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Standard Knock Detection, How Good Is It?


rollex

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Great post Luke, couldn't have put it better myself. Although in my own car, Knock sensors have been off for ages. I believe that oscillations in the timing curve (caused by false knock/and my forgies) hurt average power at the track. There are a heap of tables that apply to knock sensors, nearly all of which I don't have the gear to correctly calibrate. I've seen quite a few tunes now, it might be something to do with a few of the tables not crossing over into HP (which I doubt) but it seems some tuners are using the knock sensors to trim the final ignition timing and could not possibly be logging the timing curve to compare against the desired maps in the tune. Apart from the whole dyno x vs dyno y variances etc I think that this is the reason some cars make good hp on the dyno but don't perform well at the track. I can't prove that though as I refuse to tune anyones car that way.

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I've always been curious how this works as well.

The figures in colour, are they the timing positions?

Does delay mean time and recovery mean advance?

What I'm trying to say is I don't understand what those figures mean or how they relate to each other.

Forgive my stupidness!!!

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Captain I believe delay time would be like a deadband, eg it keeps the retard at x degrees for that amount of time, if no knock is detected it adds the retard back to the timing.

Recovery rate would be how many degrees it "recovers" each delay time seconds. I imagine each time "knock" is detected it increases retard by 1 degree as there is no table to specify how much it pulls each event, perhaps it is multiplied by how bad the detected knock is.

How is my guess ralph?

Excessive spark retard generates a lot of heat and can be as harmful as knock.

Basic spark retard tables from a BF F6.


attachicon.gifScreenshot_2014-10-02-21-16-48.png

attachicon.gifScreenshot_2014-10-02-21-16-41.png
attachicon.gifScreenshot_2014-10-02-21-16-35.png

14 degrees of retard at peak torque is a sh*tload, that should stop even the worst pinging, if you've got a lean out bad enough to still ping with 14 degrees taken out then I doubt the car will even be running.

Do you agree?

Great post Luke, couldn't have put it better myself. Although in my own car, Knock sensors have been off for ages. I believe that oscillations in the timing curve (caused by false knock/and my forgies) hurt average power at the track. There are a heap of tables that apply to knock sensors, nearly all of which I don't have the gear to correctly calibrate. I've seen quite a few tunes now, it might be something to do with a few of the tables not crossing over into HP (which I doubt) but it seems some tuners are using the knock sensors to trim the final ignition timing and could not possibly be logging the timing curve to compare against the desired maps in the tune. Apart from the whole dyno x vs dyno y variances etc I think that this is the reason some cars make good hp on the dyno but don't perform well at the track. I can't prove that though as I refuse to tune anyones car that way.

I know in old nissans they disabled knock detection over 5500 rpm as the amount of engine noise they make they could no longer reliably detect knock, old motors with rattling heads and noise from the bottom end due to forged pistons etc may also generated false knock readings.

Personally I am of the opinion you should do your tune with knock detection turned off and with knock ears on your head so you know if it is knocking, then when everything is finished turn knock detection back on, confirm it isn't active all the time, then save the tune.

Otherwise how do you know if your tune is only working because the knock detection is pulling timing constantly? you definitely don't want that, then you have no protection as the tune has been pulling the max knock retard the entire time. I would absolutely not be surprised if there are aftermarket tunes getting around that only work because of the knock detection.

Edited by rollex
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  • Moar Powar Babeh
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I'm not i'm bullshitting.

I was sitting on the couch watching Orange is the New Black with my wife when I posted those shots, so I used teamnviewer to log into my server and screen capped on my phone. I would have been shot for stopping the show to do silly car stuff.

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Lol u had me... I was gonna question it cause it looked all the world like you were running vcm on the phone which would require a bit more than just an app...

The trust is gone...;-)

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