RPM signal to VEMS WBO2&EGT gauge, problem

[ranz]

I have an VEMS WB&EGT gauge and I want to add RPM signal for logging. I know witch cable I need to connect it, but i get very jumpy reading... it shows me RPM between 200 to 1300. Does anyone know what I need to configure to get correct reading? I read the vems WIKI page, but I don't understand very well what needs to be done

[Flat on my back]

.

Sounds like you have noise interference on the rpm signal line.

Check you have made all the earth connections and you may also need top use 'screened cable' for the signal line.

Do you have an oscilloscope to monitor the line with?

[ranz]

Yes I have an oscilloscope, I'll try to check with it the signal.
But original cabel from plug to ecu is also not screened, how does that work then?

[GazzaG60]

are you using VEMS?

with VEMS in order to get a clean signal you need to change the polarity on the secondary VR sensor. not sure if it would but maybe the gauge uses the same logic and needs a reversed polarity.

theory. i dont use the RPM signal in the gauge.

[ranz]

No, i'm running on stock ecu.
I'll first try measure the signal with osscilloscope and let you know of the results.

[ranz]

Tested it, oscilloscope shows no interference in signal, signal is same at the sensor plug and at gauge plug.

[gnutz2]

Try putting a variable resistor inline on the rpm signal from the ecu to the gauge, say a 10k (make sure one of the two wires is the wiper).

Then try turning the pot while driving the car.

This has worked for me before

[ranz]

I will try it when I get my car back from bodyshop and let you know, thankyou.