Technical how to mount tachometer

[timvdl]

Hi everybody!

I bought a tachometer for 4/6/8 cylinder engines and I'd like to mount it in my Seicento 900SPI SX. Now I read here the Sei has a weird ignition system and you need to use a 2-cylinder tachometer. The guide coming with the meter says you need to connect the green wire (tacho signal in) to the coil negative (-) or electronic ignition. Is there a way to connect it to both coils, or do they have a shared negative wire or something? Or is it possible to connect it somewhere where both signals come from?

Hope somebody can help me

Tim

 

[rallycinq]

Try here

https://www.fiatforum.com/cinq-sei-technical/25960-rev-counter.html

Cheers

D

 

[rallycinq]

Oh, and by the way

Welcome.

Cheers

D

 

[Malin Dixon]

The coils share a positive connection. You can't just join them together, so you would need several electronic components to combine the signals to feed one tacho.

If the tacho is anything like the one that I fitted, it is quite easy to modify to work for 2 cylinder ignition systems. It only needed one resistor changed.

https://www.fiatforum.com/showpost.php?p=771563&postcount=135

I don't know what ECU connections on the seicento go to the coils, but you can trace it back to either coil.

 

[timvdl]

I connected my tachometer to the magical pin 23 of the 900SPI ECU, and he seems to work fine I thought the engine was running much faster a higher amount of rpm than it actually does The engine seems to be running fine too, but though I'm wondering whether it might be dangerous to use this way of connecting or not. I'm afraid the rev. counter disturbes the signal, causes a too big current, or something like that. Can anybody tell me whether that signal is important or not? Are there possibly risks for the engine?

By the way, thanks for the warm welcome!

Tim