Motec and autometer tacho's

[bretty]

Hi guys,

I know it's probably been covered a heap of times but I can't find the exact answer that suits my application in regards to hooking up an autometer tacho with Motec ECU.
I have an RB30ET in an LC Torana and a motec ECU. I currently have a tacho hooked up to it and it works but reads very incorrect. I have snipped the wires so it's calibrated to a 6 cylinder.
I believe I have a coil negative type of gauge. I've read other threads that suggest using a resistor to fix this but the other threads had no tacho reading at all, I do, it goes well over 10,000rpm though so i know it's way out.

Will a resistor fix this? What resistor do I get? What else could it be?

Thanks

[MarkMc]

Hi Bretty,
The resistor is to pull the signal up so the tacho works if it is not working at all, this is usually for ECU driven tachos.

Can you see if the reading is out by a certain factor like 2x or 1.5x or something like that. Revthe engine to 2000, 4000 and 6000 and tell me what the tacho reads.

[bretty]

Hi thanks for the reply.

Unfortunately due to not having a working tachometer I'm unsure of where the engine is at so I can't rev it to 2000, 4000 or 6000rpm.
It should be revving at 3000rpm at 100kmh but the gauge says 5000rpm.

Is that of any help?

[bretty]

Can anyone help?

[MarkMc]

You have a working tachometer if you hook a laptop to your ECU. You need to give me an accurate idea of what readings the tacho gives at known RPMs.....need a few example RPMs.