I was taking a closer look at my spare S5 Mazda reman I got at the u-pull yard and noticed that the rotor housings have a threaded hole above the trailing plug. My S4 engien doesn't have these but I noticed the same holes when I was browsing Speed Machine's site and was wondering what they're for. I attached a pic of the ones at Speed Machine.

 

they're for the knock sensor. It mounts on the (rear) rotor housing in S5's instead of the center iron on s4's.

 

So it would only be used if I had a turbo rotary then? That's pretty interesting in any case.

 

all S5/S6 have the threaded housings.

 

do ALL s5/s6 have knock sensors though?

 

i've got en s4, is it better to have placed the knock sensor on the housing?

 

good question, i've only done a handful of S5 n/a engines and i can't remember if they have a knock sensor.