Custom MegaSquirt DIY EFI Conversion on a Ford 302 Windsor V8
Written By: BottleFed70

Part 1 – Parts and Equipment Used
Part 2 – Fuel System
Part 3 – EFI Sensors and Hardware
Part 4 – Assembling the MegaSquirt and Wiring
Part 5 – Tuning
Part 6 – Ignition Control and Tuning

This document is being created to follow the Megasquirt EFI conversion on my 1970 Ford Mustang Grande with 351W engine. I hope to take pictures of all the major steps along the way as well as to document time and money invested. There are various different ways to install EFI on a classic mustang. Goals, budget, and technical ability dictate which way you should do it. I settled on using the MegaSquirt ECU for a variety of reasons which will be explained later in this document. Goals:

  1. EFI on the mustang!!
  2. Keep stock classic carbed appearance as much as possible.
  3. Increase HP and Fuel mileage.
  4. Keep costs down.
  5. Install a tuneable system.

General MegaSquirt Info Webpages:

The megasquirt ECU was built on a neat concept. It was 1st designed by a couple of guys who were big into DIY (Do It Yourself). They also happened to be extremely smart. In a nutshell what they did was get together and designed a fully programmable ECU for fuel injection. They designed it in such a manner as that it was so programmable it could work on just about any engine type with any multitude of fuel injection components. It’ll work on anything from a 1cyln 2-stroke dirt bike engine to a 16cyln duel fuel aircraft engine, and anything in-between. And the really neat thing is that you don’t have to use any specific hardware, instead you program the ECU to work with the hardware you have.

So anyways, these guys design this super flexible, super tunable ECU…but then do they patent it and sell it for $5000? Nope… the release it all for free. Schematic diagrams, component layouts, even the source code is all open source. The only thing they sell you is the Printed circuit board…and it’s CHEAP! They can’t be making more than $10 on each sale. They provide a list of components and instructions. You order all of the electronic parts from wherever you’d like. Or there are companies out there that will sell you a kit with all the parts you need, or even a fully assembled ECU.

The megasquirt ECU will do just about anything you could want/imagine from a fuel injection kit EFI computer. But it’s the open source nature of this ECU that turns it from an excellent ECU to an absolutely amazing ECU. Because it’s all open source, other smart people have taken the ECU and programming, and tweaked it to be even better! There is published code out there that allows you to use the ECU for MORE than what it was ever intended for, which is exactly what the designers intended. For example: You can download code and instructions on how to modify the ECU to do additional things like nitrous control, cooling fan control, launch control, shift/transbrake control, and just about anything you could imagine. I plan on using some of these extra features in my conversion.

The Megasquirt ECU is a speed density style system. Meaning that it measures engine vacum to determine how much fuel to inject. Speed density is an excellent system, it’s only downfall is that it needs to be re-programmed in the event of a significant engine modification. Luckily this is an easy task with the Megasquirt ECU fuel injection kit and only costs you a couple of hours of tuning time with a laptop. Mass air style systems are much more forgiving to engine modifications, BUT the sensors used to measure airflow can be very expensive…and have the side effect of slightly restricting airflow and thus costing a few HP.

However, the Megasquirt ECU isn’t perfect yet. There are a few things it doesn’t do/support. The good news is that they are already working on a new version that will support everything.

  • It doesn’t do sequential injection. Batch/Bank injection only. The MS only has 2 injector drivers. So it can only control 2 sets of injectors. You can still install 1 injector for each cyln, but you’ll fire them all at the same time. This actually isn’t a big deal. With sequential injection, the injectors are often open for as much as 80% of the time anyway. Meaning that most of the time it’s injecting while the intake valve is closed anyway. Sequential injection is only beneficial at low RPM/low throttle conditions and for emissions. It doesn’t produce more power. Technically sequential injection allows you to individually tune each cyln, but to do that you’d need to install an O2 sensor for each cyln. So it’s not practical anyway.
  • It doesn’t support sequential ignition or COP (Coil over plug) ignition systems. You can still do distributorless ignition using EDIS or something similar, but not COP.

  • Part 1 – Parts and Equipment Used