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Understanding Knock Log Data

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First post here, & was not sure where to post it.

Andre, I did take you're Link G4 Plus Tutorial. It was very helpful. I've also learned much from the webinars, Thank You......

I have a 2003 Nissan 350Z (Full Weight-Interior) VQ350DE CP Pistons 11-1, Carrillo Rods, Head Work, Alloy Valves, 272's Kelford Cams, Vortech V7 YSi-Trim

This Log is on 93 Octane, Blower Pulleys are set for Low Boost. ( Blower Speed about 64,000 @ 7500rpm )

Drag Race Tune will be on C16 or Q16 on High Boost ( Blower Speed about 76,000 @ 8000rpm )

This is a Street Car that will also be Trailered to the Drags 1-2 times per years.

I'm just in the process of setting up Knock Control. I have watched HP Academy's 049 (setting up knock control) 6 times.

I do not yet (but will soon) have audio knock. So, I'm, Learning to interpret the Data.

I have beed in the process of Tuning in Vac-5psi & under 4000rpm max, but, most below "0" psi area.

My knock log (Top pic) shows: 2000-3500rpm & 18 in vac-2.6psi with 30-34% throttle, in 5th gear. Driving it very easy. All thru this area Cyl 3 has many spikes, Cyl 5 two small ones. Is this what False Knock looks like? Or? Motor sounded fine.

Also, in another area (Bottom pic) where there were peaks above the other Cyl's, but no where near the Threshold, the ECU pulled Timing, or at least that's what the Log showed. What is going on here?

Just some backround, Please forgive me as I'm a very Old School, X-Automotive Mechanical Design Engineer. My Dad taught me how to Tune Race-Car Motors in the 60's & the biggest lesson was about Detonation & how it Kills Motors. He taught me how to listen & I've have not lost a motor from detonation yet. But, I also want to grow too, it's just new for me.



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hello generally when I see this I would remove the timing by 5 deg on that cylinder in this area of the map clear the knock ignition table and drive the engine to see how the knock compares to the previous log you may from that be able to see if it is a false knock or is actually an issue if the knock level still shows spikes like this to this sort of level i would be pretty safe to say it is false knock but still follow thu with further testing,

most often I would also pull the injectors clean and refit them incase that particular cylinder is running a little leaner causing the knock as this engine is normally very even in noise,

Regards Ross

That's great advice Ross, and a good way to diagnose the problem.

Thanks so much,

Tim :)

Hi there!

In addition to the great advice already provided my two cents:

I would drive the car to a low load area and record the knock data. When when looking at it adjust the cylinder gain in the way that all cylinders show the same noise. Please see the screenshots attached. One thing that i found out is that with a throttle lift, there is chatter from the engine/gearbox which often can be interpreted as 'knock' but is not. The knock sensor still is just a microphone. With the VQ's i have seen a lot of extra noise from cil 6. Which is often one to pay extra attention to.

Kind regards,


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