Subaru Knock Monitoring and DIT DAM Strategy Changes

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Subaru Knock Monitoring

Knock! Knock!  Who’s there?  It could be nothing at all, but, it may be cause for concern.  Knowing the difference can give you peace of mind, or, could be an early indicator of a mechanical issue ticking away on your Subaru.  Datalogging and monitoring with the Accessport can provide useful data on these knock events.  Couple that with some basic knowledge and you’re on your way to quickly and easily diagnosing any knock events at any given time.

First, let’s talk about what exactly “knock” is and how it’s detected by your car’s ECU.  Sometimes knock is also called detonation.  Detonation is characterized by the air/fuel mixture spontaneously igniting during the compression stroke.  The force of this early, unintended explosion is counter to the direction of the piston and results in a sharp increase in cylinder pressure.  The increased pressure can exceed the design limits and potentially cause damage.  These events typically result in an audible noise that can sound like a “ping” or “knock.”  The ECU picks up on this noise with a microphone hard mounted to the engine block and listens for specific frequencies that indicate a knock event.  Any number of conditions or factors can induce detonation.  The sources are varied but are generally due to increased cylinder pressure, high temperatures, or reductions in effective octane level.

Worried?  Don’t be!  Detonation events are inevitable and will occur from time to time on any modern vehicle running on pump gas.  Your car is built to recognize these events and take the appropriate action to defend against them causing any damage.  The Subaru knock detection system tends to err on the side of caution.  This makes it common to see “false knock.”  False knock occurs when the ECU corrects for a knock event but the noise registered is due to other noises that aren’t necessarily detonation or harmful to the engine.  This often happens accelerating from a stop while letting the clutch out, during gear shifts (more so if grunting while shifting), accelerating at low RPM in a high gear, under cruise on the freeway, and during abrupt throttle changes.


2011_Subaru STI_COBB 3

Relevant Monitors

There are times when these knock events are bad news.  Knowing which parameters to monitor with the Accessport can help determine if that’s the case.  Generally, Dynamic Advance Multiplier (DAM), Feedback Knock Correction, and Fine Knock Learning are relevant when monitoring knock.

  • DAM represents a global adjustment to ignition timing.  If this value is anything less than ideal, it’s a quick indicator something isn’t right (unless immediately following an ECU reset/reflash).  On an 02-05 WRX the values will range from 1 to 16, 16 being ideal.  On all other Subarus, the value is expressed as a decimal from 0 to 1, the ideal value being 1.
  • Feedback Knock Correction is a real-time timing correction the ECU makes based on a perceived noise.  The ECU immediately pulls timing (the amount of the Feedback Knock Correction value) and adds timing back (value rises to 0) assuming no further noise is detected.
  • Fine Knock Learning represents minor learned corrections currently being applied by the ECU as a product of historical noise. These values are reset if the DAM value is changed; once DAM has stabilized, any learned corrections will be intermittently evaluated for sanity when certain thresholds/conditions are met. Fine Knock Learning is learned (and thus applied) for specific ranges defined by load and RPM; once a correction value has been learned iinto a particular range, it will be applied whenever the engine is operated within that range.

In general, we consider Feedback Knock Correction ~-2.5 degrees or less to be “normal” and not of major concern.  If DAM is below the ideal value and there are corrections beyond -2.5, this is good reason for further inspection.  If these corrections occur during full boost and wide open throttle it is especially concerning.

Poor quality fuel is a common cause for knock.  If this is the case, and you’re running an OTS (off the shelf) map, try switching down to a map designed for lower octane fuel.  Switching to an “LWG” version OTS map may also help resist knock by lowering boost pressure.  Use fuel from top tier retailers in your area to ensure your effective octane is as high as its rating.

Common mechanical causes of knock worthy of inspection are worn MAF or front O2 sensors, boost/intake tract leaks, and excessive blow-by.  Definitely be sure to also read the map notes for your vehicle to confirm you have the proper hardware modifications for the map you are running.  These can be found on the website by configuring your vehicle and clicking the maps section.  Then, select your map and click the “notes available” link.  Also, see that you are within the boost range outlined in the map notes.  If overboosting is occurring,  knock may be more prevalent.



DIT DAM Strategy Changes

The newer DIT car’s (direct injection turbo – 2015+ WRX and 2014+ FXT) strategy is a bit more reactive.  This is intentional and is expected since “premium” fuel is not required on the DIT vehicles.  The strategy has changed and is comparable to what may have been seen as Fine Knock Learning in the earlier non-DIT cars may now result in a drop in DAM in the DIT cars. It shouldn’t be surprising to see a drop in DAM on the DIT vehicles (as it is on early cars where DAM being less than ideal is an indicator there is an issue) especially running lower octane fuels.  How long the DAM takes to return to 1 is not indicative of how serious the knock event was and does not mean the car is still knocking.  In order to advance the DAM on DIT vehicles, you have to drive in specific load/RPM ranges without knock.  Determining whether there is a a potential issue on a DIT vehicle requires considering how low the DAM has dropped and what other knock responses ( Knock Feedback Correction and Fine Knock Learning) look like overall.

Hopefully this post can help ease some concerns when you see those values under the knock parameters.  If you think your vehicle might be having some negative issue mentioned above, feel free to contact us and we can review datalogs, help troubleshoot, and answer any questions you might have.  Also check out our knowledge base for additional technical information on all things COBB.  If you’re interested in learning more about Subaru Knock Monitoring, check out this FAQ.

Subaru knock detection is like using a large net to catch fish. You’ll definitely catch what you want to catch (actual knock) but you will also catch what you don’t want (false knock). If you used a small net, you would get less false knock but might actually miss actual knock. It’s a compromise.  Be sure to look at the entire picture when trying to determine whether there is an issue.


195 responses to “Subaru Knock Monitoring and DIT DAM Strategy Changes”

  1. This helped me understand how to interpret part of the datalog for my Stage2+EBCS run in my ’04 WRX sedan. DAM, Feedback Knock and Fine Knock Learning are all within parameters like I hoped and I am achieving rated max boost with it, so I’m happy (16.71 psi @ 3796 rpm).

    • Most of this article applies to yoru 2009 WRX aside from the section titled “DIT DAM Strategy Changes”.


  2. Since there is a mic, could for example; Let’s say not paying attention and shaking the car from almost stalling out, a loose heat shield or even really bad areas of bumpy roads (roadwork / potholes) cause a knock to show? If so, would that show on the fine knock learn, the fine knock feedback, or both? I apologize for my lack of knowledge but my STI is my proverbial baby.

    • Hey Chad, it is possible, however external vibrations/rattles would have to be quite severe in order for the knock sensor to pick them up. I’ve never seen bumpy roads/pot holes trigger a knock event, however it is not uncommon to see a loose heat shield, bracket, etc. be reported as knock. You would most likely see that reported as Feedback Knock initially.


  3. I see you guys say -2.5 of knock correction is normal. What about -2.8? It happens only ever so often and backs up to -1.7, -1.4 etc. A cause for concern?

    • Hey Anthony, it really depends on when you are seeing those corrections. It’s not uncommon at all to see corrections during normal driving (light-moderate throttle). If you are consistently seeing that type of correction while under wide open throttle you may need to address it. Don’t forget, if you are ever unsure about what you are seeing – email a datalog and your vehicle information to [email protected] so we can go over it for you!


  4. I’m getting -1.4 fine knock learning as soon as the car gets into boost, even at partial throttle. It drops back down to 0 right after that. DAM is at 1. Feedback knock is usually at 0 but occasionally goes to -1.4 along with the fine knock learning. 2016 STi Stage 1+ 91 ACN. Is there anything to worry about?

    • Have you tried resetting the ECU to see if the correction returns? It is likely the result of a previous timing event and just has not been learned away quite yet. I would recommend resetting the ECU using your Accessport. If you continue to see those corrections shoot us an email with a datalog and vehicle information so we can let you know if any further action is needed.


  5. This article is fantastic and really puts things in perspective on my 2015. My DAM lowers sometimes but is not accompanied by any knock feedback or fine knock learning. This has put in ease of some of the worrying I was having when my DAM would hover around .8 and would take a good cruise down a freeway before it went back to 1.

  6. hey, I drive a 2009 wrx and would drive my car for about 30 and draw -1.4 knock on the regular and I’m not to worried about that. but I have seen my knock go to -10.50 for no reason. what should I do?

    • Hey Nick! It is quite typical to see some small corrections during a normal drive. With that said, the -10.50 correction is definitely pretty high. Are you seeing that consistently? What modifications are done to the car? If you happen to have that correction captured in a data log send it over along with your vehicle information to [email protected]. We should be able to get a bit more insight on that correction along with some additional data.


  7. I have installed the CVT stage 1 91 octane HWG map and run 93 octane gas exclusively, but I tend to show very constantly Feedback Knock of -1.41 at about 1600-2200 rpm. Also on a few occasions I have shown Fine Knock Learn of -2.11 with my DAM dropping to .875. Every log I have made is clean with no knock. Is this a reason for concern or with in normal parameters?

