Is there a Fuel Trim Cell table?

[VFL77]

In my effort to self edumacate and understand why I get random knock at 80-100km/h (50-60mph) cruise, I've discovered it almost always (>95%) happens when I'm in Closed Loop Fuel Learning/Fuel Trim Cell #9.
Is there a table relating to Fuel Trim Cell visible in the Editor for an E38 ECM that might be connected with why I'm getting knock?.
Is monitoring this sensor of any value?.

The attached is typical and occurred while doing a VVE calibration at 12.5 AFR.

Piccy_06 2018.05.21 20.26.gif

[07GTS]

check which retard u are using there are a few and some are just any type of retard (or spark retard) that may not even be knock related, i monitor "knock retard" in mine then i know its coming from the sensors, u are in PE with light load and timing isnt high at all for that situation so it seems like its false if u are monitoring actual knock

[VFL77]

I have disabled Burst and Static retard options and the KR on the graph is real since I can hear even more knock than what's in the scanner (XForce LT headers...1 3/4, 4->1). 'Knock Retard' has the same value as 'Total Knock Retard'.
I'm not in PE, I've set the OL EQ to 1.174 which is the max setting i have in PE. This way I don't worry about PE kicking in and I can disable transient activity to try and narrow down on 'true' VVE calibration (and what's really happening with KR). For all the world it seems like the motor just knocks under these load+RPM conditions even with 98 octane (AUS). Motor is unopened L77 w/auto with CAI and exhaust, if you've got a tune that would indicate I have a motor issue, I'd appreciate it. I have the same behaviour even with the stock tune loaded.

[07GTS]

do u have flex sensor ? see if it goes away with e85, whats it like at stoich ? same deal or more/less knock

[VFL77]

No, it's the last of the Holden L77's so no Flex (DOD only).
Appears to be same behaviour at stoic - no better or worse - just intermittent knock at a certain load-rpm point which is right in the middle of normal cruise speeds. I really expected the issue to go away by forcing a 12.5 AFR, but no change.
I'm now at the point of trying to work out what might make it go away even if I can't make that a permanent change, so I'm starting to play with richer AFR, different EOIT, more spark reduction etc and I'm already on my 3rd type of sparkplug (currently colder).
I had planned to swap the cam in future (and make the problem go away that way), but I've found a 'stock' L77 has more than enough power on short tracks for the available braking configuration and my skill level...

BTW, I've concluded that FTC #9 where the knock mostly happens is an output, not an input.

[07GTS]

might sound odd but try adding 10 deg spark to that whole area and blend back in, more torque can help at low rpm low load situations, also u can add all the individual cylinders knock 1-8 and then at least u can see which cylinder is causing it and even desensitize just the one in that specific area if its just false

[VFL77]

Thanks, I'll give the extra advance a go. I understand how extra advance timing should increase torque, but it's not clear why that would solve knock. Is it just because it changes the combination of settings that it's operating at?

I had already added the individual cyl knock settings back in for the next set of logs, but based on previous playing I expect all cyl will complain equally.

thanks, again.

[subsonic_79]

I agree with logging the individual cylinder knock retard, at least you may find some trend to a specific cylinder.

While the spark advance seems quite normal for that RPM and load point on your log, have you simply tried removing a few degrees in that area to see whether there is any change? I know this is fairly low load area, however I find these engines want quite low timing in the 1200-1800 RPM area during cruise.

[07GTS]

on mine i didnt have knock but if my timing was that low in that area it just wasnt enough for it just needed more torque, knock is an odd thing and can have many situations cause it too lean or too rich, too much timing, poor fuel ect, if u have it at stoich or with a richer afr and its still showing knock at that low load/rpm area then there just has to be something that it dosnt like or maby gets a vibration from headers/exhaust (resonance) causing the knock sensors to show, if its all cylinders then it seems odd its normally concentrated to an cylinder or area/bank (unless its bad fuel related), and your 02's arnt showing any signs of it missing or anything to cause knock

[vette_c6]

rule number when ,,
when you ask for help . upload your file and your scan so we can have a look

[VFL77]

More than happy to provide, but it's not much different to stock (other than all the bits that have been fiddled with).
This is with reduced spark Tune2-3-12b-VVE_v6.hpl Tune2-3-12b_VVE-v6_reduced spark.f.hpt
This is with extra spark Tune2-3-12b-VVE_v7.hpl Tune2-3-12b_VVE-v7_extraspark.hpt

[Tapout Tuning]

vette_c6, do you train Jiu-Jitsu?

[vette_c6]

im a judoka and i have done some jiu jitso fights got many medals in both

[ZeroBoostBuick]

1,550 rpm, 26% throttle and light acceleration is not unusual in some cars to see little bit of KR.

If you were just cruising at 1,500 rpm, little throttle and steady speed and seeing KR is a different story but still not a big deal to see a blip of 1* KR. Could be the gas for all we know.

[VFL77]

Could be the gas for all we know.

I wish, as that would make things so easy.
I've tried various fuel brands over time and only use 98 octane (Aus), and I've never seen the behaviour change even when using 94/95.
(I think our 98 RON fuel ~ 93 AKI fuel in the USA)

[VFL77]

FWIW, this is still unresolved.
I've tried spark timing, EOIT, airflow mode tweaking, sparkplugs, different air intake...
I'm at the point of blaming the header design, but I'd be surprised if even a great header design could cause much fuel to be lost out exhaust with a stock L77 cam overlap (does it even have overlap?, it's a pretty puny cam, but enough power for the braking capacity).
Oh, one thing that has changed (and I don't know when), but the FTC that generates most KR is #1 now, not #9.

Anyway, thought I'd post an update if anyone reads this in future.
(I'm not bothering to post the current tune because it's always being tweaked and only relevant for 2-3 days at a time)