LNF Question regarding timing. Logged

[JAHSMITH]

Question for those LNF gurus. I am currently doing logs of my current tune. **Attached below

I am running a custom tune (20 psi on oem k04) on a completely stock 2009 Cobalt SS. I have achieved as high as 17 degrees of timing advance on several runs. In the log attached, on my final pull I saw 3 degrees of knock. Looking at the given log below, do you believe this to truly be the engine pulling timing or burst knock? All input welcome!


Hardest Pull.hpl

[GHuggins]

IMO, your idling at very low timing both during cold start and while hot - especially during a cold start - way negative. You might want to "tweak" your cam and OS tables in the idle areas... I wouldn't worry too much about any KR as from what I've seen, it's mostly usually false on these...

[codename Bil Doe]

Basic rule of thumb, if the engine is above 190? and the kr occurs when you're wot and the timing dips at the point of kr it's prob false. Bump the timing table up a degree at a time in the cell for which that rpm and load where the timing dip occurred corresponds to until the dip is gone. Hand smooth around the bump in timing. The kr will be gone.

[JAHSMITH]

IMO, your idling at very low timing both during cold start and while hot - especially during a cold start - way negative. You might want to "tweak" your cam and OS tables in the idle areas... I wouldn't worry too much about any KR as from what I've seen, it's mostly usually false on these...

Thank you for your advice, might you screen shot or reference where these tables are?

[JAHSMITH]

Basic rule of thumb, if the engine is above 190? and the kr occurs when you're wot and the timing dips at the point of kr it's prob false. Bump the timing table up a degree at a time in the cell for which that rpm and load where the timing dip occurred corresponds to until the dip is gone. Hand smooth around the bump in timing. The kr will be gone.

Thank you for the insight

[codename Bil Doe]

For fun to see what the Bosch ecu does and for better understanding, log from a cold start. When driving with ECT below 180 deg the kr will mirror pedal position. From 180-185 deg it stops mirroring but will input 3deg of kr and hold. It'll slowly drop off. From 185-190 deg it will input 3deg of kr with pedal and immediately step it down to zero. 190-195deg it will do the same but usually with only 1.5-2deg of kr. Above 195 false kr will appear any time there is a drop in timing with constant pedal position. This includes part throttle as well as wot.

[GHuggins]

For fun to see what the Bosch ecu does and for better understanding, log from a cold start. When driving with ECT below 180 deg the kr will mirror pedal position. From 180-185 deg it stops mirroring but will input 3deg of kr and hold. It'll slowly drop off. From 185-190 deg it will input 3deg of kr with pedal and immediately step it down to zero. 190-195deg it will do the same but usually with only 1.5-2deg of kr. Above 195 false kr will appear any time there is a drop in timing with constant pedal position. This includes part throttle as well as wot.

So my suspects of it being temperature sensitive are correct... How would you recommend going about getting rid of the logged false knock all together? Or is there a way to get rid of the false knock? Only way I've found is to raise the torque optimal spark, but it still logging false knock even with that - it'll hit the desired timing, but still shows up to 3 degrees retard with wot pulls...

[codename Bil Doe]

OS has nothing to do with false kr. Read the thread on OS.

Reread my first reply. For part throttle or steady-state throttle, find the point at which the kr occurs. If there is a corresponding dip in timing, raise the timing a degree at a time at that load and rpm cell until the timing logged is completely flat. Do this for anywhere that timing dips before recovering to commanded. This will eliminate false kr. Remember to smooth the timing table after raising timing.

Also read on OS and how to adjust timing so that you don't change the OS table. Don't blindly change timing without also modifying OS.

[califcarm]

Looks like your timing is aggressive for completely stock (I am completely stock). Not crazy, but right on the edge. I am betting that is real knock response, although it did not look like it was pulling timing (but I don't think that means there is not some real knock response going on, just not enough to cause the ECU to react to it).

I would pull 2 degrees of timing out of all the high load cells (180-200 from 2500-6500rpm) and log again. If the knock goes away then it was real. If you are not tuning yourself, then increase your octane by 3-4 points (NOS Racing brand octane booster will do that for you, but watch out most other brands do not work worth a crap) and log again and see if it goes away (again, real if it does). You had KR I think 4 or 5 times in that log at WOT. One time was for 2 full seconds over 900 rpm range. Not saying it is dangerous but my guess is it is real. You did not show timing dips at the point of knock, so I don't think that is it. Just think it is a little too much boost/timing and you might need to back off just a touch.

edit: if it is real, I don't mean to indicate that you need to stay with 2* reduced across the board. You might only need to reduce in a few rpm points, as that might be what initiates the knock and then it persists for a while. I had knock that looked like yours and just reducing timing by a tiny amount at 3500-4000 rpm I was able to get rid of all of it that was also happening at 4500-5000 rpm.