DOD and Knock Retard

[arthansen]

On my 2008 G8 GT, I noticed that I am getting a lot of Knock Retard while the DOD (Displacment on Demand) is active. Check out the attached log file.

Though knock retard in DOD is not a bad thing in that I am never looking for power while in DOD, the problem is it forces the spark down to the Low Octane table. You will notice that at times, the Knock Learn Factor goes as high as .4.

Now for the question. I want to set up a histogram to track this but because I only want to track it while in DOD, how do I filter so I only see DOD info? The problem is that the Fuel Cut Type PID is how to identify that but it is not numerical. Any sugestions would be appreciated.

[Pro Street]

My 09 G8GT does it too! I looked at your scan and I think mine is worse than yours!

[bluegoat06]

Are you logging with a WB ?, are you still using the stock tune ?

I don't know if you can perform this procedure with DOD, i don't have any experience with DOD cars, but if the stock knock settings in the G8GT are similar to the LS2 GTO's, then you could try the following,

Go to Spark Control, then Spark Retard

Double the Knock Retard Decay / Decay Rate (Entire table Multiplied by 2)
Halve the Knock Retard Attack / Base Retard (Entire table Divided by 2)
Halve the Burst Knock Retard / Retard vs Cyclair Delta (Entire table Divided by 4)

Again, i don't know if this settings would work as expected while on DOD, so i hope somebody with such experience would chime in and confirm.

[arthansen]

It is still stock and I have not hooked up my WBO2 yet..

Luckily, there are 4 main spark tables. High/Low and High DOD/Low DOD. I should be able to modify the spark tables to eliminate the DOD knock. Amazingly, the High DOD table actually calls for more spark in most cells then the High table does.

What I need is to be able to filter out the non-DOD info so I can identify the cells that are giving me DOD knock.

I guess, since 95% of the knock comes from DOD, I can just look at the overall knock histogram and use that but I would love to be a little more precise.

[SoCal]

This is an old thread but seemed the most appropriate place to mention something I noticed recently. Started to pay attention to Knock Learn Factor. As a lot of people have experienced, I had knock in DOD. But hardly any when DOD was inactive. Looked through some logs and went to take a little timing out of the trouble areas I was seeing. (~1600 RPM, 0.24 g/cyl) Noticed the HO (DOD) and the LO (DOD) timing tables had the same values in that region. That seems like a recipe for constantly bumping up Knock Learn Factor. If you experience knock there, Knock Learn Factor is likely to go up. Then the next time you return to that area during DOD - even if the Knock Learn Factor is higher now - you still get the exact same timing as the last time - both tables are the same (in that area) so it doesn't matter which one you are favoring. If it gave you knock then, I'd expect it to give you knock now, too. And so up goes Knock Learn Factor.

Just checked the regular High Octane and Low Octane tables. Same thing there. The top several rows are the same in either table. Maybe that high up on the table is such light load that it doesn't matter. But if that is true, it doesn't seem right to let it affect the Knock Learn Factor.

This is in a 2009 G8 GT.