Preemptive feedback knock correction

throttlehappy · **Posted:** Wed Sep 19, 2012 9:16 am

I have narrowed it down to a few 'triggers'

* Engine g/rev or g/sec increasing rapidly in under 250ms(believe I found the timer value near the PEKC retard value)
* Total Ignition timing values changing by more than 3 degrees with some sort of g/rev and rpm reference(I suspect a 3D table controls this?)
* Boost AND vacuum error

Heide264 · **Joined:** Sat May 07, 2011 3:22 pm **Posts:** 144

td-d wrote:

I've not had the time to really dig through this, but I suspect given feedback (excuse the pun) above, that it is the same as this value referenced by COBB:

Feedback Knock Retard Decrement Alternate (Max. CL Target Rich)
-> This value is the step value for each negative change to feedback knock correction when the maximum closed loop fueling target lambda (which changes based on various conditions) is at the "rich" maximum.

So I expect that if I had to follow the logic of the various switches checked prior to branching off to this alternate value, they would relate to CL fueling lambda.

Not convinced that it's preemptive in that case...

Keep in mind I have CL Fueling completely disabled =/.

STiLYN · **Joined:** Mon Apr 16, 2012 10:29 pm **Posts:** 6

throttlehappy wrote:

I have narrowed it down to a few 'triggers'

* Engine g/rev or g/sec increasing rapidly in under 250ms(believe I found the timer value near the PEKC retard value)
* Total Ignition timing values changing by more than 3 degrees with some sort of g/rev and rpm reference(I suspect a 3D table controls this?)
* Boost AND vacuum error

Are these the Triggers you wanted to test on me by turning off my Feedback knock correction ??? :roll:

throttlehappy · **Posted:** Thu Sep 20, 2012 6:38 am

STiLYN wrote:

throttlehappy wrote:

I have narrowed it down to a few 'triggers'

* Engine g/rev or g/sec increasing rapidly in under 250ms(believe I found the timer value near the PEKC retard value)
* Total Ignition timing values changing by more than 3 degrees with some sort of g/rev and rpm reference(I suspect a 3D table controls this?)
* Boost AND vacuum error

Are these the Triggers you wanted to test on me by turning off my Feedback knock correction ??? :roll:

Look at your FLKC in your temporary tune which was there to pull timing permanently in a wider rpm and g/rev range IF true knock existed to show you it was not FBKC... I tested it on my own car and that one tune you got was to show you that the figure being pulled was NOT the FBKC value. Funny that even Cobb pointed out that FBKC was 'normal' :wink:

You are also aware that forged motors are inherently more noiser as well and yet your knock counter never moved

Easty · **Posted:** Sat Nov 03, 2012 10:23 am

I believe i have found the switch that activates PEKC but i can't find where this value is set/cleared any tips on finding it? Indirect addressing makes things very hard, my rom is AZ1G400W.

td-d · **Posted:** Sat Nov 03, 2012 10:31 am

Have you tried the 'control R' trick I found?

Easty · **Posted:** Sat Nov 03, 2012 11:01 am

Quote:

Have you tried the 'control R' trick I found?

Yes i have its very neat! but unfortunately it won’t help me find this particular ram parameter that is being set in code somewhere through indirect addressing
.

dschultz · **Posted:** Sat Nov 03, 2012 2:07 pm

Easty wrote:

I believe i have found the switch that activates PEKC but i can't find where this value is set/cleared any tips on finding it? Indirect addressing makes things very hard, my rom is AZ1G400W.

Where (address) in your ROM are to looking now at the switch?

wrxt4cy · **Posted:** Sat Nov 03, 2012 8:50 pm

Can I get the address for AE5K611V (2012 USDM STi).

I was tuning one today with a Cobb short ram intake and was seeing a lot of what seems to be PEKC starting around 5000 rpms in a pull. Boost/Timing/AFRs were spot on. The only thing that seemed odd was that the intake temps were rising pretty rapidly from the start of the pull to the point where the PEKC occurred. This intake seems to suck in pretty hot air and it seems like the rapid increase triggers PEKC. I know its not normal FBKC because like before, I pull a different value than 1.4* and I'm seeing 1.4 in the logs.

Do there appear to be any triggers related to intake temp deltas?

He's putting the stock air box on and we're going to retry tomorrow to see how it behaves.

Thanks.

Easty · **Posted:** Sat Nov 03, 2012 10:40 pm

Quote:

Where (address) in your ROM are to looking now at the switch?

FFFF76CE Pre_Emptive_FBKC_Switch

td-d · **Posted:** Sat Nov 03, 2012 11:12 pm

Easty wrote:

Quote:

Where (address) in your ROM are to looking now at the switch?

FFFF76CE Pre_Emptive_FBKC_Switch

Yup, that's the r13 variable that splits off the routine in the rom I was looking at as well - the question is, what sets it? And also, it activates the alternate value when the switch is zero... My gut feel is still airflow.

Easty · **Posted:** Sat Nov 03, 2012 11:37 pm

Quote:

Yup, that's the r13 variable that splits off the routine in the rom I was looking at as well - the question is, what sets it? And also, it activates the alternate value when the switch is zero... My gut feel is still airflow.

I think your right but It's like trying to find a needle in a hay stack!

As throttlehappy said over in the Injector Flow scaling thread it could be something to do with this table

Attachment:

Untitled1.png

The values in the table do look like they could be MAF/gs so it posible......

td-d · **Posted:** Sun Nov 04, 2012 12:05 am

Easty wrote:

Quote:

Yup, that's the r13 variable that splits off the routine in the rom I was looking at as well - the question is, what sets it? And also, it activates the alternate value when the switch is zero... My gut feel is still airflow.

As throttlehappy said over in the Injector Flow scaling thread it could be something to do with this table

The values in the table do look like they could be MAF/gs so it posible......

Not seeing any reference related to FBKC anywhere near this table - but it's associated with a value that is multiplied by the engine load comp table values elsewhere.

MFB · **Posted:** Sun Nov 04, 2012 12:06 am

Data looks like requested torque

Easty · **Posted:** Sun Nov 04, 2012 12:20 am

Quote:

Data looks like requested torque

I suspect Subaru intended "requested torque" to be requested MAF, in a rough sense.

Quote:

Not seeing any reference related to FBKC anywhere near this table - but it's associated with a value that is multiplied by the engine load comp table values elsewhere.

I haven't found any Link between the two yet either

RomRaider

Preemptive feedback knock correction

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