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

have you try the 4 diodos solucion that you presented?
this idea might work but you dont now which type of signal your tacho reads.can be negative input or positve input.i dont now if you have a distributor whit points?problemy not.if you have try this:conect the tacho to the points and disconet the coil wire to the distributor.only the tacho to the points.
start the engine .whill not start but look to the tacho .if he moves then is negative input.
the diodes solution not work.if he doesnt move then is posite input and the diodes solution might work.test this whit a "normal" datsun whit points distributor.

thanks for yout reply.

No I haven't tried the 4 diode trick yet as my car is getting dyno tuned at the moment.

I've got the tacho signal wire at the moment hooked up to one output for spark from my ECU (which my friend strongly suggested i should do).

I was just after some info on how the tacho actually works as no one on the internet says.
I don't have a distributor anymore I run a Cam angle sensor (as it reads the cam not the crank)

Cheers
Damo

Sending your Microtech to SA will only make the bill higher , since who ever you send it to will just send it to Microtech in NSW so Dom or Russell can fix it.

The tacho requires a negative pulse and as long as you wire the 4 diodes all the same way, facing the correct way so they dont feedback signals to the other coils, it will work correctly.

thanks phunk

What would the autometer tach adapter as they call it do??? The same thing I'm doing just in a box with an autometer sticker??

I dont know. But if it takes a trigger from each coil negative I would say yes. Being Autometer, I would think it also has a fluxcapacitor in there too.

the same one in the dolorian in back to the future????

Notice trigger taken from all coil negatives.
Does the autometer one promise time travel?

hahahahaahhaahaha CLASSIC!

What is this picture of???? Please tell me it's not from the actual car used in back to the future??
What worries me more is you have this picture ...


Keep it up phunk you crack me up every time with your pics and posts. I dunno why people on here have a barney with you...

Cheers
Damo

Yeah thats the delorian's flux capacitor
Its amazing what things stick in my memory and its amazing what you can find on the net.

As to the other part of your post. I guess some people dont have anyone to hug and thats why they look for Barney with their tag along friends.