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Knock Link (light) question


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I have recently installed one of the G4 Knock lights in my R33 Skyline. Firstly was just checking its normal  for the light to go through its sequence "dim blue, flashing blue then green" before the engine has actually started? Ie if you turn the ignition to on position (light powered) then happen to not start it very quickly itl be lit green before then engine has been turned over/ started? I know you could just turn the key straight to start and that would probably solve this just thought worth checking thats normal?

Also I get quite alot of red flashing light at random places. I suspect its interference or my engine is too mechanically noisey (built RB26)?! As the red light sometimes occurs at idle and or low rpm down shifts etc and not twice in the same place/rpm that I can identify really (except for idle). Fairly sure it is grounded correctly as I bought the link sensor and loom with it too. (Note: tuner tuned the car after light installed with his knock phones and still does it)

Thanks for your input,


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  • 2 weeks later...
  • 1 year later...

Same here. Green light before start if starting takes too long and random red light flashing while running. Build is 5.7l(350cid) blown with weiand 144 charger. Innovate wideband doesnt give any hint for knocking and i do accept idle red flash because natural sound of charger.


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I Connected it to parking lamp wire so i could eliminate sounds of starter, this was recommended by friend, who had recommendation from someone... His light seems to work ok. I can try to connect it even straight to battery. Should i use some shielded cable with sensor? Im now using original wire, because it was long enough. Just lenghtned + and - cables. I was happy not to fiddle with sensor wires for nothing? It would be helpful if operation logig would be explained somewhere and wire reguirements were more clear, like are oem wires shielded, or does enduser need to prowide shielding... And no, it dosent make any difference if i first turn lights on and activate knocklight, or start the engine first and then pull lights on, which starts knocklight. At this stage its not really useful device to start tuning ignition timing, for me at current setup atleast... Oh, one more thing, im using bosch 2 wire sensor, with both yellow and green wire connected.

Thx for replys

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As per the instruction sheet the red wire needs to be connected to an ignition switched source that stays live during cranking.  Park lamps are probably an ACC circuit that gets disconnected during cranking. It needs to see the drop in voltage to detect starting and then alternator ripple to detect RPM.

Also as per the instruction sheet the sensor wires need to be shielded.  I have no idea if your OEM wires are or not.  

When driving/running the knocklink builds a 2D noise Vs RPM (alternator ripple) profile into its memory. There are filters and other logic used to focus the "listening" more to typical knock frequencies rather than just general background noise.  The engine must not be knocking when the device is learning the noise profile.  Any noise event that it sees significantly higher than this learned noise profile is assumed to be knock.   Since mechanical noise is mostly directly related to RPM the 2D profile will generally work well.  

But, it is not foolproof, as with any knock system, any irregular noise that occurs randomly and unrelated to RPM may not be masked by the simple 2D map.  For example gravel hitting the exhaust system of a rally car, a jet boat hull pounding on the water, heavy piston slap or flat tappet noise that is variable from hot to cold etc.  

Since it uses alternator ripple to determine RPM, the engine must have an alternator, the alternator needs to be driven by the crankshaft and the device needs to be connected to a power circuit that sees the alternator ripple and start up voltage drop. 



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  • 6 months later...

I have a knocklink G4 light and on startup it goes from blue to green. I've never seen it go red which i'm presuming is good, but does this mean that all is working good and I have no-knock or is there a way to test it?

I'm pretty sure i've wired it correctly and I have shielded the wires, also using a bosch donut 2 wire high res separate sensor.

Just had another look and powered the car on but didn't start it, light flashes blue a couple of times and then green then stays green.

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