Looking for some pointers on maf tuning.

[TJWells]

I've gotten some excellent help tuning my vve, now i need to tune the maf I think. read through the tutorial and I gotta admit I'm lost.
My vve table is really good, I think. I have all 1's in my ben table. When I reconnect the maf and reverse what I did to log data per tutorial I see a few .9's in the upper RPM's. What should I do to tune the maf?

[joecar]

Set the dynamic air transition RPM to below idle (i.e. the RPM at which MAF+VE transitions to/from pure MAF)

[ sorry, I don't have a file in front of me at the moment to quote the table id ]

and then use wideband BEN to correct the MAF table.

[swingtan]

Joe is talking about {B8024} and {B8025}. Set them to something like 500 and 400 RPM and you should only be running in MAF measured airflow.

Simon.

[TJWells]

Thanks guys,
I assume I log ben while running on just maf then adjust maf accoringly?

[joecar]

Thanks guys,
I assume I log ben while running on just maf then adjust maf accoringly?

Yes, MAF only, running in OL (to avoid CL/LTFT/STFT trimming).

[TJWells]

Thanks joe, i would have worked in closed loop had you not mentioned that.
Cuz I miss the simple stuff all the time!

[TJWells]

What table does the ecm look at to determine what afr should be?
Lambda=AFR / Stoich where does it get what stoich should be?
Also why don't we do anything with CFCO for logging BEN? We turn off DFCO.

[joecar]

Commanded fuel is determined as follows:

PCM determines commanded EQR from:
- CL: closed loop feedback trimming to stoichiometric (EQR 1.000),
- OL: the richest EQR from the EQR tables active at that moment:
-- B3605 (OL only) (see note below),
-- B3647 (OL only) (COS) (see note below),
-- B3618 (if PE has enabled from B3608-B3616, B3619-B3626),
-- B3659 (if PP has enabled from B3652-B3658),
-- B3603 (if EP has enabled from B1601-B1603),
-- COTP (if COTP has been enabled by B0701-B0705) (I don't see a table for COTP EQR).

More info, see post #4: Summary-Notes


B3601 defines the stoich AFR to the PCM.

Actually, it's defined the other way round: AFR = stoich * Lambda
(i.e. AFR is defined in terms of Lambda, Lambda is the same for all fuels)

The wideband either has a programmable stoich AFR (e.g. LC-1/LM-1/LM-2) or assumes some value (e.g. NGK assumes 14.5);
if you use wideband Lambda then you don't have to un-factor stoich AFR out of the correction.


When DFCO kicks in it makes a rapid/step transition to DFCO fueling...

there are several reasons for disabling DFCO during tuning:
- want to avoid large fueling transitions (we're already dealing with airmass transitions),
- if DFCO AFR/EQR is not reflected in the commanded fuel pids.

You can still tune with DFCO enabled, your transient filter will now have to include a clause to filter it out.

[TJWells]

I understand why DFCO just curious why CFCO isnt an issue.

[joecar]

Since CFCO does same thing as DCFO (but in context of manual transmission clutch), it probably should also be disabled during tuning.