    • Hey Mike! It is not uncommon to see the knock detection/correction system active on the 2015 WRX. If you can, shoot one of those data logs over to our Customer Service team at [email protected]. We’ll take a look at it and see if there is any cause for concern.


  8. Hey guys I’m new to the accessport I have a 05 sti and the ap is reading that there is a knock… Feedback knock reads -2.00 and ever once in a while go down to -4.00 I also have my dam gauge set it’s only went down to .500 couple times but it normally stays at 1.00 is this in normal range or do I have to be concerned if it help I’m on stage 1 with aftermarket cold air intake and catback

  9. I have a 2015 WRX and my DAM went to .875 the other day and has not returned to 1 after some driving. I am getting Fine Knock of ~ -1.41 and Fine Knock learn of -.35 I have noticed the Fine Knock Learn will blip to -.35 when i give a sudden increase of throttle around 2700-3200 rpm does this call for any concern? The DAM dropped when i was in too high of a gear during some traffic the other day and i saw the Fine Knock shoot up to ~-8 for a second during throttle in too high of a gear.

    • Hey Michael, without seeing a full data log it’s tough to say what may be going on. It sounds like you’ve got a good idea of why DAM dropped. As long as there are not any additional events DAM will eventually learn back to 1.00. I would recommend just keeping an eye on knock corrections as you’re doing to make sure there are not any additional severe corrections. The -1.41 and -.35 corrections are very normal during normal driving. If you have any other concerns or would like for us to evaluate a data log feel free to email [email protected]!


      • Thanks for the response, as you said it looks as though the DAM is learning back to 1, after some more driving the other day it went up to .983 from the .875 as originally reported.

  10. Hi Cobb,

    Just picked up an AP for my 2015 wrx. It is bone stock performance wise and I flashed the Stage 1 93 map onto it. First off let me say the car is an absolute JOY to drive now. The power is consistent now throughout an entire pull which I love. I have been reading about knocking and I feel the more I read the more I get concerned. I have been monitoring the DAM, Feedback Knock, and Knock Correction. DAM has never been anything but a 1. correction has dipped to -1.41 on occasion. Feedback knock runs at 0 typically, I see -1.41 now and again, but yesterday I noticed it recorded an -8.4. The DAM and correction were perfect, however (1 and 0 respectively). Does this raise any red flags in your eyes? I will be doing some 3rd gear data logs later and I will post them later.

    Thanks in advanced.

    • Hi Rory,

      A reading that high was likely some false knock. That’s even more likely if it was during abrupt throttle changes or while shifting hard through the gears. As long as the value quickly returned to 0 it isn’t a red flag. Feel free to send us a datalog to [email protected] and we’ll be happy to help evaluate it!


  11. Hey Guys,
    Is it normal for DAM to START at .685 after flashing stage 0 map on 16wrx? Flashed the other day and DAM started low and worked up to 1 but every time I restart the car the default is .685 and works up from there…. any insight? thanks.

    • Hey David, what you’re seeing is completely normal. In the factory calibration data, the Dynamic Advance Multiplier Reset value is set at .6875. This is the default value after an ECU reset and at each engine start.


  12. Hey everyone,

    Quick question. I am running a 2004 Stage 2 with high flow catted DP and SF Intake with a 91 oct LWG map and still receive some knocking that concerns me. I’ll normally see -1.4 Fine Knock Learning, especially while shifting but sometimes -2.8 while I’m at idle or rolling to a stop. I’ll also see 2.0 Feedback knock going as high as 4 at times. Seems a bit high to me. At this point debating a pro tune but don’t really feel like spending the cash. Thoughts?


    • Hey Dallas! It’s tough to say exactly what’s going on without looking at a data log where those corrections are present. It’s normal to see small corrections during daily driving, you’re mainly looking for consistent or increasing corrections during wide open throttle situations. The 4 counts of Feedback Knock are a bit higher than we typically like to see. Shoot us an email ([email protected]) with some more information about the car (any other modifications, mileage, etc.) and a data log. We’ll be able to go over everything and hopefully point you in the right direction!


  13. Hey guys, I installed my accessport on my 15′ wrx about a month ago. I am running the 93 octane/stage 1 map. Everything was going very smooth until I had Subaru work on the plastic turbo outlet (recalled). Now I am seeing small knock of a consistent -1.41 but that’s not the concerning part. My two main concerns are the a/f ratio is a little on the lean side but not when I am in boost (thankfully), and I have been seeing corrections of +15 and -18. I think those were the most drastic. Could a boost leak cause this? I am wondering if they did not attach the intake piping that leads to the turbo correctly. Just wondering if you had a suggestion. If needed, I can send a data log. Thanks!

    • Hey Jonathan, those corrections are a bit high if you’re seeing them during constant throttle. A data log may indicate signs of a boost leak, but it may be best to look into having a boost leak test performed.


  14. When I got my accessport and cobb air intake for my subaru wrx 2016, I installed cobb air intake and flash stage1+big sf right away with out checking my Fine Knock Learn and feedback knock value, so i’m not sure about those value. and I notice black sooth in my exhause tip (i’m not sure if that’s ok). I didn’t even know what to monitor for.. as I got more into modding my car, I installed COBB Catless J pipe and flashed Stage2+big sf map.. and I haven’t reset the ECU after flashing the map. and I did a little more research on what to monitor on accessport. i’ve been getting 1.41/0 for fine knock learn and feedback knock learn. after a week, and 4 days ago, I was on my way to work-fuel light came on, I stop at gas station to refuel, and I was in hurry, I bought premium 90 octane full tank , and there it was, it messes up my feedback knock values from negative -.70 / +.35 to .70 and up to negative 2.81/0 for fine knock learn. and couple days later did more research and I have monitored the DAM as well. it was like around Dam. Adv. Mutl.. .663 and 1 day after it changed to .750 ( instead of 1DAM). and I did a little bit more research about octane, probably it was the octane I used. I thought I can drive the car until close to empty again but I can’t feel the power and I feel like I’m going to blow the engine seeing those Feedback knock and fine knock learn jumping every time i’m on boost and even sometimes not on boost, after 150 miles I’ve put on since the filled up octane, I can’t bare seeing the FKL and FK values jumping, I decided to get to fuel tank from the back seat and siphon some of the fuel and I thought I have drain all the fuel, I guess there was still about 5 gallon in the tank, after putting the fuel pump back on, White smoke coming out from the exhaust , not a lot but it’s noticeable. Now with 5 gallons of 90 octane, filled up with 92 octane today, reflashed the map, still giving me the .35 feedback knock even at the start up. and worse feedback knock learn values. Now I’m thinking about resetting the ECU? PLEASE HELP. PLEASE HELP. PLEASE HELP.
    *****What to do with whistling every time I slow down and accelerate from first gear and when I rev.?
    *****What octane do you use? we have 92 unleaded premium, 92 plus premium, and 92 super premium. what is better?


    • Hey there! It does sound like the lower quality fuel had an impact on knock, which is why you were seeing the slight increase in corrections. With that said, the corrections you’ve mentioned are still well within what we would deem being safe. If you are not seeing corrections over 3 through either monitor I would not be concerned. I would recommend using the highest grade fuel available as that will ensure the lowest amount of knock.


  15. Hi, I have a 2003 wrx sedan. Current mods are Cobb SF intake, turbo-back exhaust with a high-flow cat, and an up-pipe. I am currently running the Cobb stage 2 map for my car and lately I have been seeing a lot of knock readings. These readings I have been getting are as follows
    Feedback Knock: -2.11 to -4.22
    Fine Knock Learn: -2.11 to -6.68+
    DAM: 11 (continuously)
    These values only exist while I am clutching and gassing from a dead stop, or if I tap the throttle suddenly (aka rev matching to downshift). I also am getting positive fine knock learn readings while I am in boost. (.35-2.76). I only fuel up at reputable gas stations such as Mobil, Exxon, Shell, Sunoco, and use 93 octane. I also have a CEL for a vent solenoid valve function problem but I have had the code for months and only recently started getting all these knock values.. Any thoughts?

    • Hey Dylan,

      If you’re only seeing those corrections during clutch in/out I would imagine the sensor may be simply picking up drivetrain noise. Do you have a factory clutch in the car? Some aftermarket units can be pretty noisy. We may be able to see a bit more with a data log, send one over to [email protected] with your vehicle information and we’ll help to diagnose any potential issues!


  16. Hi,

    I have a 07 WRX TR with the stage two set up with the addition of the sf intake. I was rolling at about 4 miles an hour and in first gear and punched it to merge and received a positive reading on my fine knock learning(0.00/1.58).. I haven’t ever seen a positive value before just curious

    • Hey Ryan, that is normal! Just as they can correct in a negative direction, it is possible to see those values learn in a positive direction as well.


