Another Tephra Discovery:


Hi All,

I found this ages ago, but only just understand it now.

Now we all know that 0x24 (36) is the maximum knocksum the ECU will allow!

However this isn't the full story.

When you are UNDER the Load in the "Knock Load Threshold" table the ECU will actually use the following formula to limit your maximum KNOCK_SUM:

MAX Knock_Sum = 3 * (High_Oct_Ignition_Map - Low_Oct_Ignition_Map)

This is why when you increase your High Oct Map without touching your Low Oct Map you seem to get MORE knock in low load areas of the map.

It's not actually more knock - it's the same - its just the ECU is allowing more of it to be converted into "knocksum"

I dont know what this means in terms of tuning? I think it's best to leave the Low Oct Ignition Map alone anyways :)

But now you know :)

Cheers
D.

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damn, to many windows open, and I post in wrong threat. Deleted.