I've run into a dilemma the tacho output of my microtech don't work, and rather then senfding my ECU down to south australia to get repaired and end up with a big bill for such a small thing, I'm needing a bit of help, now I have a autometer tacho which is a direct ignition tacho (not an inductive setup like a standard 1200 tacho is)

I have 4 seperate coils, so I can't just simply hook my tacho up the the negative side of the coil.

My question is what is a direct tacho looking for?? As the way it's setup where it reads the signals it's tapping off the ground 12v and the signal so it has to be sensing voltage as to sense current the tacho would have to be in series with the coils power supply.

Why does the tacho need to go on the -ve side of the coil (when used in a conventional style enigne)??

my mate who swore black and blue (as he has a microtech as well on his SR20DET which is running sequential fire, so he has 4 seperate coils) that he just taped the signal off one of the coild and that was it. I knew it wouldn't work because in stead of getting 4pulses per rev it was getting one per rev, but i hooked it up that way and low and behold my tacho doesn't go above 1000rpm much, so as I suspected it's only reading a quarter or my rpm.


Now my solution is can i tap off each of my coil wirs from my ecu put a power diode on each so they don't all fire when one fires and then on the end of the diodes solder them all together and run that wire to the tacho???

therefore it should be reading the 4 pulses rather then one???

I know auto meter sell a box that fixes my problem but it's $160 plus postage and I think thats a rip off.

My coupe is in getting tuned at the moment so I can't try anything with my tacho at the moment but I'm confident my idea should work. A guy from auto one told me as I am good mates with him that this lancer had the same setup and they put a resister across a 12v signal and joined that to one of coil wires and it worked. I was quite amazed that this could work I thought it would sit a certain rpm and move maybe 1000rpm aound that point.

tnayway thanks for listening I hope some elecronic guru's out there can help me as I tried searching the net for info but came up with nothing.


Cheers
Damo