People keep telling me that there's far too much information on the internet about MegaSquirt products and its all too confusing or just too much to take in. I have to agree, despite my website being crammed full of info, there's not enough specific to what's needed to get running and too much on products, versions, boards, etc, etc. So I hope this page will help some people cut through it all a little easier. I've also got a glossary of terms HERE for people who are not familiar with EFI, etc.

The following is all strictly my opinion and other people may have different views:

It is easiest to think of the ECU as two items, first the MS1 or MS2 (which is the processor thats used) and second the board, which is what the processor is plugged into.

First a little history (sorry, I know it's boring but it does help with how we got here).
Bruce and Al (thats B+G, the 2 people who own MegaSquirt) produced the first real MegaSquirt around 2002 time. This is known as MS1 and this microprocessor could be run on a PCB called the V2.2, also produced by B+G.
Then James and I got involved and we came up with the MS1-Extra code, this took us a few years to develop up to the current and last code which is version 029y4. This could be run on an MS1 microprocessor with a V2.2 board, then in 2005 the V3.0 board was produced, which again could run the MS1-Extra code on it with the MS1 microprocessor. It can also be run on the V3.57 board, but more on the boards later. The big advantage for using the MS1-Extra code over the original B+G code for MS1, was that it gave you 12x12 tuning tables for fuel, 8x8 for ignition and up to 6 spark outputs (so anything up to a V12 could be controlled with ignition and fuel!!) where as the standard MS1 with the B+G code had an 8x8 fuel table and no ignition. Another major step forward was wheel decoding, this means it can read standard pulses from lots of different engines, e.g. the Ford 36-1, Bosch 60-2, etc. The Extra code also gave you things like launch control, rev limiters, boost control, PWM idle control, knock control, etc, etc , etc! None of this was possible with the MS1 basic code, so if you go for an MS1 then it has to have the MS1-Extra code running it if you want your car to work. This is easy to do and costs nothing. It is my opinion that you should ignore the other code and just put Extra in it from the start, this way you should be running quicker. I've never sold an ECU that needed the original code in it, all have been sold with MS-Extra, all my Help files are setup for MS-Extra and all my ECU's are loaded and configured ready for your engine with MS-Extra.

Anyhow, back to the history lesson. A few years later MS2 was brought out by Bruce and Al, basically this was a daughter board that replaced the MS1 processor on the V2.2, V3.0 or V3.57 board. This daughter board has CAN capability, a faster processor, more memory and the ability to drive a stepper motor idle vavle. Despite this the MS1 processor using the MS1-Extra code was still the most popularbECU as it could run far more engines than MS2 could, mainly due to MS2 (B+G) only being able to control one (may have been two, I can't remember) spark output(s). So people still tended to go for an MS1, with MS1-Extra code. The MS1-Extra code had now got as far as it could, (version 029y4), so I concentrated on writting the MS1-Extra Manuals, making it easier for people to use and run the code, whilst James teamed up with Ken and started to put the Extra features from MS1-Extra into the base MS2 code from B+G. This code is known as MS2-Extra and slowly it has become more popular. It has more features than MS1-Extra and can decode a lot more standard crank/cam wheels. Again, it is my opinion that all MS2's should just start with the MS2-Extra code, as you will be up and running quicker. Just like my MS1 ECU's, all my MS2 ECU's come with MS2-Extra loaded into them and all my Help pages are for the Extra code.

So what about all the boards, V2.2, V3.0, V3.57, then there's MicroSquirt's, PnP and all sorts of other things:
V2.2 is really obsolete now, it can't do ignition control easily (EDIS is OK), it has no VR conditioner on it, so running 36-1 or 60-2, etc, isn't possible without adding a board to it. These are fine for EDIS based setups where no inputs or outputs are needed for knock, boost, tacho, etc. It also can't control low impedance injectors without another board being added to it and it doesn't have such a high noise immune power circuit like the V3.0 board does. There is, however, a built in MAP sensor that can cope with up to 21psi as standard or can be upgraded to 38psi, but this i the same as a V3.0 board. I just wouldn't bother with them as you will soon out grow it and want more. Reselling them is also hard as most people want more from an ECU than these can give, so prices do seem to be low for these.

V3.57, this is a copy of the V3.0 but using surface mounted components, but it is a nightmare to add things to as it has no area for soldering components needed for items like launch control, tacho, knock, etc, unlike the V3.0. There is a built in MAP sensor that can cope with up to 21psi as standard or can be upgraded to 38psi. The components are very small, so soldering wires onto them is also very tricky to say the least, so why bother, when the V3.0 is such a good board and easily fixed if it all goes wrong! After all, the V3.57 is simply a copy of the V3.0 with some stuff missing.

MicroSquirt's, these all run MS2, it can't use an MS1 or an MS3 processor (so can run MS2-Extra). Again they are limited to what you can do to them, they do have 2 VR inputs, which is handy for a cam signal, but then they only have 2 spark outputs, so the second input (cam input) can't really be used for sequential spark with only 2 drivers. They can't run low-impedance injectors or an Idle valve and it can't run an MS3. If you want to use any high powered outputs like tacho, idle, boost control, cooling fan, you'll need to add boards to it, making it bigger. It also has no built in MAP sensor, so you can't run Speed Density without adding a MAP sensor, which means you can only run Alpha_N. It's my opinion that these are best suited for motorbikes where space is limited or as the PnP stuff where they are added into a bigger box and additional boards are connected to make them more capable, but then you may as well have used a V3.0 in the first place. (The MicroSquirt is very small, a standard MS1 or MS2 ECU is 180x105x45mm, a MicroSquirt is xxxxxxxx).

V3.0 It is my opinion that the V3.0 board is still the main board to use, it is easy to fix if it goes wrong (which is rare) it has a built in VR conditioner so can be used with 36-1, 60-2, etc, it can easily be modified to run 1, 2, 3, 4, 5, 6, or more spark outputs. It can drive high or low impedance injectors, it is compatable with MS1-Extra, MS2-Extra and MS3. It has an area for adding components for extra's like tacho, launch, knock, etc and the MS-Extra manuals are written around it. There is a built in MAP sensor that can cope with up to 21psi as standard or can be upgraded to 38psi. It's also the only board I've used since 2005 in my MS1 and MS2 ECU's.

PnP is a different and new breed for the MS world, in that it simply plugs into your existing setup. There are only a few connectors available right now, so it's not for everyone. These are built around a MicroSquirt (uS) running the MS2-Extra code, the reason is that the box contains the uS and an additional board with all the outputs and inputs built in them for the extra functions needed, like tacho, launch, boost, etc. For PnP ECU's see HERE

So there you have it, in my opinion you need an MS-Extra ECU with a V3.0 PCB or a PnP ECU if your setup is one that we have an available connector for.

So now you know you need an MS-Extra ECU with a V3.0 PCB, all you have to do is decide what MegaSquirt version you need?