Understanding Knock Retart

[als008]

Hey guys so ive finally started doing some basic tuning on my 2018 GT. I know this may seem like a stupid question but I wanted to clarify. Negative knock on the scanner means the ECU is adding additional spark or pulling it. I know this sounds contradictory but an online webinar I recently watched show that then the KR went Negative they were saying to ADD spark back in.!!

Hope this makes sense. Ive attached a log file for reference. As you can see at some light throttle accel (< .5 Load) im seeing upto -6 Knock. and same as the WOT pull upto -4.


Any advice on this.

Cheers Allen

[Bill88stang]

On these vehicles negative knock is good its showing how much the computer is adding timing, positive is bad that's timing being pulled back due to knock whether its real knock or false knock.

[als008]

Thanks for the reply Bill, I know it seems backwards so good to have confirmation on this.

[Thatwhite5.0]

Kind of backwards. If the number is negative, you have negative knock present, there is no knock present, no sensing of spark knock so the sensors are adding -3 degrees.. It's like a confirmation.

Positive number shows it has Positive knock. Positive, for sure you're knocking 3*.

These PIDs aren't something you'd want to make a histogram and start adding to spark tables. They added a new channel some time ago called "Knock Correction" your strategy may or may not have it. It's opposite of how I explained and normal to how a lot of tuners know and read better.

[als008]

Well I guess its kind of backwards Logic to me. When I look at Fuel Trims for example, -Neg fuel trim means ECU is removing fuel to meet Commanded and +Pos Fuel Trim means its Adding Fuel. This logic makes sense. So when I saw the first Logs I did and it showed -3 Knock Retard I just assumed it was same logic - removing 3* of spark!! Thanks for the replies guys its all starting to make sense now.

[blackbolt22]

Well I guess its kind of backwards Logic to me. When I look at Fuel Trims for example, -Neg fuel trim means ECU is removing fuel to meet Commanded and +Pos Fuel Trim means its Adding Fuel. This logic makes sense. So when I saw the first Logs I did and it showed -3 Knock Retard I just assumed it was same logic - removing 3* of spark!! Thanks for the replies guys its all starting to make sense now.

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