Welcome to the North American Subaru Impreza Owners Club Thursday April 24, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Engine Management & Tuning > AccessPort

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 01-31-2013, 11:57 PM   #1
Nimbus09
Scooby Specialist
 
Member#: 212399
Join Date: May 2009
Chapter/Region: NWIC
Location: portland, or
Vehicle:
09 wrx 301hp/328tq
'00 miata blue

Default How much knock is too much?

Hola guys (Bill),
I read the other thread titled similar to this and didn't really take much away from it.

The question is simple, how much knock at WOT is too much? Is any acceptable?

My experience is, when I first reflash to a map, I don't see any knock the first few runs. Then, a month later, I do a log and see some knock at roughly peak torque and occassionally some around 5500 rpm. Why would this be time dependent? Is it ok to see -1.4 degrees pulled every now and then at peak torque (3500) or higher (5500) at WOT?

Thanks!
* Registered users of the site do not see these ads.
Nimbus09 is offline   Reply With Quote
Old 02-01-2013, 08:36 AM   #2
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
Default

Quote:
Originally Posted by Nimbus09 View Post
Hola guys (Bill),
I read the other thread titled similar to this and didn't really take much away from it.

The question is simple, how much knock at WOT is too much? Is any acceptable?

My experience is, when I first reflash to a map, I don't see any knock the first few runs. Then, a month later, I do a log and see some knock at roughly peak torque and occassionally some around 5500 rpm. Why would this be time dependent? Is it ok to see -1.4 degrees pulled every now and then at peak torque (3500) or higher (5500) at WOT?

Thanks!
When the knock is occurring is the key factor here. If you see feedback knock correction when mashing the throttle or abruptly lifting off the throttle, then this is normal noise. If you see consistent feedback knock correction during your WOT run that is not due to the above, then that is something you would want to address. One typical solution would be to move to a less aggressive map (ex. move from 93 to 91 octane map while still running 93 octane fuel). You would also want to make sure you are using gas from a decent gas brand. There can be other reasons for consistent WOT knock, including mechanical problems.

Fine knock learning is a lot more tricky to analyze. This is because it is learned based on an event and then re-applied again and again to a sometimes broad load and RPM range after that event. It will be re-applied and then gradually ramp back down to zero. So, you really don't know under what conditions the fine knock learning was learned. Sometimes, with WOT fine knock learning, it can get learned when abruptly lifting off the throttle at the end of your WOT run. Then it gets re-applied and you see it during the WOT run which can be confusing. Generally, though, that is a single count (-1.4) correction. If your ECU supports the knock sums parameter(s), you can log it/these to give you a better idea of when fine knock learning is actually learned. The knock sum value(s) will increment when there's perceived knock. Do not be concerned with the values themselves - you will see sometimes larger numbers. This does not mean you are knocking quite a bit as these numbers are meaningless (they increment even at idle when the knock detection system sucks as determining any actual knock). Cylinder 4 knock sum (if your ECU supports per cylinder knock sum) will also generally be higher than the others - this is normal. You just want to look at when the knock sum increments at WOT - this is indication of knock. You will see it when feedback knock correction drops (from previous value) and when fine knock learning is learned. If knock sum does not increment when you see fine knock learning, it means that it was learned previously and you are only seeing what is being re-applied.

The final thing to check is the dynamic advance multiplier (DAM). For the 2.5L Subarus, this will learn up to 1.0 and should stay there. It should not drop from 1.0 as this would indicate knock. However, keep in mind, depending on the map, the DAM may start out at an initial lower value after the Accessport install, map reflash, ECU reset or disconnecting the car's battery. This is normal behavior in that case and does not indicate knock.

Bill
Cobb Tuning is offline   Reply With Quote
Old 02-01-2013, 09:41 AM   #3
Nimbus09
Scooby Specialist
 
Member#: 212399
Join Date: May 2009
Chapter/Region: NWIC
Location: portland, or
Vehicle:
09 wrx 301hp/328tq
'00 miata blue

Default

Interesting, thanks for the response.

Guess, follow up question is: does that mean the best condition to determine if a map is good is to log immediately after reflash so the car doesn't have time to register false fklc (given your DAM is at 1)?

It just bugs the heck out of me when I first put a map on and it looks great, only to see the car show knock a month down the road with the very same map.

Also, why doesn't Cobb recommend just logging knock sum if that's the best parameter to show true knock?
Nimbus09 is offline   Reply With Quote
Old 02-01-2013, 10:20 AM   #4
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
Default

Quote:
Originally Posted by Nimbus09 View Post
Interesting, thanks for the response.

Guess, follow up question is: does that mean the best condition to determine if a map is good is to log immediately after reflash so the car doesn't have time to register false fklc (given your DAM is at 1)?

It just bugs the heck out of me when I first put a map on and it looks great, only to see the car show knock a month down the road with the very same map.

