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.

Rene to my rescue

Although the replies to my post in romraider explained what went wrong, no one really gave me the full details on how to resolve it. Luckily, Rene was able to help me out. Here's his reply:

"Your timing seems very high in the mid range. I believe a good target is 10-13º in the 3000 - 4000 range. i believe you said you were running a VF 34 right? I have a VF 39 on my car now and I will try to mimic my timing table on your map but I know the resolution of the maps are different, mine to yours (16 vs 32 bit). I will try to find you a base map but I need a full mod list, sorry if you have sent me the list before.

As for your corrections I believe Subaru specs are +/- 10 % a good tune will be +/- 4-5% so if your corrections stay in that range there is no problem."

After sending him my map, he modified the following tables:
Timing:
- Base Timing
- Timing Advance (Maximum)

Fuel:
- Primary Open Loop Fueling A
- Primary Open Loop Fueling B

After that, when I did logging for my 3rd Gear WOT from 1 to 1.5 bar, there's hardly any knock correction!

Here's my learning view
Before several 3rd Gear WOT (a week+ of normal driving since my last flash):


After several 3rd Gear WOT:


My 10-50g/s are slightly higher (between 3-4%) but I think it is still acceptable.

P0244 CEL Reasons

Ok, I didn't really get around to flashing the changes to my ecu rom as mentioned in my previous post. The main reason is that the P0244 CEL is an indication of me not doing things right.

Firstly, my boost limits are set at 1.4 bar and I am boosting at 1.7 bar, that's why I am getting P0244. See screenshot below:


But setting the boost limits higher is not right because I'm running my OL MAF Scaling with my methanol injection. This is not right:

1. my MAF Scaling is not accurate (methanol skews the MAF scaling)
2. MAF scaling should be done on fuel pump only so that in the event of my methanol failing, I know that my engine still runs fine.
3. Also, I should not be boosting at such a high boost when MAF scaling when my car has not been tuned for it. 1.7 bar is pretty high and in the logs, my Feedback Knock Correction* (degrees) when to -4.22 degree.

Actually 1.7 bar is pretty high.. my engine could blow if my parameters are set correctly. :-(

For those who wants to see what others had to say about what I have been doing, here's the thread on romraider: topic3279.html


I've emailed Rene and he's been helping me abit. I'll update it on my next blog post.