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Knock Detection

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Hi Guys.

I'm having a bit of an issue with the knock detection/control setup on my early-model G4 Xtreme (5100-series serial number)

When I go to configure it both the options for the Xtreme and other ECUs show up rather than only showing up the relevant ones, this is somewhat confusing and probably a bug.

My second dilemma is that the engine in question is a Subaru EZ30D (05-06), I'm not sure if these knock sensors are compatible, however the calculated estimated knock frequency is around 6400Hz. This is nowhere near any of the available settings on the Xtreme, which would be best pick? With either 5500Hz or 7000Hz I'm picking up knock where I believe the engine is not knocking, and not even getting the slightest change in the level when I intentionally induce low RPM/high load knock.

Your thoughts are awaited with anticipation.


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Hi Cam,

Are the knock modes you have showing the following?:

ON - Knk Internal

ON - AN Knk Interface

ON - DI Knk Interface

If so these are all the modes available on the G4 Xtreme. The Internal mode is for using the inbuilt knock detection circuit, the AN and DI interfaces are for using external knock detection devices such as the G4 KnockBlock.

In 2000 a lot of Subarus went to having 'second harmonic' knock sensors. These are not compatible with the knock detection on the G4 Xtreme. The easiest solution is going to be for you to replace your knock sensor with a bosch 'donut' style knock sensor. An alternative solution would be to use a knock detection device like the G4 KnockBlock that can work with second harmonic knock sensors.



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I'm using Knk Internal. 

I have switched the sensor out for one from a 1990 Legacy which seems to have caused some improvement, however I'm still not seeing readings over ~77 (with gain x1.5, the max for the Xtreme) for what I assume is severe knock. And I still see nothing recorded at Low RPM/High Load, despite being able to hear the clattering.

Based on the above information I'll replace both sensors with earlier ones and wire them in properly. However this still doesn't answer my question about the frequency filtering.... Which setting is best for a 6.4khz knock frequency (i.e. what are the attenuation slopes on those filters)

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Hi Cameron,

The best knock setting for your application based on calculation would be the 7000Hz setting. The -3dB points on the filters are approximately +/- 1kHz around the center frequency. Although I would recommend testing each of the frequency settings to see which gives the best result.

You can try fitting two Legacy sensors and see if this improves the situation, but I would reccomened for best results use the Bosch knock sensor as this is the particular sensor that the system is optimsed for.



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  • 3 weeks later...

Hey Cameron,

Dave at D-tech informed me that the later EZ30 models came with 2nd harmonic knock sensors and so arent suitable for use with the G4 as stated above.  I run a pair of early EZ30 sensors (pre-2003) which seem to work correctly.  I do get a bit of a noisy signal around 4,000rpm but they do the job nicely everywhere else in the rpm/load range with pretty much default settings.

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