  17. Why would boost leak cause knock? if there’s a leak, less air would go in the cylinder therefore more fuel in the air/fuel mixture. Predetonation occurs mostly when you’re running lean or poor ignition timing. I am feeling heavy knock under WOT which retards the timing heavily but my boost is still strong so there is no leak there.

    Can someone explain what is meant by blow by? I want to understand what that is to diagnose my problem.

    • A leak post-MAF but pre-Turbo would actually be drawing in more air than is measured, thus creating a lean condition. Blow-by occurs when compression escapes around the piston rings and into the crankcase, more typical on higher-mileage vehicles.


  18. Recently my APv3 has been recorded/displaying some interesting numbers. One was the “fine knock learning” display showing increments of .01 (isn’t .35 the norm?). Then, my temperature gauge on my AP showed 206 while the needle on my dash seemed to be at 185.

    Can my APv3 be going bad due to exposure to heat?

    • Hey Jaime,

      You are correct in that increments of .35 are normal for the Fine Knock Learning monitor. Occasionally, there are segments of bad data that get picked up by the Accessport which can be displayed via the Gauges screen or in data logs. An issue with the AP is certainly possible but unlikely. If you see the odd values becoming more frequent please do reach out to our customer service team and we’ll get it taken care of!


  19. So the DAM resets at each engine start-up now, not just ECU resets? I’m running the 91oct LWG map on my ’11 Legacy GT and each time I start the car the DAM comes up at .8. It goes back to 1 fairly quickly if I boost it a bit. Just want to make sure this is normal!

  20. Hi, I get feedback knock when my heater/defroster/ac is on. so every I drive my car with stage 2 plus sf intake, I turn of my heater/ac/defroster.
    How to not get feedback knock? thank you.

    • Hey there, what year/model is your car? Are you seeing the corrections when the condenser is kicking on/off?


  21. Hello,

    I recently installed the Cobb Intake and flashed the Stage 1+ 93 Octane map onto my 09 WRX. I did a little bit of data logging and would just like to confirm that what I’m seeing is alright. In the first data log the DAM stayed at 1 but the Dynamic Advanced Degree went up to 8, feedback knock to -2.8, and 0 fine knock. In the second trip the DAM was still 1 but the Dynamic Advanced Degree also went as high as 8 and feedback knock only to -1.4. Should I be concerned with the Dynamic Advanced Degree? I can’t seem to find much information about this parameter.


  22. Hey guys at Cobb, I have a buddy that has a 2016 WRX and after installing his cobb intake and flashing to stage 1+ big SF 91 oct (using 93 oct in the tank) his DAM keeps dropping constantly to .8XX and then working its way back to 1. But yesterday it dropped to .500 then rebounded to 1 and then today the DAM dropped to .125 then went back to 1! very concerned. fine knock/feedback knock register -4.XX range too and we’re using known good gas…(SIDE NOTE: when he bought the cobb intake brand new directly from cobb we noticed thick oil residue in the intake pipe… not sure if that has to do with anything)

    • Hey Travis! The DIT cars (2015+ WRX) have a much more active knock detection and correction system than previous cars. It’s not uncommon to see corrections however it does seem like there may be something going on if it’s consistently dropping DAM. Have him shoot an email to [email protected] and we’ll take a look. If the corrections are repeatable, have him try to capture them in the data log as it may help us narrow down what’s going on. How long has the intake been installed? We are aware of an issue to a limited supply of 2015+ WRX Big SF Intakes and can replace that unit. Have him reach out to us to get that sorted out.


  23. Hi, just installed my AP into my 2016 WRX and went for the first drive, its amazing! So my AF Sens 1 Ratio is running normal for the most part, 14.7 on idle, 14s when cruising and 22 when I’m off the throttle from a cruise, but i noticed I’m getting around 10s when I’m WOT, lowest i got was 10.14. I’m also currently running the stage 1 ETS intake map. Does my car normally run rich while under WOT? Also i noticed i got a feedback knock of -4.22 but it could be when i was changing gears, and i read above that 2015+ WRX are more active to knock detection, anything to worry about?

    • Hey Jason, most of what you’ve described would be considered normal. The AFR does sound just a touch rich while under throttle, have you verified there aren’t any boost leaks and that the filter is seated properly on the intake tube? We’ve seen issues with some 2015+ intakes where there is not a stop integrated onto the pipe so the filter can be pushed on too far. I cannot remember if the ETS intake has that issue, but it’s worth looking into.


  24. Hi, in response to my post just recently post, couple of updates i noticed in second day of driving. Almost every WOT pull in any gear is hit about 10.14 AFR but i also just found out that the access port is a narrow band sensor so it isn’t the most accurate reading for AFR. but i will also check up on the filter to see if it is properly connected to the intake tube. but i would also like to mention that i get 1.4 on the feedback knock and feedback learning with every WOT run, anything to worry about? i recently read a post on cobbtuning.zendesk saying that it could be a problem if its reoccurring during WOT

    • Hey Jason, the 2015 WRX actually does have a wide band sensor in the J-Pipe which the Accessport is able to monitor. So, what you’re seeing should be pretty accurate. The knock corrections you’ve mentioned are fairly normal to see on the DIT WRX as it has a MUCH more active system than previous years. If you already have a support ticket opened with us, feel free to send a data log to be reviewed.


  25. Hi,

    I just placed an order for Cobb Ap V3 (Through Subispeed), I have few questions.

    Car: 2016 WRX MT/USDM
    Mods: Full Stock


    1. I live in New Jersey and I have unlimited access to a 93 oct fuel (Only using BP gas). I’m only planning to go stage 1 Cobb OTS, which one should I use if i’m planning to use the Map for longterm use with full stock setup? Stage 1 91 oct or 93 oct?

    2. Is it ok to stay with the stage 1 OTS map if I would put an ETS axel back (with muffler) exhaust?

    3. Which important parameter(s) to monitor or to pay attention?

    4. Is it safe to use the OTS map stage 1, permanently?

    Thank you for your help, I’m new to accessports and just giving it a shot since I’ve heard so much good stuffs about it.

    • Hi Mark!
      Congrats on the Accessport! I’ve answered your questions below – please don’t hesitate to reach out if you have any additional questions!

      1. As long as you’re using 93 octane in the car there shouldn’t be any issues with the Stage1 93 OTS map. If you think you may occasionally get stuck with only 91 available and don’t want to have to worry about changing maps when that happens – there will be no harm in just sticking with the Stage1 91 map.

      2. Yes, generally the only exhaust modification that will require a change in tuning would be the J-pipe. An upgraded axle-back or cat-back would not require tuning changes.

      3. Keeping an eye on the following monitors will give a good idea of how the engine is performing: Boost, A/F Learning 1, DAM, Fine Knock Learning, Intake Temperature. A full list of Monitors and their descriptions can be found HERE.

      4. Absolutely. There are thousands of people using the Stage1 OTS long-term map without issue. The bump in power to Stage 1 is still very reliable and within our observed limits of factory components.


  26. I drive a 03 wrx and all I have done to my car is a AP stage 1+ with the SF intake and heat shield and my Fine Knock Learning will be at zero most of the time but when I accelerate at different levels it ranges up to 1.41. How bad is that? My Feedback Knock is at zero but the range values have gone to 2.11/0.00, sometimes it has gone up to 4.22. Could have installing the the SF intake trigger it? Because before I installed the SF intake im almost 100% sure the neither my Fine Knock Learn or my Feedback Knock was always at zero.

    • Completely stock cars will register similar knock values. Nothing you mention here is any cause for concern.


  27. Hi,
    while driving on the freeway this morning, i noticed my feedback knock jump up to 11.5, then it went down to 8, then 4, then back to 0. This seemed very odd to me. DAM never moved off of 1, but 11.5 seems very high on the knock side. Should i be concerned with this? The vehicle is a 08 spec.B.


    • Hi Aaron,

      That’s definitely a high number. Without knowing why it happened, I can’t say for sure whether you should be concerned. However, since it quickly returned to 0, chances are it’s nothing major. I wouldn’t worry as long as it’s not routinely hitting that high of a value.


  28. Morning,

    I’ve recently been monitoring my AF learning 1 (C,D) and have been seeing values up around 6% and have also been experiencing small knock events at low RPM under load after shifting. I just completed a smoke test and didn’t have any leaks. I’m going to continue troubleshooting but had a quick question. Is there any issue with running the ACN91 map on regular 91 octane fuel? My guess is it will provide additional knock resistance but wanted to run it by the experts.


    • Hey Jared! Absolutely nothing wrong with using a map that requires a lower octane than is in the tank. The opposite is, obviously, highly discouraged. With that said, 6% trims aren’t awful and a bit of noise after a shift isn’t all that unusual either.


  29. Good afternoon!

    have a ’16 WRX MT with the 91 map installed (all stock components). I live in Iowa, so map was installed in October and went all through March at a pretty consistent 1.000 DAM. temperatures then were consistenly lower than 40-50 degrees F. Now its May and ambient temps are consistently around 70+ F. I’ve been using the same top tier gas, but now in the warmer temps, my DAM is consistently between .562 and .750. Is this normal? Would you recommend a reflash to the map in warmer weather? use 93 gas over the next few fillups to look for changes? I appreciate the input!

