Megasquirt EDIS FIAT Tach input?

[burgandy81]

Calling MS/FIAT gurus,

In the late stages of wiring up my Megasquirt in an 81 Spider. Spring is rapidly approaching!

The FI wiring harness has been removed. An RS Autosports universal wiring harness is installed with a home made relay board. While i haven't tried to start it yet, all seems to be going well.

My question. How do i get a signal back to the original FIAT tach?

My best guess is as follows;

1. The brown wire with white stripe that was connected to my original coil is the factory tachometer input.
2. Pin 2 on the EDIS control module is a diagnostic RPM signal to Ford factory ECU.
3. If I connect pin 2 from the EDIS control module to the brown/white FIAT tach signal wire will the tach work correctly?

Have I missed something?

Thanks,

Jordan

[So Cal Mark]

probably won't work, most edis systems put out a square wave for the tach. And as you will learn, Veglia was one of the few tach mfgs in the world that uses a pulse signal.

[burgandy81]

Thanks Mark!

Any thoughts on how to generate a pulse signal from the EDIS square wave? I must admit I am not really clear on the difference......

A little more homework has produced the note below from the MS manual;


"If your tachometer was previously driven by a single coil, and the IDM signal doesn't work, your tachometer will need input from two coils to indicate properly. The trick is that you need to tie all the coils together, without allowing them to ground each other. Below is a simple circuit (with Digi-Key part numbers) showing how to interface the EDIS system with your tach:"





My reading of the above indicates how to find the correct value of signals but does not discuss the nature of the signal.

All input much appreciated.

Cheers,

Jordan

[SpiderJim]

Thanks Mark!

Any thoughts on how to generate a pulse signal from the EDIS square wave? I must admit I am not really clear on the difference......

A little more homework has produced the note below from the MS manual;


"If your tachometer was previously driven by a single coil, and the IDM signal doesn't work, your tachometer will need input from two coils to indicate properly. The trick is that you need to tie all the coils together, without allowing them to ground each other. Below is a simple circuit (with Digi-Key part numbers) showing how to interface the EDIS system with your tach:"




My reading of the above indicates how to find the correct value of signals but does not discuss the nature of the signal.

All input much appreciated.

Cheers,

Jordan

Been a long time but I think a mono-stable multi-vibrator may do the trick. Frys or Radio shack should sell them for a few cents. It can be configured to pulse based on an input triggered edge of the square wave. Use a Cmos type not TTL so that you can use the battery 12 volts. TTL uses +5 volts. Any electronics tech/engineer can rig one up in a few minutes.

[manoa matt]

Jordan,

Search the forum for EDIS or "Racydave" Dave has the EDIS setup and is using a stock tach, he may provide some insight.

[burgandy81]

Hey Matt,

Thanks for the lead. I searched "EDIS Racydave" and found some good threads on the EDIS set up although nothing specific to generating a signal for the FIAT Tach.

Do you remember something specific?

Cheers,

jordan

[manoa matt]

Jordan,

Dave said its a straight hook up. This should help. http://www.autosportlabs.net/MJLJ_V4_ve ... achometers.

Here is the main website: http://www.autosportlabs.net/Main_Page

If you still have trouble send him a PM.