Ford EDIS Megasquirt Conversion

January 2010

Justin Finney provided us with a writeup on use of a DIYAutoTune MegaSquirt EMS systems, trigger wheels and installation of a Ford EDIS ignition system on a 1966 Bronco.

Why Do This Conversion

Upgrading from a distributor-based ignition system to a crank trigger with EDIS and MegaSquirt offers several advantages:

  • Bigger spark – No spark energy is lost from the rotor to the cap.

  • Precise timing – Eliminates timing drift caused by timing chain slack or distributor gear wear.

  • Full control – Tune and adjust timing curves directly from your laptop.

  • Larger spark plug gaps – More ignition energy means you can safely run wider plug gaps.

  • Proven technology – EDIS modules have powered Ford cars and trucks reliably for decades.

Parts List

Here’s what you’ll need to complete the conversion:

  • MSD or Motorcraft Coil Pack (MSD-8241 recommended)

  • EDIS-8 Module

  • VR Pickup Sensor

  • MegaSquirt ECU

  • Trigger Wheel

  • 4-bolt harmonic balancer

  • Shielded wire (single pair)

  • Aluminum stock (for brackets/mounts)

  • EDIS plug wires

  • Camshaft position sensor (from Ford Explorer 5.0, used to drive oil pump and cover distributor hole)

Engine Example

This example was performed on a 289 cubic inch small block Ford, with the following build:

  • Edelbrock Performer RPM Air-Gap Manifold

  • Holley Projection 700 CFM Throttle Body

  • MegaSquirt II with 3.57 board

  • Ported cylinder heads with hardened seats and oversized valves

  • Comp Cams roller cam conversion XR282RF-HR10 with roller rockers and triple springs

  • Hedman headers, Victor Series water pump, billet pulleys

Fuel injection makes a big difference for off-road reliability. No need to swap jets or rods for altitude changes – throttle response is immediate and consistent at any angle.

Building the Trigger Wheel & VR Mount

1. Trigger Wheel – Drill four evenly spaced mounting holes to bolt the trigger wheel to the harmonic balancer.

2. Alignment – For an EDIS-8, the missing tooth must be positioned exactly five teeth (50°) ahead of the VR sensor.

3. VR Sensor Bracket – Fabricate a simple bracket from aluminum scrap. If you have a spare timing cover, mocking up the mount is much easier.

Coil Packs & Wiring

  • Cylinder pairing (EDIS-8 firing order):

    • 1 & 6

    • 2 & 5

    • 3 & 7

    • 4 & 8

Wiring pairs must be connected correctly for proper wasted spark operation.

Installing the EDIS Module & MegaSquirt

  • Mount the EDIS module under the dash for protection.

  • Wire the VR sensor to the EDIS, then connect the EDIS output (PIP/SAW) to MegaSquirt.

  • Connect coil outputs as per the EDIS firing order.

Results

The finished system replaces the distributor with a crank trigger and coil packs. Compared to the old MSD mechanical advance distributor and 6AL, this setup offers:

  • Fully programmable timing curves via MegaSquirt.

  • Stronger spark with larger plug gaps.

  • Greater precision and stability at all RPM.

  • Expansion potential (e.g., adding an MSD DIS-4 for even more ignition energy).