Thursday, November 18, 2004

Subaru ECU Learning

I've researching how the Subaru ECU in my WRX reacts to operating conditions to help me interpret the logs I've been getting from my Delta Dash. I found this thread "knock sensor activity in Deltadash?" at NASIOC which has some good information in it posted by Shiv from Vishnu Performance. I'll quote what I found important here:

The code at our disposal allows us to change the rate of retard, rate of advance, operational load range, operational rpm range, learning authority range, etc...

(The ECU) will pull back timing and store the knock correction levels in memory. If it does this in enough places in the table, the advance multiplier will drop and stay dropped until its sees consistent maxed-out positive knock correction.

The knock control system is active from ~2000rpm to ~6000RPM, give or take a few 100rpm based upon application/mapping. It's also active above moderate load (under boost). It is very unusual to hear audible ping within those conditions with deltadash consistently showing no drop-outs in knock correction.

BTW, if you try filling up a stock car with 87 octane, it will ping instantly, pull back timing, send the ignition advance multiplier well below 4 which will make the car run on its rich fuel map. For the most part, it will run ping-free. But every now and then, it will try to advance back to normal. And in doing so, it may ping audibly.

FWIW, I never look at the knock signal display. I only concentrate on knock correction as it's never let me down. Not only does it tell me when the car is starting to detonate, its behavior also gives insight to how severe or minor it is.

Recently I switched from the Cobb Stage 1 map back to the stock map. After a reset and a drive to work, the IAM advanced itself to 16. However, after driving a week, it's now down to 12 indicating that the ECU has detected enough knock that it decided to lower the maximum amount of timing it is willing to run. The trick now is to try and figure out why my engine is encountering detonation. Is it the poor quality gas we get here in CA? Is it something else in my engine (spark plugs, fuel filter, air filter, excessive blowby, or ???)? Until I figure this out, running a more aggressive map such as the Cobb Stage 1 will only lead to more frequent detonation and the increased possibility of engine damage.

Saturday, November 13, 2004

Quote of the Day

"Patriotism means to stand by the country. It does not mean to stand by the president or any other public official. The president is merely the most important among a large number of public servants. He should be supported or opposed exactly to the degree which is warranted by his good conduct or bad conduct, his efficiency or inefficiency in rendering loyal, able, and disinterested service to the nation as a whole. Therefore it is absolutely necessary that there should be full liberty to tell the truth about his acts, and this means that it is exactly necessary to blame him when he does wrong as to praise him when he does right. Any other attitude in an American citizen is both base and servile. To announce that there must be no criticism of the president, or that we are to stand by the president, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public. Nothing but the truth should be spoken about him or any one else."

--Theodore Roosevelt

Friday, November 05, 2004

WRX Delta Dash Logging

I recently picked up an EcuTek Delta Dash so that I could start diagnosing the audible ping I have been getting under full boost with my Cobb AccessPort Stage 1. I've been uploading all the plots and logs along with comments about each one. I have also started a thread about the logs/plots at both NASIOC and Cobb's WRX Forum.

So far, all I have been able to determine is that my engine is not happy running the CA Stage 1 maps. Audible ping and an IAM of 8-9 == Unhappy ECU. EcuTek has a lot of information about how the Subaru ECU adjusts for operating conditions, if you're curious you'll find it very interesting.