Knock Counts

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Nov 29, 2014 | 02:19 AM

C4ProjectCar

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From: Lynchburg, VA

Knock Counts

I just got ALDLDroid and a Bluetooth ALDL adapter for my '90 6-speed coupe, so I've been looking at the ECU data.

I noticed to my surprise that I am getting knock counts. I have never heard spark knock in person, but nothing about my engine sounds abnormal to me.

The knock counts start out at 0 and climbs as the engine runs. By the end of a short test drive today it had risen to 8 counts. One data log from the other day shows it getting up to 28.

When the computer detects knock, it is supposed to retard the timing accordingly, correct? The logs show that the knock retard spikes when the knock count rises at all (or sometimes immediately before that happens) but then drops back down to 0.

I filled it with 91 octane just in case (I had been running 89) but it's still an issue. Any ideas?

Nov 29, 2014 | 02:36 PM

MrWillys

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From: Reno Nevada

It is functioning normal. Don't get freaked out by it unless it becomes excessive. 28 is very normal.

Nov 29, 2014 | 04:37 PM

C4ProjectCar

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Drifting

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From: Lynchburg, VA

Quote:

Originally Posted by MrWillys

It is functioning normal. Don't get freaked out by it unless it becomes excessive. 28 is very normal.

Cool, thanks.
Any idea why the ECU pulled timing each time the knock count rose? Is that just normal programming?

Here's a picture of the datalog so you can see what I mean. Blue is knock retard and yellow is knock count.

Nov 29, 2014 | 07:03 PM

MrWillys

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From: Reno Nevada

Look at your maximum knock tables and you'll see it is just pulling a little. It can be a pothole in the road too.

Nov 29, 2014 | 08:12 PM

bjankuski

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From: Glenbeulah Wi

Quote:

Originally Posted by C4ProjectCar

Cool, thanks.
Any idea why the ECU pulled timing each time the knock count rose? Is that just normal programming?

That is normal programming.

Nov 29, 2014 | 11:10 PM

C4ProjectCar

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Drifting

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From: Lynchburg, VA

Quote:

Originally Posted by bjankuski

That is normal programming.

Just out of curiosity, what is the purpose of pulling the timing but then restoring it immediately?

Nov 29, 2014 | 11:12 PM

C4ProjectCar

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Drifting

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From: Lynchburg, VA

Quote:

Originally Posted by MrWillys

Look at your maximum knock tables and you'll see it is just pulling a little. It can be a pothole in the road too.

I'm entirely new to the tuning side of things. Where would I find the maximum knock tables?

Nov 30, 2014 | 10:16 PM

bjankuski

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From: Glenbeulah Wi

Quote:

Originally Posted by C4ProjectCar

Just out of curiosity, what is the purpose of pulling the timing but then restoring it immediately?

The computer is always trying trying to get to its programmed spark timing, (For max performance) if there is no spark retard detected the computer will add in any spark that was pulled before. As far as the engine is concerned the timing is pulled out very fast and added back in slowly.