4 coils tacho

[Hen]

LeeRoy - The problem is that with a single coil and dizzy arrangement, the tacho sees every firing of the coil, so 4 per cycle. But with 4 coils, if you just connect a single one to the tach, it will only see 1 spark per cycle, so I assume it will read 25% of what it should.

The diode arrangement above allows the voltage spike through from each coil, but doesn't let the spike intefere with the operation of the other coils. I've installed a twin coil version (ZE in AE86) and it works very well.

Timbosuarus - Old tachs work on the voltage spike which occurs when the points open (result of cutting the current through the low tension side of the coil)

Hen

EDIT - beaten to it by Tim.

Also you can have one ignitor per coil, or a single four channel ignitor, it just depends on the design of the ignitor itself.

[timbosaurus]

timbosaurus
it sounds very complicated , i'm not very good at this thing & needs diagram that very simple , so i can understand it

Sorry mate, i was trying to have several conversations here

But there are 2 pics up above which may work... try hen's, if it doesn't work, try mine. Some ppl may have suggestions of which one will work in ur application. What tacho are you using?

[LeeRoy]

Yeh nah i just realised that. I guess what you need is a thing that for every 1 spark it sends out 2 or however many you need.

As for ignitors, my corolla only runs one ignitor, and my friends starlet which runs an autronic and 4 ls1 coils only runs one ignitor as well.

- LeeRoy

[rx3ip]

timbosaurus - i will try your way first , i think it makes sense but if it doesn't work , i will try hen's ...

[rx3ip]

i will ask other guys at the IPRA car meeting tonite as well ...

[timbosaurus]

Yeah, just Hen says he's tried his and it works... so i trust him more

Good luck wit it!

What car u run in IPRA?

[rx3ip]

until the last race i run the ae82 , now the ke35 is being tested before i race it

[off-road]

Is it possible to split the motec output and run 2 tachos in parallel?

[ViPeR_NiPPleX]

timbosoarus - in your diagram, are your diodes around the wrong way?

[AndyTTR]

depends on which motec. If its only a shift-light then i'd assume its just putting out an analogue (on/off) output. I'm yet to get the tacho output on the M400 to work with one of the older style tachos mentioned earlier in the thread.

[timbosaurus]

timbosoarus - in your diagram, are your diodes around the wrong way?

That are different direction to Hen, yeah, but that is cos they are for a different style of tacho.

[takai]

Yeah, the one you want is Hens. Tims is designed for an integral points style system im pretty sure.
I will be running that same style of system in my IPRA car, as the Haltech tacho output does some strange things.