Look up other threads with this same problem it. To my understanding pay attention to the knock sum's but don't take it to heart. Mostly monitor the other vitals like DAM and the other knock sensors.

 

I wanted to reply here before starting a new discussion. I have a similar question. I took a random datalog the other day, since I'm a glutton for punishment I guess. Seriously though, parameters look great except for something that is confusing me. What is with the knock sum in Cylinder 4? The DAM, FBK, FKL remained 1, 0, 0 respectively for the entire drive as well as for the entire pull. I don't have data for knock sums as I do not monitor them on screen, but it stayed at a constant of 30 for the entire data log. The cells highlighted in green show zero variation for the duration of the log.

 

I would suggest reading through the Subaru Knock Monitoring guide on Cobb's website. Knock sum is a value that increments even when the event cannot distinguish between a knock event and engine noise. It can increase during idle but it doesn't decrease or reset until you turn off the car I believe.

From what I know the knock sum can hit values over 100 and still mean absolutely nothing. I don't monitor it personally and only use it if I am trying to investigate something.

 

I am seeking a tuner at this point but interestingly my DAM is at .938 yet the car is adding timing with positive values of feedback knock (I think that’s what that means)
I read through their guide twice and I understand a little better now but I want someone to take an in depth look.

 

It will add timing only after DAM has dropped, once DAM gets back to 1 you won't see those positive numbers anymore. That is completely normal. You might have just gotten a bad tank of gas.

 

this happened to me the other day as well when we had that bad winter storm and really low temps. I have just refilled with some shell 93 and the dam was 1, then dropped to .938 and started adding timing back lol. I may just run a 91 tune on 93 gas and see if this madness will end.

 

You can always use the AP to drop global timing by up to 3 degrees and see if that reduces knock timing retard.

 

What did you call me? Lol just kidding.
I have a small bottle of “octane booster” left from the other day and so I just threw that in there to see if it would change. In a hundred miles or so if nothing is different I’ll drop the timing manually.
If it doesn’t change then.. idk. I’m about to in plug the AP and start smiling again and if it grenades itself, whatever.

 

Yea, the knock monitor while helpful can cause some serious paranoia if you try to focus on it as a complete measure of the health of the engine - it is going to adjust and you will have some detonation there is no avoiding it.

I usually keep track of how many miles it takes to get back to 1 and that can vary quite a bit (I try to make sure I drive easy and empty the tank as much as possible before filling up again just so whatever issue it was in that tank is the smallest percentage of the new tank that I can make it)

I have had as short as 20 miles and as long as 180 miles over the years according to my spreadsheet I keep 🤓 Depending on where you live and how the fuel is sometimes it is worth dropping to the 91 map to see (I live in the pacific northwest and we generally have 92 everywhere so I had always used the 91 map) and I also would say that winter gas in our area I usually saw a higher occurrence of DAM adjustments compared to summer months. Not sure I can statistically prove they were all gas related or if some of the additives change in the winter that would cause that or not though.

 

thanks that makes me feel a lot better. I did 5-7 pulls last night logging with the dam at .938 and it never budged but everything else was awesome. 0 knock learning. Positive feedback knock.Car felt great and ran great so I’m not going to sweat it unless it starts going backdown or running poorly. Like I said earlier, I’d rather have fun with the car and smile than let it become a burden. If I need to rebuild it. Whatever.
I also understand your spreadsheet enthusiasm. I’m building up quite a nice setup myself😂