I can laugh too now, but I had to do the logging runs to convince myself that there was a substantial drop in output under WOT with lower octane fuel... A lot bigger than I was expecting. I dropped to standard octane for a while because, sadly, 95% of my driving is steady cruise. 

Good discussion, but I'm still seeking that elusive answer as to why LDRXNZK is higher, not lower, in the 1.8T variants I've studied.

Doug

O.k., so the answer is that the knock control retards timing to deal with knock on the crank synchronous pathway as fredrik explains, but more boost is allowed to mitigate the loss of power by sparking later than would otherwise be required for peak cylinder pressure as Giannis suggests...

If that's the correct then I'm a happy man!

If that's correct, why does the dumbass funktionsrahmen specify that LDRXNZK should be 15% lower than LDRXN?

Doug

Just a thought; I've had my cars software updated twice by Audi. This was well before I knew shit about "tunes", "chips", logging etc (some may argue that I still don't). If they were in fact updating it, I could only assume it was to run more efficiently than before. If this was the case, maybe they found a more efficient way to manipulate the maps? Again, just a theory....and in my defense I'm falling asleep at the keyboard, so this may read like nonsense in the am.

O.k., that's good enough for me. I've revised the 1.8T guide to read:

"Remarks for LDRXNZK: It is noted in module LDRLMX 3.100 that the values should be set about 15% lower than LDRXN which would be reasonable from an intuitive understanding; i.e. overall ignition advance is reduced during knock so maximum allowable cylinder charge should also be reduced. However, in these examples, the values in LDRXNZK are actually higher from around 2,300 to between 5,000 and 5,500 rpm. The only plausible explanation is that a slightly larger cylinder charge is allowed to counteract the sub-optimal peak cylinder pressure and consequential loss of torque that would result from sub-optimal ignition timing due to knock. Otherwise, the driver would feel a noticeable step-change in power during the onset of knock. If in doubt, don’t try to second-guess the OEM calibrator; follow the advice in the funktionsrahmen and set the values in LDRXNZK a bit lower than LDRXN."

Thanks guys.

One issue I had which I failed to mention in the original post was that if there was to be a 15% or so difference between the maps with no other power-loss compensation, then the driver would feel a noticeable step-change in power every time continuous knock was encountered. That didn't seem correct and which, in part, caused my confusion.

Doug

I just made the same discovery on my AUQ engine. Thought I had the tables mixed up at first, but when I log the requested engine load it clearly follows the shape of the lower one (LDRXN), and this was during cold conditions with 98 octane fuel.

Link to my thread for reference:
http://nefariousmotorsports.com/forum/index.php?topic=1534.msg14573#msg14573