Phormula knock headphones not hearing knock

Hi,

I'm new to the tuning world, but I have managed to get my AFR's and boostcontrol working quite nicely. I've also setup knock control on the Link G4+ Plugin ECU for my 1998 Subaru Impreza EJ20G to prevent knocking from destroying my engine. But when it detects "knock" with the exhaust valve closed, with about 0.75" exhaust opening remaining, decreasing the timing does nothing... Only lowering boost helps.

Opening the exhaust valve makes it a straight thru 2.5" exhaust and I have a second fuel, ignition and boost table that is linked to an input for when the valve is in straight thru mode. But I feel like I can get a better timing adjustment then the base tune that was included on the ECU. However my G4+ is detecting knock very suddenly at 5k RPM @ 1.2 bar boost no matter what the ignition advance is, with the valve closed. If i listen to the knock with the Phormula headphones, I can not hear it knocking at all. I can't seem to detect knock with this system, the knock sensor is installed in the factory location... It was a pain in the but to clean the area and to get it installed though. Would it be possible that a bit of dirt is limiting my abbility to hear any knock occuring? I can clearly hear the background engine noise though...

I've tried 70° advanced timing on 0.8 bar at 4k rpm and it sounds exactly the same as having just 10° of advance, so I'm really at a loss here... It seems like it cannot detect knock, and I'm not brave enough to try a higher load/rpm area to get a better chance of actually making knock...

Does anyone have any tips or experience I can use here?

I haven't used the Phormula knock detection system so I can't speak from personal experience however I know that many of our members have found it to be great. If you have the ability to try different frequencies or filters I'd test that because you may find you get a clearer signal. I'd doubt that some dirt would affect the knock sensor performance however it is possible as the knock sensor relies on being mounted solidly to the engine block so vibration can transfer into it.

I would be a little careful running a valve that restricts the exhaust down to 0.75" as this is incredibly restrictive and will have a serious impact not only on engine performance but also on your tuning. In my own experience restrictive exhaust systems on a turbo engine do make the engine much more prone to knock.

To test the knock audio you don't need to be using anything like 70 degrees advance, and in fact massively over advancing the engine may result in no knock occurring. At 4000 rpm and 0.8 bar you should be able to get knock on pump gas with perhaps 30 degrees or thereabouts.