    • Hey Cody! It may be best to take a look at a data log to see if there is any indication as to what is causing the DAM to drop (consistent corrections in specific areas). If you are able to capture the corrections in a log, feel free to email them over to [email protected] and we’ll help you identify any potential issues.


      • Thanks for the quick response Marshall. Are you still suggesting a WOT log, or something more modest in throttle % and/or RPM ranges. I don’t want to risk damaging anything if the lower DAM is indicating a significant problem. Thanks again for your help!!

        • Hey Cody,

          We are generally not terribly concerned with corrections under light/moderate throttle as the motor is under much less stress than at WOT. Most logs we look at will have a bit of noise during normal driving but clean up nicely during a WOT pull. If you can re-create and capture the timing corrections and associated DAM reduction without going WOT, we can certainly still look at that.


  30. This topic always helps me out! I know and understand that Fin Knock and Feed Back Knock are used more as a preliminary to DAM. In the newer 15+ WRX/STI the DAM is what needs to be monitored. I would always be getting a Feed Back Knock of -1.40 or an occasional Fine Knock of -2.45 to -2.80, running on 93OCT SF Map on LWG. I know my DAM did not change and that is what’s best to monitor. It’s nice that the Fine Knock Learn pick’s up every little sound the car makes so if something does go wrong you know or have a good idea where it is coming from. Thanks for all the help Cobb!

  31. I have a ’14 FXT and I’m getting readings at highway cruise speed (under cruise control too) for Feedback Knock and Fine Knock Learning… DAM doesn’t stay 1.0 as much as I would want it… as soon as I give a little throttle FK and FKL goes to zero. If I suddenly WOT it would register a bit more knock before returning back to zero. Is this concerning?

    • Hi Alex,

      Generally, any knock registered at light loads (cruising) is nothing to be concerned of. The DAM may not always stay at 1 on your vehicle due to the strategy mentioned in the last section of this blog post. If FK and FKL quickly go to 0 under load, there is unlikely to be any issue. However, feel free to send us some datalogs to [email protected] and we’ll be happy to take a look!

  32. Hey guys. I own a 2017 sti and I am currently running the stage 1 + 93 oct OTS map. As far as mods, I have the AP of course and I have the COBB SF Intake. Everything else is stock. I noticed recently that I am getting -2.8 for feedback knock and today I did a WOT out of 3rd gear into 4th gear and both feedback knock and fine knock learning were at -1.4. My concern is when I went to get back in my car after a couple of hours. I was driving and only doing partial throttle and the feedback knock went up to -4.2. The fine knock learn was at -1.4. Does this cause for concern?

    • Hey Ryan,

      The values you’ve mentioned are fairly normal for the driving conditions. We typically see some corrections during normal/light driving however are not super concerned about them as the car is not under high loads. Does the -1.4 correction occur consistently in the same range during a WOT pull? If so, give the 91 octane map a shot to see if the less aggressive timing sorts it out. If the correction was a one-time thing it is likely not a cause for concern.


  33. I have a 2017 WRX STI. So I was driving today and it was humid and about 85 outside wind was blowing but warm. I rolled up the windows and had it in Sport Sharp Mode. I did a few 3rd to 4th to 5th gear pulls 4,500 to 5K RPM range I saw I it -7.00 on Feedback Knock. My DAM never charged from 1.00 so I know it wasn’t major. At first I started to panic, I started asking people from Chitown Subaru where I live in IL. I thought bad gas. It turns out I hit that number because I had the A/C while doing the pulls. Maybe you should add this to the forum? With the engine working harder the Feedback Knock would be higher which makes sense. Just thought I would share my 2 cents? Let me know your opinions?

    • Hey Jordan, it is typical for the A/C compressor to disengaged at Wide Open Throttle so it should not cause any issues during a pull. The ECU will actually ignore knock events for a very short period immediately after engaging the A/C compressor. Correction values of -7.00 are pretty significant, if you’re seeing those consistently there may be some cause for concern. What modifications are done to the car and what map file are you using? Feel free to send a data log over to [email protected] if you’d like us to take a look!


      • I can re-create the same issue in my WRX (2013 hatch). When A/C is in engaged (given I am not talking about WOT as I know it is supposed to disengage when you are WOT, however, you could be in a situation where it hit a high knock value and you depress throttle 100% before it gets back to 0), and even more so when cruise control is activated, I get high feedback knock values all the time when it is engaging. I can turn the A/C off and immediately it all goes and way and only comes back when I turn it back on. Those compressors are loud!

  34. It says above that “Fine Knock Learning represents minor learned corrections based on historical Feedback Knock. If the ECU routinely registers knock in a certain RPM and load range, it will apply timing adjustments which can be seen with this parameter.” So how come my Cobb AP is showing -7.03 Fine Knock Learn but Feedback Knock is only -1.41. This is immediately after a reflash.

    • Lenka, those corrections could seen for a number of reasons. The whole correction system is much more active immediately after a reflash, do you see those values persist after a few drive cycles? How does DAM behave?


      • Within 24 hours of reflash DAM started to drop. Day 2, 15 miles or so later, DAM is down to .568. So does Fine Knock Learning not get values from the same sensor as Feedback Knock? I am just trying to understand how exactly it works. Thank you!

        • It is a super complex system with many dependencies that we’ve generalized for understanding during every day driving. It sounds like there could be something going on with your particular car with such high learned values and the dropping DAM. Shoot an email to our support team ([email protected]) with your exact modification list, the map file you are currently using, the fuel type you’re using, and a data log if you have one. With that information we should be able to at least point you in the direction to address the corrections.


  35. Hi there, I have a 2017 WRX and I’m on stage1 93 oct. OTS and I am having a -1.47 FKL at the same time, same value at my FBK under load but it comes back to 0.0 right away, and my DAM does not change it stays at 1.0. BTW I do have a mishimoto cold air intake. is there something to worry about? Thank You..

  36. Hi Kyle! It looks like you’re still responding to comments here, which is cool.

    I’m running a completely stock 07 Outback, and trying to chase down a knock (up to -7 on fine learning knock and 42 degrees ignition timing, medium to hard acceleration). It’s basically constant (on acceleration) if I’m running 87 fuel and the engine is hot.

    I’ve checked for intake leaks (low-tech method, with propane), and come up with nothing.

    I’ve got new O2 sensors (front and rear), but the graphs coming out of them don’t look right – rear O2 oscillates rapidly at idle. Is it feasible that a bad cat is the issue? Or am I looking at the wrong end of the problem? what do I try next? New MAF sensor?

    • Hey Tim! The corrections you’re reporting are almost certainly due to fuel quality. 87 octane fuel does not have the detonation resistance that higher quality fuels do. Even our least aggressive maps, calibrated for use with ACN91 fuel will likely see knock with 87 in the tank. Do you have higher octane fuel available in your area? If so, I would highly recommend moving up to at least a 91 octane fuel.


  37. hey, so i have an 04 forester xt auto, 93oct, gt3076r, 3inch down pipe. perrin inlet and intake, dw300 fuel pump, tgv delete, but stock injectors, and some other things im forgetting off the top of my head. so the car is pro tuned locally, but my DAM has always been at .500 has never changed is that okay? i have a feed back knock sometimes of -2.00 to -4.00 but never under WOT it seems like. but i do sometimes catch cylinder roughness of 1 sometimes but has never gone above 1 and when it does im not in WOT.

    • Hey Josh,

      DAM on an 04 FXT should be able to stay at 1.00 pretty much all the time if your fuel quality is up to par. It can drop at times but it should be able to work it’s way back to 1.00 on its own if everything else is happy. If you haven’t already, I would try performing an ECU reset, that won’t change the tune but it will wipe out all the learned timing adjustments. Then drive the car normally and see if DAM goes back to normal. If not, then it’s definitely not happy about something and making global timing adjustments consistently. There is a long list of potential reasons why DAM may reduce, so I would chat with your ProTuner to see how they want to troubleshoot it. -Adam@COBB

  38. Should I be concerned about getting -1.41 fine knock learn at around 5800-6200 rpm at wide open throttle. I am running the Stage 1 Mishimoto Intake tune on 91 octane.

    • Hi Matt,

      In general, we consider any Knock Correction 2.5 degrees or less to be “normal” and not of major concern.


  39. hi there i have a stage 2 protuned 2011 wrx past tuned on 94 octane gas
    these past few days have been cold -20 Celsius and when in boost my knock feedback is goes to -2.80 for 1 second and when i look back at my AP it says 0
    the knock feedback learning is -1.75 also for like 1 second for example i am doing a small pull 3rd gear form 3k rpm and do a pull till 5k rpm i look at my AP and on the guage on the bottom left it says -2.80 knock feedback but the actual gauge says 0
    is this something to be worried about ?

