Weird knock detection L98

[space387]

I have been working on the tune for my 1990 Corvette and have found that it shows a knock detection at 1600-1650 rpm. I can not seem to identify what is causing it and have tried backing off the spark table to counter it with no avail the knock retard remains at the same value. This is only at 70mph, 2mph lower or higher the spark magically disappears. I'm not sure how to combat this. Any help would be appreciated.

[NomakeWan]

If it’s at a specific speed at a specific RPM it sounds to me like it’s resonance causing false knock. Combatting that would be difficult as you would need to find the source and dampen it (may be impossible), would need to dampen the knock sensor (Teflon tape on threads; this however reduces overall sensitivity of the sensor across the board), or would need to create a new ESC profile (dunno about a ‘90, but on $EE this is currently not possible due to lack of reverse-engineering of the ESC module).

Best of luck.

[space387]

Thanks. I have seen this before where I had set the distributor wrong and the car was running with about 10* less timing than is should have but I could feel when it would pull down to about 12* actual timing leaving me with no power to pass 70mph in 6th gear. I have been very active with tuning so maybe I will try leaving the knock detection active just remove the retard ability while I tune allowing me to interpret the events.

[84Elky]

Space -- Please upload a .csv file of your log. Without knowing your ECM mask and having a matching ADX, your xdl log cannot be properly analyzed. You can see only 1 view of your attachments -- mine.

[space387]

ADX and XDF have been updated

[84Elky]

Knocks could be from transient vibration. But look at the 'Knock Count & Retard' Tab of the attached Analyzer. Analyzer tells you everything. Some things not shown because you're not using S_AUJP. See also attached .xlsx exported log.

Very high SA-TDC reported. Unless you have aluminum heads, this is way too high and even then questionable. You'll also note knocks occurring when the engine is not under any significant load other than WOT (ie - kPa generally < 70). That's not knock territory. I'd reduce entire spark table 5-6* at 1000 RPM all kPas and see what happens. Gotta start somewhere.

Other observations:
- o2 sensor randomly reporting not active causing open loop. See highlighted samples at 2880, 5166, 5457). This is due to bad connection or failing sensor. It's not due to not being heated or high enough temp because it is active during most of idle at end of log.
- Your idle TPS% needs to be reduced. Code assumes idling only when when TPS < 0.78% and MPH < 0.9. This affects IAC positioning. Voltage = 0.60% at TPS%=0 is best.
- Also note at sample 24723, TPS% randomly begins to drop to 0% while voltage does not change. These type of oddities are generally due to bad grounds or an inadequate connection somewhere.
- Additionally, you'll see that idle spark at sample 24720 drops significantly below the 20.04 degrees in your spark table.

Bottom line, a bad ground or connection somewhere could also be causing the knock retard, which may not really be occurring but is being reported as such.

All other info looks OK. But cannot rely on BLM data in Analyzer because of all the random OL samples.

HTH, Elky

PS ---
Really need to upgrade to S_AUJP. Conversion is painless, will take 10-15 minutes and you'll be using your exact calibration as now, plus will have access to every calibration item in BIN via XDF and will be reporting everything possible providing better analysis.
Here: https://www.thirdgen.org/forums/diy-...-released.html