Quick question about Long Term Fuel trims

[WeathermanShawn]

I can not find B3647..

Is this a COS?

IMO, when MAF is enabled B3618 dictates Commanded Fueling. Your OS, may be different, but personally I would modify your B3618 as your Commanded Fuel.

[BRD-PREY]

This is my table.

[BRD-PREY]

Yes I have COS5 my bad. I should have said something. I'm pretty sure I've got it correct, but you never know.
Ed
Joecar help! Does b3647 function in MAF only. Should I leave PE at 1.0?

[joecar]

I have B3647set to what I want for enrichment, B3618: PE Modifier Based on Rpm (EQ): is set to 1.0 . With B0120 set to 600 rpm it will still use table b3647 right?

Yes, in OL it will use B3647.

Remember: MAF and OL/CL are independent of each other.

So with B0120 set to 600, PCM does this:
- above 600 rpm PCM reads MAF (and ignores VE) and computes cylinder airmass,
- PCM determines whether it should be in CL mode or OL/PE mode,
- for OL/PE mode, PCM sees B3647 is richer than B3618, so it uses B3647 to command fuel.

[joecar]

yes, I'm asking if commanded EQ is 1.13 in B3647 for 4400rpm at 80- kPa. Then when my engine is at 4400 rpm 80- kPa even in MAF only mode I still have 1.13 commanded right. Right now all of my PE are set to 1.0. So all of my commanded fueling is a reflection of B3647 if my coolant temp is in range. What I was asking is with VE off by setting b0120 to 600 rpm I'm still driving commanded fuel by B3647 right.
In summary should I ever have anything other than 1.0 in my PE tables?

Some people set their PE table to look like the last two columns of B3647.

[joecar]

I can not find B3647..

Is this a COS?

IMO, when MAF is enabled B3618 dictates Commanded Fueling. Your OS, may be different, but personally I would modify your B3618 as your Commanded Fuel.

Yes, B3647 is the COS version of B3605.

B3647 is looked up using RPM vs MAP, gives more control over commanded fuel, but requires ECT multiplier table.
B3605 is looked up using ECT vs MAP.

[joecar]

Yes I have COS5 my bad. I should have said something. I'm pretty sure I've got it correct, but you never know.
Ed
Joecar help! Does b3647 function in MAF only. Should I leave PE at 1.0?

B3647 functions in VE and MAF modes.

The richer of B3647 or B3618 is used to command fueling...

altho Shawn did make some curious observations with B3618 set to 1.00 while running from the MAF.

Also, be aware that any cell in B3647 that is 1.00 will cause STFT trimming while in OL, this causes wideband BEN to be 1.00... you want to avoid this by avoiding 1.00 (use 0.99 or 1.01) in B3647.

[joecar]

Your MAF table is wrong, Shawn said above that the "slope" of it must be maintained (the "slope" is a 3rd order polynomial curve... look at the GM stock MAF table, your new MAF table must have a similar constantly increasing slope/curve looking like the GM table, except the whole curve shifted up/down/left/right).

[joecar]

...
altho Shawn did make some curious observations with B3618 set to 1.00 while running from the MAF.
...

You can test this out... (post some log/tune files)...

set B3618 to 1.00 and do a logging session; then in this log look at GM.EQIVRATIO when PE conditions are met (as in B3616), see which of B3618 or B3647 it follows (using the scantool->tunetool dynamic cursor linking feature)... when PE conditions are met, if EQIVRATIO is 1.00 then it follows B3618 (this is bad, not enough fuel), otherwise it will follow B3647;

Shawn says that EQIVRATIO will stay at 1.00... but do the experiment since there are conditions to this that we are not aware of, such as FUELSYS may not necessarily say OL, but OL-drive... or even CL in which case B3618 is commanding fuel (so it should be set sufficiently rich, i.e. same value as last 2 columns of B3647).

[joecar]

B3647 is the COS open loop commanded fuel table, it functions during OL in both VE and MAF modes.

B3605 functions the same.