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Knock control

Posted: Tue Jan 31, 2012 10:15 pm
by engjoo
May I know what does "Knock control" in the datalogging means? I did a RTS followed by a datalog this morning on my car (FD2R) and noticed that it is always in 95-100% range. On the other hand, my tuned maps fluctuates between 0% to 50%.

Re: Knock control

Posted: Wed Feb 01, 2012 9:09 am
by Hondata
Knock control is related to the ECU's estimate of the fuel octane. Normally it will decrease without knock, and increase with any knock.

Re: Knock control

Posted: Wed Feb 01, 2012 10:22 am
by engjoo
Hondata wrote:Knock control is related to the ECU's estimate of the fuel octane. Normally it will decrease without knock, and increase with any knock.
Do you know why am I seeing such a big difference in knock control between RTS and my hondata tuned maps ? Are the native knock tables the same between stock ECU and one that is reflashed by FP?

Re: Knock control

Posted: Wed Feb 01, 2012 7:40 pm
by InsightRacer
(Just responding in the hopes that I might learn something)

FYI, on the CR-Z, a K.Control of ~100% is what you get with regular gas (87 Octane US). 93 Octane gives a K.Control of about 66%. On the CR-Z it looks the same on the stock (RTS) tune and Honda's stock tune.

As Hondata said, its the ECUs estimate of Octane level based on knock sensing. When it pushes the ignition forward and it detects knock, it ups the K.Control and backs of the ignition (using K.Control).

Assuming your gas is the same, it follows that you are generating more knock. That can come from 1) more ignition advance on the stock (or less on the tuned), 2) changes in the knock limits or 3) more knock sensitivity (higher sensitivity value(less sensitive) on the tune).

I couldn't figure out which configurations went with the FD2R but if you compare the Hondata stock configuration with your tuned configuration (File/Compare), you can see which tables have changed. You can them look at them (I find bringing them up in two different windows helps) and see if any of the ignition parameters have changed that would cause it to be more sensitive to knock.

And if that doesn't work, then maybe the stock is just different. You can kind of tell the stock parameters by looking at IGN, K.Retart and K.Control in the log but it's difficult to interpret.

Re: Knock control

Posted: Thu Feb 02, 2012 9:10 am
by Hondata
If you graph the knock control you'll see that typically it only goes up with knock, which often results from only one small area on the tables. If you reduce the knock ignition limit in those areas, you knock control should end up lower.