Atomic EFI question; RPM signal supply?

[Bundy]

I'm finishing up my atomic EFI and there is one wire left to hookup that says it is required (without timing using the timing control feature).

The instructions state "This is the tach input wire for the EFI. It connects to the tach output
of an MSD Ignition Control or Ready-to-Run distributor to supply
an RPM signal. Note: This wire is not used when the magnetic
pickup wire is being used for ignition timing."

The thing is I don't have an ignition control box and my dizzy is a Mallory Unilite breakerless with three wires; green, red, and ground so do I use one of those to supply RPM singnal? I thought my tach gets the signal from the coil?


page 8 http://www.atomicefi.com/uploadedFiles/AtomicEFIcom/2900.pdf

 

[DirtDonk]

...I thought my tach gets the signal from the coil?

It probably does. And the coil gets it's signal from the distributor.
So, wherever your tach and coil are getting their signals, "MIGHT" be able to trigger your White wire for the computer to get it's tach signal.

IF THAT'S A COMPATIBLE CIRCUIT.
I'm not sure I'm clear on their wording. And I'm not sure whether or not hooking up the EFI wire to the coil would cause any trouble. Or whether it's even a square-wave signal being generated by the Mallory distributor.
If you look back up on page 1, there is a special note that says:
"Note: The Atomic EFI requires an isolated 12 volt square wave signal to trigger the injection. An MSD Ready-to-Run Distributor (with tach output lead) or a CD ignition such as an MSD 6 Series Ignition Control."

The key words here are "isolated" and "square-wave" which, in my mind, the coil wire would not be.
To be sure, you should probably call MSD about it, unless someone here has done it recently and knows for sure.

Paul

 

[DirtDonk]

You may just have to fork over for an ignition control box after all or special distributor.

Paul

 

[broncnaz]

Does your unilite dizzy use a magnectic pickup? I think your probably going to have to call MSD and they will most likely tell you to buy there igintion. but still it may be worth calling them as they should be able to tell you something to at least get you running. Overall the best option is to have the EFI setup control the timing but you should be able to get it running without the computer controlling the igintion.

 

[DirtDonk]

There might even be a stand-alone tach-signal driver that's offered by Mallory or MSD for instances where the tach signal from the distributor is incompatible.

Paul

 

[Bundy]

I got it running by putting the white wire to the negative terminal on the coil per what I read on their support forum. it seems to idle well and blip well but something isn't right under load. I am trying to get the Idle Air Control numbers to where they should be at idle.

I'll update about my electric carb later ;D

 

[73stallion]

what did that setup run you ryan?

 

[Bundy]

The distributor uses the photo-optic triggering system and not the magnetic pickup. I'm not even sure what a 12 volt square signal is and internet research turned up squat. I had just assumed my distributor qualified as ready-to-run.

Ben, I have a buddy who knows a guy and they got me the kit at almost half off list price so I gave it a go.