    • Hi Hamza,

      It sounds like the feedback knock may be attributed to the abrupt throttle change. The fact that it so quickly goes back to 0 fits that narrative. You might try a longer sweep of RPM (like 2500 to redline), and actually log it, and then see if the knock is present at a longer time line. It’s likely not an issue but you may want to take the datalog and send it to your Protuner to get their thoughts.


  40. I’m running your 2016 WRX 93 octane Stage 1+ tune with BigSF intake. In regard to AF ratio what values would you designate as safe for both trim and learning ?

  41. 04 WRX DAM is currently at a 9. With Feedback knock learn all over the place. After reflashing I learned up to the 16 and was great for like a week. Wide open throttle pulls third gear no knock. But then I started getting like feedback knock learn of -6.33 at like the tiniest application of the throttle in low gears. Mechanic can’t find any problems. I’m not sure if they’ve checked for blow by but I’ve cleaned my MAF and they’re saying my engine sounds good. Think it’s just some really bad false knock? Feels like my cars always clinking when I hit a bump and it’s not my suspension as I have new coilovers.

    • Hi Brandon,

      If the car is knocking and DAM is dropping there is likely an issue but it’s tough to say what the issue might be. Make sure the Knock Sensor is tightened down. Beyond that, it sounds like there may be some internal mechanical problems.


  42. Hi,
    I’m pretty new to subie world. I’m currently running my 2017 WRX with the cobb AP and I’m using the stage 1 + mishimoto intake 93 oct map. I also have the nameless muffler deletes. The rest is stock. It’s been pretty good so far. My feedback knock usually is -1.4 / -2.81
    Fine knock learning is -1.4
    DAM is usually 1
    However, after a few months I started seeing that feedback knock can jump to -5.0/-7.0 during high boost. Also the DAM drops to 0.875 but then goes back to 1.
    I’m a little concerned about these readings and I was wondering if you guys could help me with some advice.

    • Hi Eugene,

      Having a feedback knock event that high definitely deserves a closer look. If you’re at wide open throttle and high boost and then seeing those numbers I would not recommend continuing. If it is happening during a hard shift, it may not be as bad. If you send us a datalog to [email protected] with this happening we can help you troubleshoot and help with some advice.


  43. Hi,
    Recently got my 02 WRX protune, 93oct
    DAM was steady at 16 for a while now just dropped to 14.
    Feedback knock is all over the place from -2.50 as high as -10.00! Shop said not to worry about feedback it could be picking up noises from road bumps and such.
    Fineknock is always at 0.00 never changed
    I’m concerned about this DAM at 14 and feedback, any suggestions?
    thanks, franco

    • Hi Franco,

      The shop could be right. It could also indicate a major issue. You should consider when the knock occurred. If it happened during an event they describe, that seems the most likely cause. If it’s just happening under cruise and or at WOT on decent roads and not during hard shifts, and the DAM stays under 16, it probably is more than nothing and you should inspect the car further.


  44. I have a SF intake, Perrin Turbo inlet hose and Nameless catback and a pro-tune in a 2011 WRX with a 257 block. It’s really a toss up as to weather knock is present, some drives are absolutely perfect and everything stays at 0. Almost all WOT events that are flawless. I get up to -2.45 knock event/Fine knock learning on typical steady boost building, although not under WOT. Today as an example I slowly crept onto the freeway and then floored it through third into ~5k in 4th and the DAM dropped to 0.068 with a fine knock learn of constant -4.20 over 3k RPM. Got to work, reset the map and drove around for a bit without hitch, DAM stays at zero and couldnt get a knock event over -.70.

    Could this be a faulty sensor or something?

    • Hi Thomas,

      I’d bet against a faulty sensor. But, it’s hard to say with any certainty what the culprit might be. If I were you, I’d probably take a few logs and share them with my Tuner and go from there to determine whether or not something concerning is present.


  45. Hello i have a 2004 sti and i am getting feedback knock of -2 on full boost (13-15.95 PSI) in WOT. Is this normal?

    • Hi Brandon,

      Thanks for contacting us. That’s hard to answer without having a lot more info. Generally speaking, a couple degrees of timing correction isn’t that big of a deal on a Subaru but it’s still worth checking out. Please send a couple short datalog of 3rd or 4th gear WOT pulls to [email protected] and we will take a look for you.

  46. Hello Cobb team,
    I bought the AP and your Big SF cold air intake and flashed my 2016 WRX MT to stage 1+ 91 octane after I installed the items. I’ve had the items installed for about 3-4 days now from this post and my Feedback knock/Fine Knock Learn are between 0 – -2.11 and occasionally going to -2.8 but they mostly stay and 0. However, my DAM has stayed at 0.750 and never goes back up to 1.00. I understand the the feedback and fine knock learn correlate with the DAM. I also understand that my feedback and fine knock learn numbers are within normal values. My only concern is my DAM reading of 0.750 and not rising to 1.
    I am putting the correct octane of fuel in my WRX as well.
    Any reason why my DAM is not going back to 1??

    • Hi Nathan,

      Thanks for the questions. Where do you live and what are the current weather and altitude conditions where the car is normally driven?


      • @Adam
        I currently live in Southern California. It has been hot here currently around 85-95 F. Altitudes are nearly sea level.

        *on a side note Adam, on a daily drive today my Feedback and fine knock read -4 which then dropped my DAM to 0.500. By the end of my commute it went up to 0.625 and my Knocks are now in normal ranges now, mostly going back to 0. Also I’m currently putting in Costco 91 octane fuel.

        • Nathan,

          Thanks for the detailed response. I assumed that would be the case. The values you are seeing are not ideal of course but also not totally unexpected or concerning in your situation. With the direct injected FA WRX engines. When in California with the lower fuel quality and hot temperatures, seeing DAM drop and/or a few degrees of timing correction is normal. But that isn’t necessarily because the car is knocking like crazy or anything, it is simply a result of the more active timing correction system in those cars, which is common with DI engines in general. It works well to prevent potential knock not only react to knock. I would keep an eye on it to make sure it isn’t getting progressively worse, but I wouldn’t worry about it too much. Just keep in mind that if you are going to track or drag race the car etc, it’s probably a good idea to get some higher octane fuel. But for most driving situations, I don’t foresee any problems purely based on current info. At the end of the day, if you feel like something else may be an issue or the values get worse, feel free to record some short datalogs and send them to [email protected].


  47. Hey, I have a 04 WRX and sometimes my feedback knock is around -3.17 and -6.33. I’m in stage 1 v310 93Oct. and I feel like is kinda high. and I don’t hear any bad engine sounds.

    • Hi Gabriel,

      If it’s during hard shifts or big throttle changes I wouldn’t worry too much about it. If it’s during another situation, feel free to send us a datalog to [email protected] and we can help determine if it deserves a closer look.


  48. So I picked up an AP for my ’08 WRX and applied the Stage 1. I just recently had a Perrin CA Intake installed, and next week I am having a Grimmspeed TMIC and Invidia catted downpipe put on. I have a catback exhaust installed as well.
    I have a ProTune scheduled for later this month but I was wondering if you can provide any advice for what I should be monitoring to ensure I am not doing damage to the car prior to the tune.
    Also – I have not applied the +SF because it is a CA Intake.
    I am more or less driving it like a grandma car, trying to be light on the throttle and keeping the RPM low for now but would still like recommendation on what to monitor and watch until the tune.

    • Hey Peter, driving gingerly is really all you can do. Keep an eye on A/F Learning and A/F Correction while under any load. So long as those trims aren’t maxing our you -should- be okay to drive the car carefully.


  49. I saw my DAM (the small numbers bellow) change. From 16/16 to 12/16.but the big numbers was on 16/16.should I get worried about that?

    And how can I change it from 16/16 to 1.000/1.000
    (is easier to read)

    • Hey Gabriel, was this immediately after a reflash/reset? It is most common to see the DAM system functioning/learning shortly after an ECU Reset which occurs during a map change. If DAM remains at 16 you shouldn’t have anything to worry about.

      The 2002-2005 WRX uses a different monitor type than newer Subarus, it is not possible to convert.


  50. i have a 2013 wrx with an invidia catless downpipe and invidia q300 cat back along with the cobb SF intake therefore i’m running the Stage 2+ w/ 93 octane.
    I cant hear any obvious knowck however on my ~45 minute ride home on the hwy my knock summary on cylinder 2 accumulates to 100+ sometimes.
    The DAM is always at 1.000 (never varies) and the knock feedback spontaneously hits -1.4 to -2.8 despite one ride i remember it being -11.xx
    Should i be concerned? if so, what should my next step be

    • Hi Kyle,

      Good question. That sounds like relatively normal behavior to me. On medium to long distance drives, knock sum will typically increase even if there are no significant knock events. Keep in mind that the threshold for recording a “knock sum” event is lower than feedback, fine knock, or DAM. So it’s common to record a knock sum value that doesn’t even actually produce a timing correction at all. The one thing that I would mention is that if cylinder 2 is increasing at a much higher rate than the other cylinders, then I would recommend investigating that directly to make sure there isn’t something going on with a spark plug etc. It’s normal for knock sum to increase on a longer drive but one cylinder shouldn’t be multiple times higher than the others.


