Jamie Graham1436215400 Posted January 29, 2013 Report Share Posted January 29, 2013 Hello I purchased a Knocklink G4 recently with the additional Bosch sensor for my 1997 Nissan Skyline ECR33 (RB25DET unopened with bolt-on mods only). It was installed by an experienced mechanic/tuner who ran it up on the dyno to see how it performed against his professional equipment and the Apexi Power FC and factory knock sensors. Whilst on the dyno it was noted that the Knocklink flashed red when coming off the throttle sometimes. Link support were called and they informed the mechanic that this could be normal, expected behavior so it was left at that. When I picked up the vehicle I only drove maybe a block and stopped at the next set of lights when the knocklink flashed red. It proceeded to do this randomly and repetitively at idle and at various other throttle positions. I called support again and they told me to return the unit via the dealer (Tuspeed). I have returned the original knocklink but the replacement unit is doing the same thing. I have double checked +12V supply and a good earth... What else could be causing this problem? It's obviously not detecting knock. Further to this whilst investigating the wiring etc I noticed what appears to be unusual behavior: If I turn the key on without even turning the engine over the knocklink light does the following: red for a few seconds, then dim blue for a split second before flashing blue and then turning green... it appears to have detected engine start and then tuned itself in to nothing! It doesn't appear to be detecting 'knock' at this stage... There is next to no documentation or configuration. Am I missing something here? Any help would be much appreciated Quote Link to comment Share on other sites More sharing options...
Simon Posted January 30, 2013 Report Share Posted January 30, 2013 The way the unit works is that once powered it looks for noise on the knock signal wire to let it know the engine is running. If there is any noise on the signal wire when the unit is powered up it will run through the calibration process. This noise could be due to other devices in the car such as coils turning on, fuel pump, engine fans etc. Wiring to the sensor should be shielded, the ground to the unit will need to be very good also. Check the wiring is not running along or close to any high current devices that turn on with the key. What I suspect could be happening is the unit is calibrating to a non running engine and as such is much too sensitive. Quote Link to comment Share on other sites More sharing options...
Jamie Graham1436215400 Posted January 30, 2013 Author Report Share Posted January 30, 2013 Thanks for the reply Simon I understand what you are saying. I have ensured a good earth and moved the +12V from the original feed to another used for my wide band AFR. The shielded cable has been run all the way to under the steering column where it connects with the knocklink. Is the shield supposed to be grounded? If so where? The cabling doesn't run past any high current wiring, the loom for the coil packs or ECU, the fuel pump is fed direct from the battery via relay, no electric fans at start up. As for being too sensitive this is my second knocklink unit! I've spent a lot of time and money on this device and I need it to work as advertised please! Quote Link to comment Share on other sites More sharing options...
Simon Posted January 31, 2013 Report Share Posted January 31, 2013 Shield should be grounded at one end only, Ideal would be to tie it to the ground for the knock link as close to the knockLink unit as possible. Another test to try would be to power the unit direct off a battery out of the car to see if it still goes through the set up even with no sensor connected. If there was noise getting on to the signal both units would be effected the same. Causing both to end up too sensitive and then in turn giving false readings. Quote Link to comment Share on other sites More sharing options...
Jamie Graham1436215400 Posted February 4, 2013 Author Report Share Posted February 4, 2013 Update: The only solution to the issue of the G4 'tuning' itself into an engine that hasn't started was to supply a 12V feed from the battery. This is a bonus because the G4 is now on a switch so I can turn it off and don't have the thing flashing red in my face every 5 seconds whilst idling at the lights! However this hasn't fixed the issue of false knock warnings whilst idling and at any other throttle position. The G4 does appear to detect knock but gives a warning at such low levels of knock (normal in a tuned turbo engine) that it is basically useless. I have been trying to earth the shielded cable from the knock sensor only to find that it is not shielded (normal practise?) so the knock sensor wiring kit supplied from the Link distributor appears to be unfit for the job. Should I have been supplied with a shielded cable kit for the knock sensor? If so what are you and your distributor going to do about it? Quote Link to comment Share on other sites More sharing options...
Simon Posted February 4, 2013 Report Share Posted February 4, 2013 Hi Jamie Got your Email I will get some screened cable out to you to try. It is best practice to have screened cable for the signal. Chances are in most cases not having screened cable would not be an issue. However it is worth trying it to see if it can help in this case. Quote Link to comment Share on other sites More sharing options...
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