IAM = 8

From merchgod's post on romraider:

Timing Basics
Ignition Timing is determined by the ECU as follows:

Total Timing = Base Timing + Knock Correction Advance + Other timing compensations

Other timing compensations = other compensations including those for IAT, ECT, per cylinder, among others.

Knock Correction Advance = (Timing Advance Maximum * (IAM/16)) + feedback knock correction + fine learning knock correction

Note: The IAM (ignition advance multiplier) used in the formula above is the raw value (ranging from 0-16) for the 16-bit ECU. For the 32-bit ECU, the IAM will range from 0 to 1 (substitute "IAM" for "IAM/16").

From the formula above, you can see that Knock Correction Advance (KC) consists of three elements. How these values are determined and how they interact with one another will be discussed below.

Although exactly how the ECU determines knock (based on input from the knock sensor) is not fully understood, the result is quite simple. The knock signal is either set or clear. That it, as far as the ECU is concerned, there either is knock or there isn't. There's no level of severity that is stored or used for knock control.


Rough correction involves manipulating the IAM (ignition advance multiplier) due to knock. This has the result of correcting timing advance across the board (timing advance maximum * IAM/16). The IAM can range between 0-16 for the 16-bit ECU.

In my case, if you see the Learning View of my earlier post, my IAM is consistently = 8, which means that I am always in rough correction mode which is bad as indirectly, it means that I am experiencing knock.

If you want read more about how the Subaru ecu handles knock, read this post: topic1840.

Well, why is it Learning View is not showing knock? ravenhil from subaruclubsg suggested I log only knock parameters to improve the resolution and true enough, I am getting knock:



This means that I have too much timing. I've search on romraider and found that mickeyd2005 has written a spreadsheet that helps to tune timing. See here: topic2546

I'm going to try that one out and see how it works out.