  51. Very good article and very well explained, here I have a doubt, I already have a Costum Map in my car STI 2007 and at low rpm from 2000 to 3000 I have a feedback punch -11.00 in third gear or fourth, sometimes it has given me up to -22.00 in that rpm range, when accelerating thoroughly it goes to -2.5 -1.8, epro the DAM always in 1 and the Feedback Learn always in 0.0, there is some danger in my engine,??

    • Random spikes like that can be tricky. Sometimes it’s just a rattle or similar noise in the engine bay being picked up by the sensor, but you never want to just assume. Naturally, the most important data is what it shows at higher load and rpm, so if it looks good there, I wouldn’t panic. That being said, the best option is to datalog the abnormal values and send the log to your tuner to get feedback right from the person that made the tune.

  52. Hello, my DAM dropped from 1 to .875 and no FKL present. It happened when i was going up hill in third and I had bogged the engine bit. I’ve bogged before and never had the car drop DAM, usually just a bit of FKL. Only thing different is I filled up at a off brand gas station when my usual is Shell. I live in CA so i’m running 91. I want to pin it to a bad tank of gas, but i’m just paranoid. Any input would be great! Also thanks for all you guys for the community!

    • Hi Michael,

      That sounds like pretty reasonable behavior. For now I’d just keep an eye on it to see if you see more timing corrections. If you have suspect fuel quality and lug the engine, it’s going to pull DAM. Typically it will work back to 1.00 as you drive normally. If not, just drive casually until you can get a new tank of gas from a trusted source. Then see if it improves. If it still doesn’t. Then you might want to do some further investigation. You can send us a datalog at that time if needed. Also, it’s always a good idea to double check for any type of air/vacuum leak etc.


  53. I just put in a Cobb electronic boost controller on my 05 wrx, and im getting 14lbs of boost at peak boost. a couple friends have Subarus and they say thats not normal. knock sensor is normal, just wondering why it wouldn’t be pushing as much boost as before I installed the EBCS. Thanks!

  54. My ’07 sti impreza got a reading of -8 knock and it has never been below -2. I am not really sure what I should do or why it is doing this.

    • Hey there, without additional information (data log) it’s hard to say how serious that correction is. Our recommendation would be to keep an eye on how the entire timing feedback system (DAM, Fine Knock Learning, and Feedback Knock Correction) is behaving. Consistent corrections or drops in DAM would be cause for some level of alarm. If you aren’t terribly sure, feel free to email a data log to our Support Team ([email protected]) and we can double-check for you!


  55. Hey Marshall!

    One question really quick. With a 2015 WRX, when I am not boosting, say just cruising around in 5th or 6th gear at 60 or 70 mph, should my boost gauge be reading around -10 to -5 PSI and only really get into boost when I get on the throttle?

  56. Good day,
    I lived in Socal (Palm Springs Area) its been hot lately. So, I was driving my car (today was 105F) and was about to exit the freeway when I noticed my DAM dropped to .562 – first time since I installed a COBB Stage 1 (its been 2 months ago). Still I continued my commute (95 miles approx one way) hoping that it will correct or go back. I am seeing knocks at -4 and -2.8 and im not sure if I read it correctly but I think I saw a “positive” (meaning no ( – ) before the numbers – i think it was 3.4 something. Anyway, i did not noticed any changes in the car behavior. So I continued and went back almost the same miles again (95 miles approx) and my DAM is still at .562 – however when I am cruising – cruise control my knocks has been consistent at 0.00 – with me “driving” i see knocks at lower value but always goes back to zero.
    Did I just messed up my car?
    Thank you

    • Hi Manuel,

      This would be fairly normal behavior for a 2015+ WRX. If you send us a datalog of the issues to [email protected] (along with what car you have) we can help you troubleshoot!


  57. Hi, there !

    Quick question, I have a 2018 sti i currently am running stage 2 91 select with an invida catless downpipe, and a R400 Cat-back exhaust with the stock airbox, my Dam is currently changed to 0 but the fine Knock, and learning is also at 0, im concerned about the dam as it was at 1 when i was on the stage 1 tune
    Thanks, Keith

    • Hi Keith,

      If it stays at 0, there is likely a problem. Exactly what it may be is tough to say with no other information. I’d recommend installing a catted downpipe to help prevent boost control/overboost issues.


  58. Hey I got a 2002 subaru wrx USDM and i got an aftermarket downpipe cobb shortram intake frount mount intercooler and just installed my 3 port boost controller and running stage2+ EBCS 91OCT tune and im running 10psi boost but im also getting Knock Fine Learn -2.37/0.00 and idk what it is and am i getting rod knock and is it bad?

    • Hi Bryan,

      Fine knock learning isn’t indicating actual knock but is pulling timing based on historic events in similar load/rpm ranges. If the car had a knocking rod, it would definitely show up as feedback knock and you’d probably even be able to hear it. As for the underboosting issues, I’d make sure are the vacuum lines are routed correctly and that there are no leaks in the intake tract.


      • what are the most important gauges should i use for my 2002 subaru wrx so i can keep track whats happening with my car?

        • Bryan,

          The monitors above are a good start. There may be some these arguably more important depending on what you’re trying to determine.

          The -2.37 isn’t “good” but it’s not something to be concerned of as the car isn’t actually knocking.


  59. That -2.37 sometimes changes to -1.37 and -0.37 and goes to highly -3.11 those numbers makes me kinda worry so thats

    • Hello Bryan,

      The seriousness of the value is heavily based on context. A value of -3.11 isn’t ideal but also not super uncommon on a DIT car. Recording a datalog to display the overall circumstance related to the timing correction will be more helpful. You can send a log to our support team if needed.


  60. My DAM just recently dropped to 0.188 and stays there consistently as well as fine knock learning showing -3.15 and up to 0.70 and was concerned about this because my DAM has always shown as 1 until this occurrence

  61. Hello,
    I have a question regarding Fine Knock learning behavior I’ve been witnessing. After flashing a new revision of a MAP which as we know resets ECU learning, I will often log a FKL correction in the middle of the first WOT without any previous Feedback knock. It is my understanding that a FKL correction is learned after historical Feedback knock in a particular Load/RPM range. How does the ECU learn a FKL correction without any historical Feedback Knock data to draw from? Am I missing something that would explain these seemingly random FKL events?


    • Hi Jordan,

      That is a good question. The behavior and functionality of the different knock correction systems on Subarus are kinda confusing even though they’re relatively simple in general terms. There are a lot of misconceptions in the community.

      The short answer to your question is that Fine Knock Learning can apply timing corrections at any time, independent of any other corrections. It is both proactive and reactive within itself. Fine Knock Learning can still apply a correction prior to Feedback Knock corrections. Fine Knock Learning can make its own corrections, then applies those to its own memory. So any future corrections made in Fine Knock Learning are products of its own previous corrections…not from previous Feedback Knock. Hopefully that helps, but the short answer is…Fine Knock Learning can make it’s own timing adjustments at any time independent of any other knock systems and learns from itself.


  62. Adam,
    Thanks for the prompt reply!

    That mostly clears it up for me. Good to know you guys are here while I become more familiar with the Subaru logic.


    • Hey Tito,

      Without more information it’s hard to say with certainty. It all depends on consistency of the correction and load during that correction. Generally speaking, under normal driving (not WOT), a correction like that is fairly typical.


  63. Hey I last night as i got home i noticed my DAM dropped to .500 for the first time ive had the car which is about 4-5 months now. On the way home i did do a few WOT pulls but not to redline of course. my feedback knock was -2.8 and so was my fine knock learn as well. Should i be concerned? I have a 2013 wrx hatchback with stage 1 + SF on the LWG 91 octane map with a nameless CBE muffler delete. I’m located here in Northern California if that helps as well.

        • Okay, in that case. As long as there isn’t anything obviously crazy going on or anything clearly damaged etc. then I would drive it casually and see if DAM gradually works back up. If not, I’d record a couple of datalogs and you can send them to [email protected]. Also, keep an eye on things like AFLearning/Correction to see if it has signs of significant fuel trims that would be symptoms of bad sensors or leaks etc.


  64. Hi Cobb Tuning! I have a 2015 STI with an AP V3 with SF intake (running the 91 octane SF+ map). I have never had any issues with DAM doing anything but sit at 1.000 and FKC and FKL sit at 0.000 (maybe the occasional -1.40 FKL). I have owned the vehicle for the majority of its life and installed the AP and intake a year ago.
    This summer I installed a recirculating BOV (Perrin) and had a burble tune (I know its terrible for my Cat…) These add-ons were installed about 6 weeks ago. After these add-ons I didn’t see a change DAM/FKC/FKL except for one day when there was excessive heat (running A/C) and I was driving stop and go (DAM dropped to 0.7xx, FKL dropped to -7.00). The next day I went on a cruise and DAM reset to 1.000 and FKL sat at 0.000.

