PE table is the target), but to provide a safety net.

[joecar]

See post #4 here for a summary of modes: Summary-Notes (http://forum.efilive.com/showthread.php?14188-Summary-Notes)

[joecar]

the AutoVE tutorial mentions about tuning the maf in OL. Then i was also reading the Calc MAF airflow from VE table. so the ecm doesn't have a transfer when it meets certain conditions that would switch it from CL to OL at WOT. I guess i will have to re-read these again.Calc.MAFT corrects the VE table using CL/stoich LTFT's and non-stoich wideband correction...

the first iteration will probably have non-zero WOT trims, but with the second iteration the trims will have narrowed down close to zero

( I sometimes manually subtract out any WOT trim if it's present after I paste the SELBEN map to the VE table )

Calc.MAFT and Calc.VET rely on the trims being cleared when you flash (this is the case with LS1A/LS1B).

[FreshDA9]

Im still reading the summery notes you linked me to and trying to understand it all. I should have ore time to read over it tomorrow and do some testing on my tuck after words. Im understanding about 50% of it but im more of a hands on person then a reader (always had a hard time in school with understanding the text in front of me). Thank you guys.