Considerations you have to take into account before you order an ECU kit:

If you chose to go the do it yourself route you will have to do quite a bit of reading and learning before you even buy a DIY kit if you haven't built one before. If you really don't like to or don't have the skill to solder small parts on a circuit board then you might want to enlist the help of a friend etc to build the kit for you. It you are building your first ECU expect to take several days of building and testing of the unit to check your workmanship.

I choose to use the Megasquirt  ECU. The Megasquirt DIY kit has been on the market for many years now and has an established reputation. The kits are used on many automotive and motorcycle world speed and racing vehicles.  So they do work!

http://www.diyautotune.com/index.html

The stock number of the unit I bought is MS230-K. I also bought a "stimulator" kit (MSStim22-K) at the same time. For those of you who would rather not assemble your own unit they also have assembled units, bare PCBs, and various other parts to build/modify the ECUs etc.  These model numbers may have been discontinued by now but I'm sure they have one to meet your needs.  Again, I don't work for this company either. (I'm retired.)

If you are interested in the Megasquirt kit, I would strongly suggest that you go to their website and try to absorb as much information as you can. As they present on the site, this whole process is also meant to be a learning experience.

http://www.diyautotune.com/support.htm

The Megasquirt website has the manuals for all the ECU kits they offer and are required reading to learn what, why and how the units work. Go to the forums and read the questions/answers that other people have posted.

There is so much to learn that it will take some time to get enough information to even figure out what questions to ask. I spent several -months- reading and downloading articles etc so I could understand what & how the ECU works and what options are available.

The old saying, "The more you know, the more you know that you don't know enough." applies here.  The owners of  diyautotune and the software authors are extremely knowledgeable and are very willing to share their knowledge.

The build instructions are on line for downloading. If you are familiar with electronics you will find that the instructions are complete although they might be cryptic for a beginner. If you understand how to read electrical schematics you will find them on the site also. If you have built an electronic kit(s) before you shouldn't have much trouble putting the ECU together.

I would highly recommend that you also buy one of the "stimulator" kits when you place your ECU order. A stimulator by any other name would be a simulator. This piece of test instrument simulates the signals that you would get from the sensors on your engine. If you buy a stimulator, build it first as you need it to test the ECU as you assembled it.

You build one circuit at a time on the ECU board and then test it. If you find a problem as you go you know exactly which circuit has the problem vs building the whole ECU and then trying to figure out which circuit is not working correctly.

I could have easily built a stimulator from the schematics and using parts I already have but I decided that it would be time better spent building the ECU itself. And if you aren't that good at soldering, building the simple simulator will be good practice.

The stimulator I bought only supplies the crank sensor signal to the ECU. My engine has an 8 tooth crank "wheel" and a camshaft sensor signal that is required by the ECU. I designed a simple divide by 16 circuit to simulate the camshaft signal. (16 teeth of the crank wheel pass by the crank sensor to one pulse from the cam sensor.) My divider is powered by the simulator. There is a newer stimulator that has circuitry to simulate various common car engines timing "wheels". I'm not sure if it also provides a cam signal or not.

Near the end of building the ECU you have to load the firmware into the micro-processor on the ECU board. You use a COM port on your computer to do this. There are several current versions of the free firmware available. The basic version is very complete and can control both the fuel and ignition of your engine. There is another version of the firmware called "Extra" that has even more options that you can use.

There are also two different (free) tuning programs on the site that you use to set the ECU up for your engine. Only one program is required and they are both quite similar to each other. But at least you have a choice to see which one you like best.

Just getting the engine to start is going to be your first big test. And by using the simulator and using one of the tuning programs to set up the ECU with your engine parameters you will have a pretty good chance that the engine will start and run. The idea is to eliminate as many variables as possible before you install the ECU into the car/motorcycle etc. Considering that you have to modify the injector and/or ignition wiring of the vehicle, it's best to have all the settings that the Megasquirt is capable of already set up and or the proper jumpers installed..

OK, let's take a look at the kits themselves.

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These are all the parts that you need to build the stimulator. This kit is not difficult at all. Everything is included except the solder. The diyautotune website has a short tutorial on soldering if you need some guidance.

Here is the stimulator that I built. The various potentiometers are used to vary the signals to the ECU that simulate your car sensors. The large connector, a DB-37 [more properly named a DC-37] on the left side plugs into the mating connector on the ECU for testing. The power supply connections are located at the upper right corner.