    The reason for me submitting a comment: I just got back from a 3000 mile road trip with the car down to S. Cal. My DAM dropped to .500 on the way through the Central Valley to Sacramento (100+ degrees). The next day it moved up to 0.562 and has yet to return to 1.000. The same day that the car dropped to 0.500 I was seeing some big numbers in the FKL and FKC (FKL ranged from -7.00 to 3.xx). These changes in numbers never occurred during any big accelerations. I have not seen anything happen to the FKC since leaving California but still observed some numbers in the FKL range from -4.00 to 0.00)
    In Oregon I use 92 octane with the 91 octane map. So I was using a lower octane rating than the car typically uses, also I went to plenty of gas stations (I try to be consistent). I am hoping that maybe my second full tank of gas from my regular station helps resolve, but I wanted to see what ya’ll think as well. Sorry for the long message, and thanks in advance for any incite!

    • Hi Josef,

      Definitely sounds like something that you need to keep an eye on. Ultimately in order to diagnose that kind of behavior, a couple of datalogs are needed to see more context for the overall symptoms. Typically we would be happy to review some logs to offer additional feedback but you’ll need to be on an OTS map. If you are using a modified map then you will need to communicate with the person that made that tune in order to receive support for engine behavior on that tune.


  65. Hi Adam, Marshall, Kyle!

    I hate to tack another post onto this article, but I’m a little curious about the behavior of my 2013 WRX. I’m running your Stage 1+ ACN91 SF map (with the SF intake) and high wastegate, as I was receiving about 1.5lbs less boost than expected with the normal WG map. I’m currently hitting around 16-16.5lbs of boost without issue, but do notice a fine knock learn of -1.4 very consistently under WOT while in boost, particularly around 3500 RPM. DAM is always a 1. A/F ratios float around 11.14.
    This only happens while in boost, if I’m in vacuum it doesn’t happen at all. Would this be considered normal? I do my best to only visit quality gas stations like Chevron, Shell, etc.


    Alain H.

    • Hi Alain,

      That little amount of correction with the FKL parameter would not be concerning. If you’re ever worried, feel free to send a datalog to [email protected] and we can take a look and see if there are any potential issues.

  66. Hi Adam, Marshall, Kyle!

    Recently, I saw changes on my Dam level from .875~1 to .75~.812. I went ahead and did a datalog at 3rd gear( from 35mph to nearly redline) it showed 0 feedback knock and but fine knock from (0.35 -> -3.16 -> .7). I have 2017 wrx with stage 2 protune on 91 gas. What should I test first or how can I address this issue?

    • Hey Luan, since you’ve had the car custom tuned by a Protuner we’d have to refer you to them to provide feedback specific to the tune. With that said, that amount of FKL isn’t terribly worrying and within reason on the DIT WRX. If you’re confident in the mechanical condition of the car (spark plugs, quality fuel, etc.), I’d recommend reaching out to your Protuner with that datalog to make sure everything is as they would expect.


  67. Hi, so I live in Alaska where we have 90 Octane and I’ve been running the OTS Stage 1 map on my 2010 STi. I’ve ran the OTS Map for almost a year now with no issues till recently. The engine has lately been reading and adjusting for knock with pretty high numbers as the temperature is dropping outside. I’ve been getting readings as high as 7 for Fine Knock Learn, and -4 for Feedback knock. The DAM is still at 1. Should I be concerned? I recently just unmarried the accessport as I am not sure if engine damage is occurring.

    • Hello,

      Thanks for contacting us. The first step is to record some datalogs to get additional information and context to see what is happening at the moment of timing correction. Naturally if it happened suddenly then the tune hasn’t changed so the issue is either fuel related or mechanical. A datalog will help point out other abnormalities. Feel free to email a copy of the log file to [email protected] if needed.


  68. i know you guys are tired of hearing about this but i have had the AP for about 3 months now. i am running the stage 1 map 93 octane on my 2017 WRX. I have never really had any issues. it would knock here and there but nothing really too drastic. Today on the way home form work the DAM dropped to .500 and pretty much stayed there the whole time. i drive about 90 miles a day for work. I have read a couple of these before so i tried at full throttle full boost and its not knocking there, but it is knocking at about the 2.5 rpm- 3 rpm and i am going about 70mph. Every-time i would touch the gas peddle it would knock .35. the range that i had on feedback knock was -2.81 to 0 and on fine feedback learn was -2.81 to 1.05

    Is this something i need to be concerned about, because i am about to buy the cold air intake and if my car is messing up i would like to get that taken care of first. Thank you for your time have a great day.

    • Hi Kourtland,

      The knock readings are less than ideal but not really indicative of a significant issue themselves. It could be as simple as less than stellar fuel. As for DAM drop, it is fairly active on the 15+ WRX. Has it risen back to 1 since you’ve written this? If not, you may send in a datalog for a closer look. In that case, please send it to [email protected] and we can help! If it has returned to 1, I’d chalk it up to the car doing what it is intended to do.


  69. Hey guys, I have an 05 sti with a built motor and an AP v3. I have reset my map somewhat recently, and usually right after I reset my DAM is at 1.000, however it has recently dipped to .875. I have owned the car for 2 months and always seen some FBK on light throttle, rarely ever under WOT. The most common time for the DAM to drop is in a snowstorm or super cold weather, which confuses me. Also AF learning is at -14% on idle, but the car hits full boost so i have a haard time imagining a boost leak. Any thoughts?

    • Hi Noah,

      With a built motor and custom tune, it’s difficult to troubleshoot that kind of issue without direct access to the car. I would recommend recording some datalogs on the Accessport and sending them to your tuner. He will be much more familiar with the engine and his calibration to offer proper feedback.

  70. Why would my Dynamic Advance be -5.00 when I hit the throttle at first start, cycle the ignition and immediately returns to the positive value?

    • I should probably add to the comment that I have a 2003 WRX 5MT, TD0520G, 850cc Injectors, 320AEM fuel pump, SPT Intake, with 9.0 to 1 compression. STi intercooler. Cobb port ECBS.

    • Hi Jason,

      It’s tough to say on a custom tune. There are a lot of settings that can be manipulated and without any insight into them, my guess would be as good as yours. I’d recommend getting with your tuner on any concerns and they should be able to help!


  71. Hey guys, i have a 2006 Legacy GT, only mods are a cat-back exhaust, and a silicone turbo inlet. Im running the Stage 1 93 oct v3.50 tune. Under WOT im seeing -8 and sometimes -10 Feedback Knock at 4200 RPM or higher. I Have the data log for the -8. When it spiked-10 it also brought my dam from 1 to 0.00. no log on that event unfortunately.

    • Hi Jordon,

      If this happens every time you go WOT there is likely an issue. If it was the one time, it was likely noise as described above. If you send the log to [email protected] we can take a look!


  72. hey i have noticed that I am getting some knock when i am driving around and when i am on the highway.
    i have a 2013 wrx limited

    Tonight my:
    – knock feed back was -8.40 then reset to 0
    – fine knock was -1.40 and then it reset to 0
    – DAM stayed at 1.00 and doesn’t move when I get knock knock feedback

    I use 91 gas from shell
    i have a cobb intake and I am running the Stage 1+ HWG map

    would this be a reason for concern ?

    • Hi Keshan,

      Since the knock monitors returned to 0, and DAM stayed at 1, everything is likely fine. If you continue to see major knock events, send us a datalog to [email protected] and we can take a closer look.


  73. 04 fxt added new and used stuff for the VF39 map, ACN 91 and now the DAM wont budge off .50 and FKL readings stays a solid 0.00. 125 miles and nothing changes…..thoughts please

    • Hi Vin,

      I’m sorry to hear about the issues. It’s tough to say what the problem may be. If you send a datalog to [email protected] we may be able to help point you in the right direction.


  74. I have a 2015 MT WRX currently running stage 2 BigSF MAP. I installed the BigSF CAI about 1 month ago and on the stage 1 Big SF MAP and did a few pulls and noticed slight FNL without FK and DAM at 1. Max boost was 17ish (I live in SLC, UT altitude is about 4600 ft). I didn’t think much of it until after installing the Cobb resondated jpipe and mid pipe. I kept the OEM exhaust (for now). Once switching to the current MAP noted above I immediately began noticing FKL -0.35- -4.22. I have been noticing over boost up to about 18.5 psi at WOT. I have reset the ECU and tried both HWG and normal WG with no change that I am aware of. I am now regularly seeing FKL even when not in boost. I wondered if this might be from something with installation so I rechecked the the car over and did not come across anything alarming. I made sure that the restrictor pill was also removed. I have not had any CELs occur, but am going insane. One thought that arose to me is that this may be from the gas? I have been driving slow staying out of boost and watching Buick’s pass me:( I have sent a few data logs to Andrew and our plan is to run the gas and then get new stuff. I wanted to just reach out and see if there are any other suggestion. I have no other mods on the car. It is only at 42K and has been amazing up until the bolt on mods.

