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Knock Ignition trims very low when using Normalised Knock


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V42 Normal test.llgxV42 absurd test.llgxHello,
I've fully mapped my Mini R53 using traditional knock detection (ignition only). Everything works well and ignition trims are coherent when knock level is above knock threshold.

Then wanted to try Normalised knock and I'm facing a weird issue : when knock level is above knock threshold, knock ingition trims are moving but instead of seeing 1.0 deg/knock event of igntion retard as calibrated, I see only 0.1 knock I-trim.
I thought I had some gain to adjust but I found nothing.

Then I tried to make an "absurd" test by setting the knock threshold very low compared to normalised level, and instead of seeing very high and sudden knock retard, I only see the knock trims slowly ramping up.

To sum up : when I use Normalised knock, I see knock Ignition Trims being about 10 times less as they should be (0.1deg of retard instead of 1.0 deg of retard)

Am I missing something here ? All the gains look well calibrated, I don't understand...

PS : I see knock events counter incrementing as it should

knk level 1.png

knock detection.png

knock setup V42.png

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The amount of retard you get is based on 3 factors.  "Knock level detected", "Ignition Retard Gain" & "Knock Trim Gain Table" - these are all multiplied together.  

"Knock Level Detected" is Knock level - Knock Threshold.  So in your first example on cyl 1 you have a knock level detected of 0.62 (1.62-1.00), your Ign retard gain is 1.00 and knock trim gain table is 1.  So you would get 0.62 x 1.0 x 1.0 = 0.6deg instantaneous retard.  

In the second example on cyl 3 you have a knock level detected of 0.18 x 1 x 1, = 0.18deg (truncated to 0.1deg).

With normalised mode a knock event will be a significant spike above the threshold so your retard would be more significant than your examples.  Looking through my maps with normalised mode I usually have a retard gain around 2.0-2.5 and my trim gain table is just 1.0 right across.

Below is an example pull from our subaru where I have put an extra 5 deg advance in a single cell in the ign table at 3500rpm to purposely make it knock (you can see where Ign angle bumps up as we pass through), Cyl 4 knocks, the ecu instantly pulls 4 deg out of cyl 4 and you see after that the cyl 4 noise level drops back below the others.   

Threshold was 2.8, knock level was 4.64, gain was 2.5 (I have the retard limit set at 4 in this car).



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Hi Adam, thank you very much for this explanation.
I think I was tricked by the unit : Ignition Retard Gain 1.0 degrees/knock. Thinking that 1 degree would be withdraw per knock event.

I will give it a new try with boosted gains in Normalised mode.

Thanks a lot Adam

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