A request to the technical experts among you:

Who has experience with using RON 95 and RON 98 octane (EU figures) with regard to engine knock of the 5-cylinder engine generation?

My experience: Using 95 RON and accelerating in 2nd or 3rd gear (MT normal aspirated) from about 1000-1500 rpm, you can clearly hear the anharmonic knock sound. (Btw: you can only hear it when the window is open). Using 98 RON under same conditions there is no knock audible.
I know that for the ECU to react, the knock sensor must first detect knock, before the ECU retards ignition. Is that what I actually was hearing?

How do you know the knock sensor is really working?
Is it normal that you can actually HEAR (at low rpm) the knocking before the ECU reacts?
Is the ECU able to recognize failure of a knock sensor? (i.e. can I trust the ECU, when no warning message/ VADIS fault code appears?)

Thanks in advance for your comments!

Wasn't aware that the Volvo's had a kock sensor. My ex-girlfriend had a pretty reliable kock sensor. That's why she's the ex...She sensed a lot of other kocks out there.

Sorry, just couldn't let it pass.
--
1998 S70 T5

Oh, Oh, what a difference an "n" can make. I saw it just too late. Hope I'll get some serious answers though...

Greetings,

D