    • Hi Tony,

      You’re in good hands with Andrew. My guess based on the same info would also point to gas. He’ll be able to get into more detail with a new tank and datalogs.


  75. Hey Adam and Kyle,

    I have an 09 WRX with the stage two kit on it. Running the Stage 2+ SF OTS map. When monitoring my feedback knock I always seem to get a lot of knock detected. When I am around .8-.9 g/rev load and approximately 2800 RPM. That amount of load at any other RPM I’m good, or that RPM at any other amount of load I’m good. Just at those very specific points my feedback knock will go crazy retarding all the way to -11.5 deg. I have tried fattening up the mixture in that spot as well as retarding timing using my accesstuner software. But both methods did not help my phantom knock. I know that is right on the limit for when the knock detection gets enabled or disabled… but have you ever seen anything like this before? What can I do to eliminate this because in a worst case if I hit that spot a couple times it will actually reduce my DAM.
    Thanks for the Help!

    • Hi Dalton,

      It’s not something I’ve seen specifically before. It’s tough to suggest a fix without knowing what is causing the knock to register. If it were me, I’d probably take it to a shop to help diagnose the issue. If you have all of the correct modifications for the map you’re running, it shouldn’t require any tuning changes.


  76. Hey, I drive a 2003 WRX Wagon and I’ve been getting Fine Knock Learn readings at -8.09 at low rpms fairly consistently and Feedback Knock occasionally reading -2.33 and a couple times it has read -6.33. The DAM reading has never dropped below 16. When I do a pull with WOT, in the higher rpms from around 3,000-5,000, I experience some fuel cuts or bogging and get Fine Knock Learn readings of -1.05 to -1.76 every time it cuts. Are the fuel cuts and knock readings correlated? Or Should I be worried about anything?

    • Hi Coleman,

      It’s tough to give anything concrete with only that information. You definitely want to determine why the fuel cuts are occurring and get that addressed. Once that is taken care of, and if then the knocking persists, we can dig deeper. It’s also helpful to know what modifications are on the car and what map you are running.


      • I’m still not 100% sure if it is fuel cuts because I’m still hitting target boost and when it bogs down for a second the AFR is still on the richer side and it doesn’t lean out but it certainly feels like it. I am running the Stage 1 91 map with an spt intake, Turbo Heatshield, cat back exhaust, and before I got the accessport I had a CEL for a nonworking Catalytic Converter on my stock downpipe because its starting to go out.

        • The intake and/or the cat may be causing issues. It may also be a failing fuel pump or injectors. I’d recommend taking the car to a tuning shop that does Subarus. With the age of the bugeyes, it’s really tough to narrow down problems via the internet.


  77. Hey Cobb Team,

    I have a 2006 Forester XT, with a 3″ TBE. I’m running the stage 2 OTS tune. My DAM never seems to change off of .625 (default after an ECU reset). FKLC is always 0, so it doesn’t seem to be trying to learn the DAM up. my FBK is always less than 2, and occurs in the area typical for knock, cruising low load (highway) quick throttle changes, hard shifting. I spoke with a couple local tuners and they were unsure of what might be causing this.


    • Hi Ian,

      Please record a few short datalogs at cruise as well as a short pull and email them to [email protected] along with any info about the car and the behavior you can list.


        • Hey Ian, sorry we didn’t get back to you on that quicker. When logging for general troubleshooting, we simply suggest the Default Log List. This can be done by scrolling up while on the Gauges screen, selecting Setup, then select Configure Datalogging, and finally select “Reset to Defaults”.


  78. I installed the stage 1+ was fine for a day, now the DAM is reading 0.68 from 1.00 and wont return to 1.00 and the fine knock is at 2.68 it was at -2.6 … should I be concerned at all?

  79. Hey! I recently got an access port for my 2017 wrx and my DAM readings are worrying me. When I first got the access port it read 1.000. Shortly after it went down to 0.500 and stayed there for a couple weeks. Last night it went down to 0.375 and has still not returned to 1.000.

    • Hi Nicholas,

      If you take a datalog and send it to [email protected] we can help you troubleshoot. Be sure to include which map you’re running (including fuel) along with the modifications you have installed.


  80. hi, I have 2002 wrx with cobb air filter and cat back exhaust. This morning when I stared my car the DAM was 12 and when I started driving it went to 16.

  81. Hello, today I noticed when driving my 2021 wrx with a pro tune, 1.41 fine knock learning kept popping up when I was under light throttle and then would go back to zero when I let off. My DAM didn’t drop from 1.00 and the feedback knock correction showed no knock events during this drive. It probably showed up at least 7 times during light throttle and when revving the engine when stopped.

    • Hello,

      That doesn’t sound like any cause for concern. If you are worried, I’d recommend sending your Protuner datalogs to see what they might say.


  82. Everyone has been talking about DAM drops to .875 or .750 and here is mine living in the range of .150 to .500 at the most. I only have a cat-back exhaust, stock everything else, changed the plugs, had a smoke test done and do regular maintenance. I had a stage 1 map, but removed it to stage 0 with the dam drops. Ive had Cobb review a 3rd gear pull and they said everything was fine, but there has to be something wrong right? My WRX hates running the A/C and being under load at low speed, and i have a hard time believing thats how these cars are supposed to be. Is there anything else i can check/do? And yes ive checked for loose heat shields and or brackets.

    • Hi Sam,

      If you’re not getting gas from a top tier station, try that. Otherwise, it’s tough to point you in any direction without physically being with the car.


  83. Hey there, I have gone through all these comments looking for someone who has been having the same issue as me or simialr and havent seen anyone with the exact issue.

    I have a 2017 WRX MT with about 84,000 Miles. I recently installed the V3 accessport, I know better late then never right? I will say “WOW” it drives freaking amazing and honestly never knew what I was Missing until I installed the AP.

    The Issue I am having is that on the first day after installing the AP I uploaded the Stage 1 93 Octane map and my DAM was reading 1. On the next day, after starting my M/V, I began driving and noticed the DAM was reading 0.75 and after 3/4 days has never returned back to 1.

    I am completely stock, only things is CNT Racing muffler deletes as well as the Grimspeed Air Filter replacement, until I am able to install the SF Intake and can Flash “Stage 1+ 93 Oct SF Intake OTS.”

    My AF ratio is at 14.7
    Boost: is at the same ranges.
    Feed Back Knock: has read -1.05 to -3.11
    FKL: have seen -1.2 to -1.7 or so roughly
    DAM: stays exactly at .75 and has never gone up or down sense the second day driving.

    I am just curious and wondering if I should reflash the Map and if this is something to be concerned/worried about. I know that the DAM with the DIT may have a little wiggle room but everyone says that the DAM should be staying at 1

    I also have noticed if I am in 5th gear anything after about 3K RPM’s or 3500 RPMs if I hit about -4 PSI or higher moving positive the Feedback knock will be at -1.10 and as soon as I decrease RPM’s goes right back to 0.0.

    I dont even believe I have done a WOT yet. with this OTS Map.

    • Hello,

      Nothing you describe sounds concerning. I would recommend using the stock filter element though.


  84. So I recently bought a 2017wrx that has a turboback exhaust with a catted J pipe. It’s running a stage 2 91oct v361 tune and is giving me some issues. The car will randomly read up to -4.22 knock and won’t budge from .750 DAM I thought it was normal then found out it wasn’t so I put octane booster in it and am going to fill up with 93 once the tank is up. The fine knock learn gets up to -9 and I honestly don’t know what to do since COBB got rid of this tune as far as I can see so I don’t know if the tune calls for an intake as well. So my questions are would an intake even help? Would I need a custom tune? Is this even fixable or have I already damaged my engine.

    • HI Cameron,

      I’m sorry to hear you’re having issues. It’s tough to say what issues (or even if) might be happening. I’d recommend getting to a shop to help diagnose the issues if you want to keep it as is. If it’s just the Stage 2 map, it uses the stock intake. ANY other intake will cause issues. So, I’d recommend returning that to stock ASAP. I’d also recommend returning everything to stock and using the stock map temporarily while you figure out if there are any issues present. If things are good there, you can then continue to add maps and their corresponding parts.


  85. Hello there, i am currently running stage 1+ on 2016 STi, here recently WOT in 2-4 gear I’m getting a reading -.4, but when I’m on the highway in 5th gear doesn’t show anything, Dam’s is 1 and the feedback is 0, it is just the feedback learn. Also since it is colder weather, could that have anything to do with it. it has been in the 20’s

    • Hi there! There are a number of things that could lead to small corrections like that and it’s possible the cooler weather is contributing. If you aren’t seeing additional corrections on top of that learned value, it will likely slowly work it’s way out over time/mileage.


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