Knock Level Assistance 1JZ G4X (Signal Noise?)

[robrixon]

I'm after some assistance with an issue with the detected knock level and settings on the Extreme G4X on my 1JZ non-VVTi. My tuner was using an external knock detection box and headphones and confirmed that the engine was not actually knocking on this map.

The engine harness uses home runs of M25700 twin core for each Bosch sensor and the shields are drained to ECU B17 along with the Signal negative on both sensors. The front knock sensor Signal pos is going to ECU Knock 1 and the rear is going to ECU Knock 2. I have confirmed polarity and continuity for signals and grounds.

Based on the attached log, is this amount of RPM-dependent noise typical (or at least not unusual) and the gain(s) need(s) to be adjusted or do I potentially have a shielding problem?

Any help would be great.

 

Knock Testing.llgx JZX90 BTM90 Knock.pclx

[Adamw]

Your gain is too high - it varies a lot but from engine to engine but a more typical gain is around 1-2.  Adjust the gain so that at medium RPM/medium load your average knock level is around 100-300, and say no more than about 600 at WOT & redline.  

You will likely get less random noise using one of the narrowband frequency channels (I havent tuned a 1JZ so cant offer a suggestion from experience, just try the calculated value as a test).  I would also increase  your window start to 15 so you are only "listening" for knock after the TDC piston slap has occured and shorten the window length to 50deg.  

Once you have less erratic noise and a knock level profile that trends with RPM then you will want to adjust the individual cyl gains so that the knock levels of each cylinder on average are as similar as you can get. 

[robrixon]

Thanks Adam, setting the gain down to 2 let me adjust the threshold down to 600 at WOT and redline. I like the way the software interpolates the threshold between axis values so intelligently.