The knocking sensor sends the information to the ECU which then reduces the ignition advance (timing) to stop the knocking. Knocking occurrs when the explosion takes place before the piston reaches TDC (top dead center) and is quite a descructive phenomenon for engines. If not controlled is usually creates holes in pistons. If you've driven the car for any length with this noise then it's doubtful that it is actually caused by knocking - you'd have had all sorts of problems after not many miles.

it's because of this that I'm hesitant to start the mods. I can see myself completely invalidating the warranty by fitting something arbitrary like a cone filter, and then getting the news that my top end is in need of replacing...

I think my "pinging" may be slightly different??

It only makes the noise when the Air Con is switched on - switch it off and it dissapears completely??????

Still going to take it in, but it definately seems to relate to the AC

It may be the petrol, our quality is rather sh**ty! & we only have 92 octane...also, I heard that we (SA guys) should only use BP (heavy metal free) cos the metals in the other petrols do cause prob's over time. I know with my previous A3 Turbo Audi said BP was best. And BMW had prob's with cat's giving in etc. cos they became jammed etc with the metal particulates in other petrols...I know that by the beginning of 2006 ALL petrols in SA have to be heavy metal free...the pinging may be related to petrol then (directly &/or indirectly), but not sure...

it happens when I use BP too...

then mayb its the octane...? i dunno, mine is fine, mayb i'm just lucky...

The ST is calibrate for 95RON fuel, run it on lower RON fuel and you will get some light detonation on load changes. The knock control should take care of the steady state igniton timing, but you will never get rid of the splash det unless you use the right fuel.