Also, why doesn't Cobb recommend just logging knock sum if that's the best parameter to show true knock?
The reason that fine knock learning doesn't show up immediately after a reflash or ECU reset is because the ECU will enter a mode that looks at making changing to the DAM after that reset rather than fine knock learning. In that case, either the DAM would drop or feedback knock correction would drop if there was knock (dependent on conditions). Feedback knock correction is the default correction so it can be used (depending on conditions) regardless if the ECU is poised to make changes to the DAM or changes to fine knock learning (as conditions dictate - those changes would be disabled and feedback knock correction would respond to knock). After a period of time, the ECU determines that the DAM evaluation is done and moves to making changes with fine knock learning (with feedback knock correction still as the default).

Regardless, if you get a WOT log shortly after a reset and there's no feedback knock correction and the DAM doesn't drop, then there's was no perceived knock.

We don't add knock sum to the default set of parameters as only the later ECUs have it. We want a default set of monitors that is as consistent as possible across all the Subarus we support. But, you certainly add it to logging set if you have a particular need to do so. In this case, it would be to determine when fine knock learning is occurring.

Bill
Cobb Tuning is offline   Reply With Quote
Old 02-01-2013, 02:01 PM   #5
Nimbus09
Scooby Specialist
 
Member#: 212399
Join Date: May 2009
Chapter/Region: NWIC
Location: portland, or
Vehicle:
09 wrx 301hp/328tq
'00 miata blue

Default

good info, thanks!
Nimbus09 is offline   Reply With Quote
Old 02-03-2013, 11:09 PM   #6
Nimbus09
Scooby Specialist
 
Member#: 212399
Join Date: May 2009
Chapter/Region: NWIC
Location: portland, or
Vehicle:
09 wrx 301hp/328tq
'00 miata blue

Default

Quote:
Originally Posted by Cobb Tuning View Post
The reason that fine knock learning doesn't show up immediately after a reflash or ECU reset is because the ECU will enter a mode that looks at making changing to the DAM after that reset rather than fine knock learning. In that case, either the DAM would drop or feedback knock correction would drop if there was knock (dependent on conditions). Feedback knock correction is the default correction so it can be used (depending on conditions) regardless if the ECU is poised to make changes to the DAM or changes to fine knock learning (as conditions dictate - those changes would be disabled and feedback knock correction would respond to knock). After a period of time, the ECU determines that the DAM evaluation is done and moves to making changes with fine knock learning (with feedback knock correction still as the default).

Regardless, if you get a WOT log shortly after a reset and there's no feedback knock correction and the DAM doesn't drop, then there's was no perceived knock.

We don't add knock sum to the default set of parameters as only the later ECUs have it. We want a default set of monitors that is as consistent as possible across all the Subarus we support. But, you certainly add it to logging set if you have a particular need to do so. In this case, it would be to determine when fine knock learning is occurring.

Bill

i just re-read this. my question is really not why knock learning is not registering after a reset. i understand that it wouldnt

my question is, after i initially reflash, my logs are DAM=1 and FKLC=0 all around the rpm range. a month later, DAM=1 but FKLC is not 0 anymore and i actually see some feedback knock too. i don't understand what happens in that month that the very same map gives me crappy results later.
Nimbus09 is offline   Reply With Quote
Old 02-04-2013, 08:37 AM   #7
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
Default

Quote:
Originally Posted by Nimbus09 View Post
i just re-read this. my question is really not why knock learning is not registering after a reset. i understand that it wouldnt

my question is, after i initially reflash, my logs are DAM=1 and FKLC=0 all around the rpm range. a month later, DAM=1 but FKLC is not 0 anymore and i actually see some feedback knock too. i don't understand what happens in that month that the very same map gives me crappy results later.
A reflash does the same thing as an ECU reset - that explains why fine knock learning is not being used right after a reset. The amount of time it spends in the DAM learning mode (before switching to fine knock learning mode) depends a lot on driving conditions. Certain conditions (steady load/moderate boost) will speed that process while others may prolong it. But, it shouldn't take very long on these cars.

Really, what you are seeing for knock correction depends on where you are seeing it. Some amount of low load correction or correction with throttle changes is normal noise and not something to be concerned about. If you getting consistent correction during your WOT run (other than due to mashing the throttle or lifting off it abruptly), then that would be a concern. As to why you may see more correction well after a reset/reflash (if the DAM starts at 1.0 initial), it may just be a coincidence (knock is not always consistent run to run) or it could be something fueling related if your long-term fuel trims are learning something that is not appropriate. For example, the A/F Learning 1 "D" range is also applied in open loop, so if you see if pulling fuel (with a notable correction), that will also impact your WOT fuel targets and there could be some relationship there with the knock. But, those fuel trims are cleared after reflash/reset so they would start at 0.

Bill
Cobb Tuning is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 11:04 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.