smooth the fuel map between rpm changes. Make smaller jumps.

 

I have the same issue with my car right as it hits 0 vacuum when I'm at part throttle. I've tried dropping timing and adding fuel (even as much as up to 8 degrees and smoothed it out) and it still picks up 3-4 counts. I haven't tried adjusting the crossover point just yet, but I'm starting to wonder if this is something mechanical being picked up like maybe a throw out bearing noise or something rattling.

 

I gave up on the same problem a year ago. Tied xylene and even spraying methanol that early but no change. It's just the sensitivity of the filters and lack of background noise, probably valvetrain noise picking up on the mic

 

It's probably possible, but today was a nice warm day for a change and I noticed that every time I feathered into the "0" range it showed over 3 counts of knock near the 3000rpm range on the highway. It does show over 3 counts once and a while when it's cold out, but definitely not as much as it did today. Because of that I'm starting to rule out the phantom noises as being the cause, but I'm not sure I understand why it would do it especially when I've toned down the timing before and upon entry to boost pressure and even went so far as to lower the lean spool afr right before the 3000 rpm mark so it sits as 12.5afr once I start to hit that crossover point.

 

It can be as high as whatever ignition timing map is + BE ign adv/ret #2 value is for the respective load/rpm. For exp: 38* + 6* = 44*. The reason for this is for emissions and the required advance during exhaust dilution.

I set my BE ign #2 table to 0* throughout, the ign advance now correctly corresponds directly to the ignition map, and better yet - part throttle knock has dropped down to no more than 3 counts.

I think the dilution advance is helping the emissions but at the same time creates surface CHT's that are not severe enough to spike cyl pressures, but provide enough for autoignition chemistry as charge and fuel are ramped up (part throttle)

Just found this out yesterday when I decided to pull out the adv in the BE map for the hell of it.

 

that is really an interesting observation - I will try it if this part throttle knock will get worse with the increasing outside temperatures these days.