[LeadHead]

So I've been helping my buddy tune his turbocharged F-250 for a few years now, using a HOG1 EEC-IV (AHACB strategy) and SailorBob's def.

One issue I never noticed before (mainly because we've never done it), is that doing a boost launch, or flooring the truck from a dead stop, the ignition timing would lock at 0* according to SAFTOT and hold there until the truck started gaining some speed. I then checked the spark source and found that it was coming from "Transmission Gear Torque Truncation". I did some digging and found that there is a table that specifies a maximum torque in each gear (FNTQ_MAX), but the problem is the table maxes out at 1020 lb-ft, which after torque converter multiplication is only around ~500 lb-ft at the engine. Not a lot for a turbocharged V8.

The only way I could find to get around this was to zero out FN799, which is "Spark MBT Retard for Torque Limiting". Zeroing this table fixed that issue, and we actually have low-end power now. However, zeroing this table also removes torque limiting during shifts, tip-in torque reduction, which is fine since the transmission is built. The bigger issue is that FN799 is also used in "Determining feedback spark idle control spark advance according to the desired torque ratio to be supplied by the engine." So I'm pretty sure that means the feedback spark idle control has effectively been disabled.

So my questions are:
Have I inadvertently disabled idle spark feedback control? Is it a big deal? Is there another way around the transmission gear torque limiting (maybe set it to a negative value or something?) without zeroing FN799?
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Now Part 2: On to the borderline table. We've had very little actually dyno time to dial in spark, so we setup the spark borderline table based on the stock table, just with the upper cells reduced some. Now I recently found a copy of the "HOG0" calibration, which is the same AHACB strategy. The HOG0 and HOG1 calibrations were both for the same engines, during the same model years, for the same emissions zone (California). They're very similar, except HOG0 has a much more aggressive spark borderline table than HOG1.

Shouldn't these tables be the same? Why did Henry chop a bunch of spark out of HOG1? Some emissions reason or something? Do you think it'd be the safe to base our spark table on HOG0's more advanced timing? Our spark source almost always seems to be using the borderline table while driving, and I feel using the HOG0 table would probably bring quite a bit more responsiveness to the engine.

Here's HOG0:

hog0.png (49.57 KiB) Viewed 4937 times

Here's HOG1 (ours), you can see how the mid range basically has anywhere from 4-9 degrees of timing taken out - the high end has around 3 degrees removed and high load/low RPM is running as low as 0*:

hog1.png (68.75 KiB) Viewed 4937 times

[LeadHead]

bump

[LeadHead]

No one knows anything at all about these transmission functions and torque limits..seriously?

[95GTSpeedDemon]

ever found a fix/answer?

im dealing with a s/c f150 with the same def and im seeing spark and lambse different than what my tables are.

[sailorbob]

Setting the 'Torque Limit for Gears' (aka FNTQ_MAX) values to their maximum should eliminate torque truncation. The returned value is checked against the calculated transmission input shaft torque with the 'Torque Truncation Flag' (aka FLG_TQ_TRUN) only getting set if the returned value is less than input shaft torque.