Aftermarket Tach Install
 

I picked up an aftermarket tach.

I did some searching, and some independent research.

And I have one question. I run the signal wire to the negative side of the coil. In a piston car this is simple enough.
In a rotary car, do I go to the lead coil or one of the trailing coils?
The stock tach is wired to the trailing coils, but if I wire this one there it reads half down in 4cyl mode.
If I wire it to the lead coil in 4cyl will it work?
Or if I wire it to the trail coil in 8cyl?

Don't start the ricer dialogue. I'm not asking you for aesthetics. It's not your car, so don't worry about how stupid it looks.

Thanks in advance. :)

You're lucky this is very easy to do on an FC...

There is a "test" lead with a female bullet end.
Both the leading coil and the trailing coil pack have them.
If you use the leading coil end, set tach to 4-cylinder.
If you use the trailing coil pack end, set tach to 8-cylinder.


-Ted

If you have a legitimate reason for wanting an aftermarket tach you probably won't get hassled. If you don't, you probably will. So what's wrong with the stock tach?

And I'm pretty sure if you connect to the trailing coil pack (which is more convenient) you still set it to 4-cyl.

Testing if you have the right setting on the tach should be easy enough if you just temporarily hook up the tach and compare it with the stock one while running.

I would think you would need to set it as a 6 cylinder.... the leading coil fires 6 times for one rotation of the E-shaft, does it not?

No, each rotor is fired once per engine rev, so a 2-rotor fires twice per engine rev the same as a 4-cyl.

Dude...if you got no clue how a 6-cylinder and the 2-rotor 13B fires, don't open your mouth.

The 13B fires 3 times per rotation of the rotor.
A rotor rotates once per 3 rotations of the eccentric shaft.

A typical V6 fires 3 times per 2 rotations of the crankshaft in wastespark or 6 times per 2 rotations of the crankshaft in direct fire / no wastespark, so your claim is wrong either way.


-Ted

Ted: Is that the black bullet sticking off to the side of the lead coil?

Thanks for the answers so far guys.
NZ, someone gave me a tach... so I figured, why the hell not?
There isn't a real reason for it.
Why do people buy green cars? I don't know. I don't ask. :)

Yes. The trailing coil has one too, which means you don't have to run a wire the length of the engine bay.

I can thing of several reasons, but I guess you want to hear them... ;)

I bought my green car because it was the best FC I'd seen after looking at a bunch of shit ones. :)