steadfastWRX

I've got a 2014 wrx 5dr which I've loved since the day I got it. Broke it in fine and never really "beat it up" in my mind. But after going from cobb stg 1 to tp stg 1 with turbo xs intake I've notice the car over boosting just a hair around 18.6psi and it's set for 18psi. Runs fine but less of a pull in 3rd since the original tune. So getting into the app and data logging I notice my knock sums are getting a little out of hand it seems on cyl 2. A 30 min drive threw traffic showed about 38 when I parked. They are happening at the most random moments and sometimes under load but rarely. Just looking for an explanation I see a lot about cyl 4 knocks but not about cyl 2. Other cyl have 1-8 total knocks. Fbk and fkl are normal with what seems like a ghost knock every now in then at low rpms and shifting. Should I do a compression test or leave it be?

Alex Rodriguez

Hi. I had the same concern and this is some information I have read about in different forums and sources.

You should monitor Feedback Knock and Knock Learn parameters. Those are the ones that would really notify if there are continuous timing retarding factors such as real knocks.

Knock sensors are basically microphones and when monitoring knock sensors on each cilinder is normal to get a lot of noise specially on subarus. Cylinder #4 is usually the closest to something, not sure if exhaust or what, but it is normal for everyone to report a lot more noise than the other cylinders.

Basically, if any noise is captured, the knock increase in that cilinder. but if there's important knock noise, which leads the ECU to retard timing, you will see it in the feedback knock or fine knock learning. Another paramete you can monitor is the DAM.

If DAM is 1, and Feedback knock and Fine knock learn is 0, you will be OK. you can ignore those cylinder knocks reports.

if there is significant knock happening those numbers would be moving fast as a counter, and not randomly.

I am not a professional of AccessPort or COBB, but I am sharing with you all the info/knowledge I got when I had exactly the same doubt as you.