Can pulling too much timing cause knock?

[schpenxel]

Another frame or two forward, does it do anything different or stay basically like that?

[jtrosky]

Nope, stays like that. Same for all KR in log - the final timing never seems to reflect the KR. I've attached the log (it's pretty short). This particular KR starts @ frame 45766..

[jtrosky]

So this begs the question.... Is this KR even really pulling timing at all when it occurs? Or is it possibly just "calculated KR", like @GHuggins as mentioned and it's not really pulling any timing becuase of it? Although, why would they even "calculate" KR if they weren't going to pull timing becuase of it?

So confusing! :-)

I'm assuming that the timing PID just isn't working "correctly" for whatever reason and that the ECM really is pulling timing. But that is obviously just a complete guess. I mean how could I really know for sure?

[schpenxel]

Nope, stays like that. Same for all KR in log - the final timing never seems to reflect the KR. I've attached the log (it's pretty short). This particular KR starts @ frame 45766..

Weird!

[jtrosky]

So I logged another drive to the pizza shop yesterday (told you that I eat A LOT of pizza!) - I'm still seeing up to 9 degrees of KR at times (very rarely - mainly just one quick spike, but still). The good news is that on my drive back, I got into the throttle a little and had no KR under heavy throttle while in PE. So it mainly seems to be an issue during lower-throttle, lower-RPM situations.

For my next test, I've decided to try and desensitize the knock sensors slighly (multiplied by 1.05) between 0-2000 RPM (as suggested by @GHuggins earlier). I'm curious to see if this makes any difference. I feel a little better about doing this after revewiing the 2012 Camaro (same LFX V6) stock tune file and seeing that it's 0-2000 RPM knock sensors are *way* less sensitive than my Impala. Even after adding 5% to my sensor threshold multipliers, mine are still way more sensitive that they are on the Camaro. Dependiing ont the results of this test, I may also try setting them to the same values as the Camaro - we'll see.

Will report my findings... I work from home 95%+ of the time now, so the car just doesn't get driven like it used to - so takes a while to get logging done. :-)

[jtrosky]

Just a quick update. Things have been looking really good since I desensitized the knock sensors slightly for 0-2000rpm (still considerably more sensitive that stock Camaro LFX tune though). That really filtered out a lot of the "false" KR at 1200/1600rpm during very low throttle/RPM situations.

Also, fuel trims are generally looking a lot better too. LTFT's are almost always between +5% and -5% now - mostly close to zero.

So far, I'm actually really happy with the results from the few minor tweaks. I also put some DuraLube Severe Fuel System Cleaner in the tank the other day, so maybe that is having a positive impact as well.

Thank you to everyone that provided input along the way - will keep monitoring and report back if/when anything changes.

[jtrosky]

I know that I said that I would keep monitoring and report back only if something changed, but I had to provide another update with things continuing to work so well - which is a good thing!

Another drive to the good 'ol pizza shop today (I'm going to turn into a pizza!) - a drive that includes both low-speed back-road as well as high-speed highway driving, where I would *consistently* see KR values of 7 degrees or more. During the drive today, things were considerably better than they have been in the past. The most KR I saw was 4 degrees and it was just a single, quick spike that quickly returned to 0 without any change in throttle.

Either the knock sensitivty decrease below 2000 RPM, the fuel system cleaner or the minor MAF changes - or more likely, a combination of them all has really made a significant difference in the amount of KR I'm seeing.

Again, thank you all very much for hanging in there with me for such a minor issue! :-) So - any opinions as to which of the few minor changes made the most difference?

[GHuggins]

Sensitivity....................................... .................................................. .................................................. .................................................. .................................................. .....................?

[jtrosky]

Damn is my car running good now! I think that I finally got that "magic" combination of shift points, torque mgmt settings, driver demand, etc, etc, etc (fuel system cleaner and new ported throttle body may have contributed as well!)! I just went on a 3 hour drive with all sorts of road types and driving speeds and the throttle response is awesome, the shift points are just about perfect (might need to make 1 or 2 small tweaks), KR is minimal and everything is "just right"!

Thanks again for the help eveyone. It's amazing how miuch differecne a modifed driver demand table and modified shift points can make to the overal driving experience! :-)

Happy camper now!

[00GrcyGtr]

lol. Nothing wrong with that! I guess I should have included V/6's in the mix. And yeah, sometimes the good answers aren't in the places you would expect them to be in. Good luck!

Very good answer, I'm finding this a lot.