Tachometer connections

Has anyone figured out how to hook up a VDO tach for an engine that has been converted to Edis electronic, crank fired ignition? The VDO I have was connected to the old coil. I now just have a coil pack with spark plug wires going to the plugs. Since the modification to Edis, I have simply been running without a tach, but need to address the issue.

Chuck? You need to check with the manufacturer of the ignition system. A VDO tach uses a very basic voltage signal to read. Many of the more modern ignition systems use very low voltage signal (the term sine wave is sticking in my mind for some reason) that is often not readable by a standard VDO tachometer. It's real hit and miss, some work, some flat will not.

By contacting the manufacturer, they can usually recommend an amplifier that will work. Worst case, they can tell you why it won't work (e.g. square wave signal) and you can bring that information to a shop such as Palo Alto Speedometer or North Hollywood Speedometer, and have the tach modified to accept that signal.

First stop - call the manufacturer of the ignition.

angela

If you can't get the tach signal off of either pin 2 or 11 on the igniter to drive your tach, go to http://www.autosportlabs.net/Ford_EDIS_technical_information and look at the diagram in the Interfacing With OEM Tach section. The standard diodes connect to pin 1 and 3 on the coil's 3-pin connector (-ve coil 1, 2). You can get the parts from digikey.com, part numbers are two 1N4004DICT-ND and one 1N4746ADICT-ND. Though RadioShack or similar might still carry such things. Correct diode orientation: http://www.eleinmec.com/figures/029_02.gif (Stripe lines up with cross line).

Thanks for the replies. The Edis ignition is a wasted spark design by Ford, which is brilliant and simple. It does have a control module with a lot of wires coming out of it, and I think that one of these wires may be used as the signal generator. I have been hesitant to use this lone wire due to fears of burning up something.

As soon as I find the solution, I will post it in this thread for the future benefit of others going to Edis ignition. A search of the forums did not bring up any answers.

Justin, it makes sense to use the coil pack to send a signal to the tach, since the tach was designed to be driven in that way. The links you gave me help a lot and I will follow up on them. First, though, I will check pins 2 and 11 on the Edis control module for a pulse.

Chuck, I hope you have Megajolt as the controller too. My Megajolt/EDIS has a tach out that is wired right to the VDO tach, works just fine. If you don't have the Megajolt controller, your timing is forever fixed at 10 BTDC in limp-home mode. I amn sure Chuck knows this, but others may not. Mine has been running great for 2.5 years now. I have a v3, I am assuming you have v4 since you did it recently. Scroll down on this link and you'll see the Megajolt pinout of the plug:

http://www.autosportlabs.net/MJLJ_V4_vehicle_installation_guide

Daniel, that is real slick what has been done to MegaJolt Lite to add a tach out signal. Unfortunately, I am running Megasquirt II, V3, so will have to go with the high-voltage kickback setup. Should be easy to assemble and install. I will let everyone know as soon as I get to it. Thanks for the input.

I went with Megasquirt II, V3 a few years ago to control both fuel and ignition. The limp home ignition advance is 10 degrees BTDC, but the Edis controller provides a signal to the MS ECU that enables ignition advance according to the advance table set in MegaTune and sent to the MS ECU.