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dp_tech

Knock Control Settings

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Hi all,
Can some to explain me, "knock windows" settings. In the manual says: "The engine position in degrees after the ignition event at which the knock window signal will start.  e.g. If the current ignition timing is 15 degrees BTDC and the start point is set to 10 degrees, the window will become active at 15 - 10 = 5 degrees BTDC" but why the window will become active at 15 - 10 = 5 degrees BTDC?
How I see this feature: The start window value this a start point in deg for window? Windows length - this is a total window line segment? e.g. I want to watching the knock within this "segment" 15 deg BTDC to 50 deg ATDC.
For this example the settings should be like this: Window start  at 15 deg, Window lengths at 50 deg, is it correct?

Regards
Pavlo

Edited by dp_tech

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Hi Pavlo,

No the knock window cannot be fixed in relation to TDC within Link's current knock control implementation, the window position follows your ignition timing.  In the couple of engines that I have seen running with cylinder pressure instrumentation I can say that the detonation position does usually have some relation to the ignition event so I think this strategy will probably work better than having a fixed knock window position like some other ECU's do.  There maybe some odd applications that I haven't considered though - can you explain why you think you need a fixed knock window position?

To give an example of how it works now, If we have window start set to 10 and window length is set to 50;

Lets say at 3000RPM & 200KPa your ignition timing is 30°BTDC, then the knock window would be active 20BTDC to 30ATDC. 

Now we increase engine speed to 5000RPM & 400Kpa and your ignition timing in the table is now 15, your knock window will be 5BTDC to 45ATDC.

 

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Hi Adam,

Thank you for reply and good explanation!
I have so far learning this ECU and for me is hard to say if the fixed knock windowing better than float, but I think the last one is much precise.

Regards
Pavlo

Edited by dp_tech

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