Spark timing torque control issue

[engineermike]

My Whipple 2018 Mustang actual torque suddenly increases 30-40 seconds after startup and I am trying to determine the cause so I can tune it out. The spark timing increases suddenly by 7 to 15 deg, NOT coincident with it coming out of CSER mode. At this time, the spark source is "Torque control" (Timing = Torque Mgt Advance) then switches to Base/MBT. Based on the spark source and the fact that I can't seem to align it with any thresholds in the Spark Base Emissions Reduction tables, I am led to believe it is torque management related. In the attached log, it happens at 00:46:332.

Any ideas what this is and what I can do to smooth this out?

Thanks,
Mike

[murfie]

Idle is targeting an RPM. anytime accelerator pedal is 0, it targets idle. Its always goes to the table with the lowest spark value. For idle this usually ends up being MBT value, once all the emissions reduction/ Cat warm up stuff has done its job they usually go to 55* at their maximum run time values and become one of the higher spark values at low rpm/low load. MBT is usually more spark than is needed to maintain the desired idle RPM, so it resorts to torque ratio and torque spark control in a PI torque loop to get to a lower spark value that gives the desired RPM. Coming off idle, the spark taken out by the torque control is put in before the actual throttle is opened to meet the drivers demand quickly. from 25-46seconds this is what you are seeing when you press the accelerator pedal.

Under torque management> general> torque ratio> spark delta model you will see that from 1 TR to .98 TR you can have a 6-8* jump at low loads. With 17* being MBT, 5* of spark probably doesn't represent 2% of the torque at low loads. Its a little aggressive in and out of TR control or your MBT values are too low for lower RPMs. Middle of the S curve instead of at the top near true MBT.

[engineermike]

Not sure if relevant but I’m not at idle when the sudden power increase happens.

I tried the following with no discernible effect on the issue:
- set cser spark torque ratio to all 0’s
- set cser spark torque ratio to all 1’s
- set cser base drive spark table to all 55’s
- set cser spark adder to all 55’s

It appears to me that the supplied tune (mainstream aftermarket) set up an intermediate Mapped Point for the purpose of smoothing out this transition but it doesn’t work quite right. The ER distance table and index array have it starting at MP14 (0,0) and moving to MP15 (30,0) as it warms up. They added MP12 (20,0) (plus snap to lines) as a pass-through. It seems to be right over MP12 (and heavily weighting it, as such) when it comes out of cser mode. My MP12, as supplied, has some abnormally low MBT numbers in the low speed-load range I can only assume are there to ease the transition out of cser. If this is correct, then it seems like a poorly designed bandaid. I could probably play with the MP12 MBT table to smooth the transition but this is only upgrading the bandaid.

Any guesses as to what table might be off to cause this abrupt spark transition out of cser in the first place? I was thinking cser spark adder or delta spark torque ratio, but these tables appear to be untouched from stock.

[murfie]

Each spark source spark value is being calculated all the time. The lowest value from them all is used. If the lowest value translates to too much torque, TR steps in and reduces spark further. You want to get spark control to a specific source in a ford lower values till it uses that spark source. Raising values excessively is never what you want to do to gain control over spark, it will just go to the next lowest source, and unless you really pay attention to all your spark sources in the calibration, most people will not know what the next lowest source will be. Small changes and watching sources will help you figure out how to gain control.

You are not getting spark from cold start emissions reduction base table, so TR value changes to that won't do anything. I figured The values in the CSER base tables were probably higher than MBT, as it was what it went to out of torque control, instead of starting low and increasing with engine run time like stock. I also know this as your spark source shows you its coming from torque control right from the start and not 90-150 seconds after startup. Normally CSER is low spark and takes time to increase too a value higher than MBT, at which point it goes into torque control after its been running for a little while. Its called cold start, but its on every start with engine run time. This is essentially how cat light off works to warm them up and reduce emissions. With them gone you no longer need the low spark values, between this "raise it out of the way" practice and then butcher the MBT spark to control idle RPM flare, you are not controlling idle spark properly.
I mentioned MBT being too high at idle to meet torque request for desired idle RPM so you understood how idle torque control works. You had come off idle, I saw that, I also said to meet your request the spark taken out from torque control gets put back in as its the fast method of meeting driver demand torque increase. Idle should be controlled with the torque/inverse tables and achieving a good 0 ETC torque(EBT should be equal to this)/ scheduled torque difference, the "idle torque". This can be anywhere from 40-70ftlbs and the relationship should maintain all the time at all pedal positions and RPMs with only very slight variations in transients. Its how you get good return to idle with out stalling or hanging. You don't want 70 at idle, and it dropping to 40 off idle or vise versa. You want it to always know what its returning too. Keep in mind torque/inverse is based around stoich, MBT, and STP. Torque ratio reduces the commanded spark starting at MBT=1, to meet idle RPM. Spark torque reduction is an S curve. Translating 2% of torque to 5-8* spark delta at the top of that S curve is a lot at lower MBT spark values. MBT is only a low value at higher loads/ low RPMs. Low loads its normally high 20's low 30's, and 5* with that much advance already isn't going to make much difference in torque.

