Shift Light

[Trip]

I am experiencing a strange problem in the high RPM range where my shift light and datalogger are not marking correctly the rpm. When I rev the car on neutral the dash dials and datascan show correct RPM almost up to red line. Though i noticed the needle flickering in the high rpm range when i am driving at WOT.

I was using the signal from the ECU to feed the shift light, datalogger and dash dials. So i assumed that the problem was the signal from ECU was not strong enough to feed 3 devices.

I moved both the shift light and datalogger signal feed to the MSD 6A tach output signal so i can split the load but the problem is still there. I tried another shift light with inbuild rev counter and i noticed that its accurate below roughly 5500rpm, after that it starts raising slowly and not syncronised with the engine rpm.

I am lost here since even my MSD tach output is giving me the same odd results. Could it be its not the signal which is screwed but something is flactuating in the power or ground feed ?

 

[Trip]

here is a small video clip i took with my phone. There is the shift light with digital tach getting its feed from the MSD and the OE gauge taking its feed from ECU. The higher the revs the more the discrepancy is between them.

Before anyone states the obvious, Both shift lights i tried and also the PLX datalogger are match with each other even when using ECU feed.

The OE gauge and Nissan Datascan are also consistent with each other. But not consistent with the 2 shift lights and datalogger. :der:

 

[Braveheart]

That is stange... maybe the gauge sensor is picking up inputs fron HT leads.
Try a suppressor on guage wires.... ferrite beed or a very weak magnet.

 

[Trip]

I would imagine the ECU determines the RPM from the CAS.


I have some ferrite beeds i can try out. thanks for the suggestion