LTFC Cell Values

[Blacky]

If you're not using a wide band O2 sensor to tune the VE table then...

You need to be in closed loop so that the PCM learns the LTFTs.
Once you have collected a lot of LTFT data you need to create a pivot table in Excel (note EFILive V7 does this automatically).
The pivot table should plot LTFT against whatever axis your VE table is indexed by. For example, in the VT 5.7 commodore the VE table is index with RPM and MAP (see attached image).

To create the pivot table, you need to reduce the RPM and MAP values into ranges that match your VE table indexes, i.e. 400,800,1200,1600 RPM etc and 5, 10, 15, 20, 25 MAP etc.

See image where only the RPM, MAP and LTFT colums are left (I deleted all the others). The two extra columns of RPM and MAP labels were created using the formulas:
=+TRUNC(A2/400)*400 (for RPM, 400 defines the step size)
=+TRUNC(B2/5)*5 (for MAP, 5 defines the step size)

The create a pivot table (see image) which shows the +/- percentages you should add to the VE table to bring your fuel trimes closer to zero.

Note, you can't use this method to tune power enrichment (PE) mode because the PCM does not use/updatre LTFT in PE mode. For that you need a wide band O2 sensor.

Regards
Paul

[Blacky]

I don't believe it stayed in Open Loop all the time.

It did stay in open loop, the column headed FUEL1 shows the Open Loop flag: bit 2 = "1" when in closed loop.

Unfortunately Excel is brain dead when it comes to bitwise logic. To see the breakdown of the FUEL1 column, you have to use the following formulas:

O2 Sensor Ready =+IF(MOD($L2,2)>0,1,0)
Closed Loop =+IF(MOD($L2,4)>1,1,0)
Learning =+IF(MOD($L2,8)>3,1,0)

See image.

Regards
Paul

[Chuff]

Thanks Paul,

My bad. I said I logged via Open Loop when in actual fact it was closed loop.

What you posted in the previous post I already understand. What I would like to know is what data is valid as being in a closed loop, so I can make sure I only use that data and no other. That's why I uploaded a copy of my log file.

From what I can gather I should be using data based on the FUEL1 value, but I am getting 5 different values. This is a summary of the FUEL1 data:

FUEL1 CountOfFUEL1
17 8
21 2
81 2412
83 9
85 1808

As you can see, most are either 81 or 85. Which represents Open Loop data, or is it another field/value altogether?

Thanks for all your help.

[Blacky]

I realised I did not answer you question, see my post before yours.
Paul

[Chuff]

Got it. Too quick for each other.

Thanks.

[Blacky]

Just for clarity, to break down ANY bit field use the following formulas:

 
BIT 0 =+IF(MOD($L2,2)>0,1,0)
BIT 1 =+IF(MOD($L2,4)>1,1,0)
BIT 2 =+IF(MOD($L2,8)>3,1,0)
BIT 3 =+IF(MOD($L2,16)>7,1,0)
BIT 4 =+IF(MOD($L2,32)>15,1,0)
BIT 5 =+IF(MOD($L2,64)>31,1,0)
BIT 6 =+IF(MOD($L2,128)>63,1,0)
BIT 7 =+IF(MOD($L2,256)>127,1,0)

That will result a "1" when the bit in the bit-field is "1" and a "0" when the bit in the bit-field is "0".

The BIT numbers come from the EFILive V4 flag definitions - see image.

Regards
Paul

[Chuff]

Just for clarity, to break down ANY bit field use the following formulas:

 
BIT 0 =+IF(MOD($L2,2)>0,1,0)
BIT 1 =+IF(MOD($L2,4)>1,1,0)
BIT 2 =+IF(MOD($L2,8)>3,1,0)
BIT 3 =+IF(MOD($L2,16)>7,1,0)
BIT 4 =+IF(MOD($L2,32)>15,1,0)
BIT 5 =+IF(MOD($L2,64)>31,1,0)
BIT 6 =+IF(MOD($L2,128)>63,1,0)
BIT 7 =+IF(MOD($L2,256)>127,1,0)

That will result a "1" when the bit in the bit-field is "1" and a "0" when the bit in the bit-field is "0".

The BIT numbers come from the EFILive V4 flag definitions - see image.

Regards
Paul

JACKPOT!

That's everything I need to know in order to proceed.

Woo-hoo!

Thanks.

[Chuff]

Doh!

1 more question.

Assuming Fueling Mode is in 'Closed Loop', should I exclude data where Fuel Learning status is not Learning, or is this valid data aswell?

Thanks.

[Blacky]

Almost all data is valid, even when the PCM is not learning it is still using the most recent LTFT values. And those values are what you want to apply to your VE table.

The issue with dropping data is to remove all data frames where the PCM is modifying the fuel ratio that is calculated from the VE using factors other than *just* the VE table. For example, during deceleration fuel cutoff and during large throttle changes.

Actually, now that I think about it for a bit, it is probably best *not* to override the open/closed loop of the PCM. When the PCM goes into open loop, you should probably discard all those frames. Open loop will be (should be) active during wide open throttle and decel fuel cut and other non-LTFT controlled fueling situations.

Regards
Paul

[Chuff]

Hi Paul,

Just so I understand are you saying that I should not use your Closed Loop macro and just log data as per normal. Once I have gathered the data I should only use frames that are marked as Closed Loop?

What about Learning mode? Should I only use frames where the value is TRUE or should I not filter on this value at all?

Right now I'm writing some Excel VBA code to delete all unnecessary columns & rows, as well as add additional columns representing the FUEL1 bit values, as well as the MAP & RPM Labels as you have already detailed. Once I have this, I intend transposing the data into a pivot table and update the VE Tables with the results. Until I know what has to be excluded I can't complete the spreadsheet.

So which values should I filter on?

Sorry for all the questions, but if I start making assumptions, and get it wrong, things may go bad.

Thanks.