Dr. Scott M. Baker


Our fuel-injected turbo engine needs a brain. For this I chose the megasquirt since it seems to have the greatest DIY following. The megasquirt is a fuel injection computer designed by Bowling and Grippo. Generally the kit is something that you build and test yourself from components. Lots (and lots!) of soldering is involved. Some design choices, such as what kind of ignition drivers and tach pickup to use, are made during the build process. There are also preassembled megasquirts available from various suppliers for an additional fee.

The particular incarnation of the hardware that I build was the Megasquirt II. It took about 2-3 evenings to assemble it, including a misadventure where I soldered a transistor in backwards (fortunately something I detected before trying to power-up or use it). It’s a rewarding experience building your own computer from components, but it’s not for those who are not proficient in soldering not only small components but also big DIP ICs. Fortunately it isn’t SMT, but that seems to be the trend that the next generation of megasquirt may follow.

During the build process you’ll also build something called the megasquirt “stimulator” which you will use to test the board. The stimulator is a sort of engine simulator, that you can simulate a throttle setting and lights will blink on and off simulating the injectors pulses. It’s very good idea to build the stimulator, and a necessity if anything goes wrong and needs diagnosis.

You’ll also need a wiring harness. The megasquirt uses a DB37 connector. That’s 37-pins, potentially 37 wires to deal with. Fortunately not all of the pins are used, and a good plenty of them are grounds. You’ll end up with somewhere in the neighborhood of 20-25 wires that need to be hooked up to this beast. These are for the various sensors as well as outputs to the injectors and ignition, and of course power for the computer itself. There’s a couple of different options here, you can buy something called the “megasquirt relay board” that has some relays and screw terminal connectors, or you can just buy a bulk wiring harness and wire up the relays yourself. The latter is both cheaper and more flexible and is what I chose. I purchased a pre-made harness from diyautotune — the harness is little more than the DB37 connector with some very long wires attached to it, but it’s much simpler than doing it yourself.

You’ll also need some relays, either as part of the “relay board” or for wiring into your own harness. The megasquirt needs to be able to turn your fuel pump on and off, etc.

The megasquirt itself is not waterproof, nor is it sand-proof. I mounted mine inside of a plastic irrigation timer box from the local hardware store. The irrigation box has a nice gasket seal and plenty of room for my relays, switches, etc.

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