[engineermike]

In reading your response, I wanted to clear up a few things:
- The issue only occurs when it transitions out of CSER.
- As far as I know, it has never happened at idle.
- I wouldn’t call it an idle flare because it only happens once in a drive cycle and only with the engine cold and not at idle.
- I increased the CSER values to 55 as a test to see if that was causing the low timing values during CSER. It wasn’t.
- I still have cats and intend to keep the CSER functionality. I just need to understand how timing is being controlled so I can fix the transition out of CSER.
- I understand butchering the MBT table to smooth this transition out of CSER isn’t the right way to do it. I was intending to point out it’s how my main-stream tune had it. I guess they could t figure out a good way to transition out either.

So in sequence from my log, it repeatably does the following in the first 50 seconds of run time:
1. Start
2. Running in CSER fueling mode. Spark timing settles in the negatives. Spark source is torque control. Mapped point is emissions reduction (MP14-0,0)
3. Spark timing starts ramping up, still in torque control. Fueling still in CSER. Mapped point is moving to MP12-0,20. I’m no longer at idle, but driving.
4. At 40-50 seconds, Cht is around 110, cat temp is around 900. Simultaneously, CSER switches off, spark source switches from torque control to either MBT or Borderline. Spark timing instantly increases by 5-15 degrees and torque increases by 10-20%.

My assumption was that the spark timing limits imposed by CSER would be above MBT by the time the thresholds are met to turn CSER off. I was attempting to gain control of CSER timing by changing the CSER base drive table to 55’s. However, this change had no effect. I assumed the CSER timing is controlled by the CSER base drive and CSER adder tables in Spark, and maybe the CSER spark torque ratio in torque management. However, my spark timing during CSER seems to be affected by something else so maybe I’m missing a table.

[engineermike]

In case anyone else is looking for answer on this, I found a solution that works. Under Torque Management->General->Torque Ratio Clips->Upper (CSER), I changed the value from 0.86 to 1.00. Now, the spark timing ramps up to typical values before exiting CSER mode. Deep down, I know this is still a band-aid because every Mustang calibration I've seen uses 0.86 for this value. However, I'm also certain this solution is better than butchering the BKT and MBT tables and manipulating the Emissions Reduction Distance Tables to influence spark timing.

I still can't explain why populating all the Emissions Reduction Spark Base and Adder with all 0's or all 55's didn't seem to affect it. The Gen 2's seemed to find success with this. All I can figure is that the Gen 3's handle CSER spark timing differently, perhaps based on Torque Control rather than relying on the Emissions Reduction Spark tables.

[HellKnightHicks]

In case anyone else is looking for answer on this, I found a solution that works. Under Torque Management->General->Torque Ratio Clips->Upper (CSER), I changed the value from 0.86 to 1.00. Now, the spark timing ramps up to typical values before exiting CSER mode. Deep down, I know this is still a band-aid because every Mustang calibration I've seen uses 0.86 for this value. However, I'm also certain this solution is better than butchering the BKT and MBT tables and manipulating the Emissions Reduction Distance Tables to influence spark timing.

I still can't explain why populating all the Emissions Reduction Spark Base and Adder with all 0's or all 55's didn't seem to affect it. The Gen 2's seemed to find success with this. All I can figure is that the Gen 3's handle CSER spark timing differently, perhaps based on Torque Control rather than relying on the Emissions Reduction Spark tables.

Thanks I found this information helpful for something I was working on. Im no Ford tuner but I know my way around for the most part.