[trahmah]

Sorry for the long winded subject. The conversion is all done and car works great, just can't get the damn tacho to work. I've got a g16b with custom Motec loom to a m130 but kept the old g16a loom for the dash lights etc. anyone have any experience connecting up an aftermarket ECU to the factory SE416 tacho? I'm using an SR20 crank angle sensor and 4x LS1 coils.

Thanks

[ozzycouch]

No experience with motec, but generally you should have output signal off the computer to directly drive the original tacho, or any tacho for that matter.
Have read about the outputs off the computer and go from there, you should already have the signal with a completed working installation.

[frak]

Well if a tacho is the old style designed to be driven by a tap from what goes to trigger the spark plugs then it wont notice the nicer looking waveform from an ecu.

You end up with no or almost no reading oj the tacho.

In which case some minor components added to the circuit can make the ecu signal spiky/messy enough to be noticed. Plenty of examples if you google it.


Or fit a modern tacho.

Not sure what type is fitted though. Plenty of efi cars had the older style tach and signal.

[trahmah]

Ok gents just though I'd provide an update in case anyone came across the same thing in the future. I had a chat to Alan at Rajab Racing Developments in Vic and he told me similar to what frak said. Some google searching also suggested that the older style tachs ran off of the back emf from the ignition coil. Alan's suggestion was to wire in pins 85 and 86 on a relay in place of the original ignition coil, and that seems to work perfectly.

[ozzycouch]

Didn't know the old tachos failed on a clean signal. Nice simple fix you found.