Mustang/F150 Open/Closed Loop Fueling for 5.0s

[Roland@pcmtec]

Question: How is open loop (eg WOT) fueling calculated for Gen 2/3 5.0s.

Note: Open loop values are used as as feed forward to the closed loop fuel value (eg where STFT is applied using the wideband to achieve the requested target. So you can ignore the fact everything says "open loop" when in fact it will be operating in closed loop except for various conditions such as being too cold for the wideband to function.

Note: The answer is similar for ecoboost vehicles, however with many extra protections put into place that are not taken into account into this guide.

Note: This is a work in progress and has been deciphered from reading assembly code, this guide should be taken with a grain of salt and everything tested on a dyno to ensure it works as described.

 

Short Answer for 15-17 (Gen 2)

auF31663 The WOT open loop fuel table to temperature compensation to avoid cold misfire - This determines the open loop feed forward commanded lambda value when the engine is warm and there are no other limits or features preventing it from running in normal conditions

auF29139 Base Open Loop desired exhaust lambse fuel table - This is used when cold. Ensure this is calibrated at high loads.

Long Answer for 15-17:

Note this is a simplified answer without the flex logic or OPSS logic switch (disabled in all Mustang cals I've looked at) taken into account.

auF0156 Open Loop Delay - The time delay specified this table (set to 0 in most vehicles) is first waited to expire. before this expires

Before this timer expires the vehicle is in "minimum enrichment mode" which can be determined via datalogging "MID71841" Power Demand Min Enrichment flag; while waiting for the delay to expire. It will be set to 1 if in this mode.

When in "minimum enrichment mode" the commanded lambda will be determined by the following calculation

auF31663 The WOT open loop fuel table to temperature compensation to avoid cold misfire

auF31661 The WOT open loop fuel table. This is not used in the 15-17 unless the "minimum enrichment delay is set above 0. If it is the calculation is as follows.

MID55410 = Desired LAMBSE for performance (Power Demand - LBT)

LAMBDA (MID55410) = MAX(auF31663, auF31661) Eg it takes the maximum of the misfire limit and the WOT open loop fuel table. Ensure that you configure both tables at WOT to be the same to ensure when cold the engine does not run lean at WOT. Note: Typically in a 15-17 auF31661 will not be used and this will not be an issue.

auF31664 is the FFV OEM Ford flex fuel equivalent of this table.

When the engine is "cold" it will use the following table auF29139 Base Open Loop desired exhaust lambse fuel table

The engine is considered cold before ECT has reached the temperature upon which auF29139 == 1.0 at the lowest load. Eg 50°F according to this calibration FR3A-14C204-CNF as this is when the wideband is considered usable for closed loop operation.

Eg when MID63525 "Engine is too cold to run closed loop stoich." is set to 1.

 

Short  Answer for 18+ (Gen3+)

auF63644 Desired Lambse during power demand (lookup based on ECT,RPM)- This determines the open loop feed forward commanded lambda value when the engine is warm and there are no other limits or features preventing it from running in normal conditions. IMPORTANT NOTE for up to 4 seconds the value will be used from auF37057. Recommend calibrating auf37080 to 0 like the 15-17 for big PD blower cars which make big boost down low. Especially as this only kicks in at gears 7+ you might notice it unless you are on the autobahn.

auF63635 Base Open Loop desired exhaust lambse fuel table - This is used when cold, ensure this is calibrated for high loads.

Long Answer for 18+:

Min enrichment delay phase:

Where the 18+ differs from the 15-17 is it does indeed utilise the "MID71841" Power Demand Min Enrichment flag

By default this is 4 seconds at low rpm. This could cause trouble on PD blower cars.

By default for these 4 seconds it will use the following table. This may catch you out, be sure to calibrate it or remove the delay timer.

auF37057  Desired Lambse during power demand (lookup based on Engine Speed, MID113340),while waiting for delaytmr(auF0156) to expire

Like the 15-17 when in "MID71841 Power Demand Min Enrichment" for this 4 second window the lambda is calculated as follows:

LAMBDA (MID55410) = MAX(auF63644, auF37057)

Ensure that you configure both tables (auF6344, auF37057_ at WOT to be the same to ensure when cold the engine does not run lean at WOT when in this 4 second window OR set the delay phase (auF37080) to be zero like the 15-17.

Normal open loop control outside of min enrichment delay phase

When outside of this min enrichment delay the following table is used. This the most important table to calibrate.

auF63644

auF63645 is the FFV equivalent if you use the built in OEM flex system.

When the engine is "cold" it will use the following table auF63635 "The base open loop fuel table" which is 50°F

The engine is considered cold before ECT has reached the temperature upon which auF63635 == 1.0 at the lowest load. Eg 50°F according to this calibration KR3A-14C204-BKE (same as 15-17) as this is when the wideband is considered usable for closed loop operation.

Eg when MID63525 "Engine is too cold to run closed loop stoich." is set to 1.

Note: This is a work in progress and has identified some descriptions which will be updated as a result

 

[engineermike]

This is great info!

Any idea how auf41603 might play into this?

[Roland@pcmtec]

On 11/8/2023 at 1:14 PM, engineermike said:

This is great info!

Any idea how auf41603 might play into this?

On my phone. Could you post a picture and the description? 

[engineermike]

The description is "Minimum power demand enrichment time delay to engage the LAMBSE blending algorithm (torque smoothing feature), seconds."

[Roland@pcmtec]

On 11/16/2023 at 10:30 PM, engineermike said:

The description is "Minimum power demand enrichment time delay to engage the LAMBSE blending algorithm (torque smoothing feature), seconds."

It is for the blending delay from OL (1.0) to whatever your WOT lambda is. Generally people heavily reduce this so that you get WOT lambda immediately.