The MegaSquirt® family of EFI controllers (including MS-I™, MS-II™, MicroSquirt®, and the MS-II Sequencer™) is a series of experimental Do-It-Yourself universal programmable electronic fuel injection controllers for spark ignition, liquid fuelled internal combustion engines -http://www.megamanual.com/v22manual/mintro.htm

Megasquirt is similar to a ramsey electronics kit, you place your order, you get a box of parts (various electrical peices, a motherboard, and a case) you solder everything together following the instructions, but instead of a radio or a digital clock, you now have a Engine Control Module to run the fuel injection on your vehicle of choice.

something to know about megasquirt is that it is kinda like your android phone (or a linux operating system) in that it is open source. the "code" (which is all the programming that makes it tick) is open source. meaning it is available to anybody to use or modify, which is one of the reasons that there is always new upgrades and parts coming out to use with them.


Picking what you need for your application

currently there are Three main types of Megasquirt(MS) controller:
Megasquirt I - this is the original MS controller, and at 150 bucks it is also the cheapest. it controls just the most basic and necessary items for fuel injection, you will need your factory (or aftermarket) standalone ignition

Megasquirt II - has all the features of MSI, but refined fuel maps(better resolution), an ignition controller (ford disributorless ignition is popular), and some neat stuff like IAC, rev limiter, wide-band o2 sensor. 260 bucks.(unassembled)

Megasquirt III - biggest claim to fame is that it supports sequential injection rather than batch like MSI and MSII, it also has cylinder-by-cylinder tuning, staged injection (2 injectors/cylinder) a great choice if you want the ultimate! 365 bucks(unassembled)

Assembly

There are very thorough instructions onlineAssembly Guide - MegaSquirt^® V3.0 Main Board abouut what goes where on the board, including how, when,and where to test it. you will need to know how to solder, or at least be willing to learn, which is ok because you will be needing a $45 stimulator (which simulates sensor inputs) for alot of the test that need to be done during and after assembly building the stimulator is a great way to learn or practice your soldering skills
what it looks like when it arrives
[IMG][/IMG]

for a soldering iron, my usual iron didn't do so great working on a pcb (printed circuit board) so i ran to radio shack and bought a really small one (had multiple tips too) and some really small solder. you don't want to leave the iron on the board so long that stuff starts to cook.

Testing

for testing, as mentioned before, you will need the stimulator, along with a multimeter. testing is all covered in the instructions

Installation

if you are installing into a carburated vehicle, you will need to either (1) build your own harness, or (2) get a factory wiring harness to wire to the MS computer. there is also a relay board that is sold to handle bigger loads as for a vehicle that is already fuel injected, there are adaptors that can be purchased(an EECIV from DIYautotune (where i have sourced all prices) is about 70 bucks, or when you buy a kit get a DIYPNP, which )
Basic wiring diagram for a MSII
http://www.megamanual.com/ms2/v3ext_wiring.gif

another point to consider is the fuel system, if you are replacing a factory FI computer you can just use your factory fuel system. if you are converting a carbureted vehicle you will need to install a high-pressure system. most port-injection systems run at 45psi, while most throttle body systems run around 15psi.

Tuning!

the most exciting(other than when it first starts!) and the most difficult part is the tuning. using free software such as megatune (free download, give it a look!) but it starts by you entering your vehicle parameters, burning them to the MS, and then changing the generated parameters to match your vehicle. It is a huge topic on its own, and for now I am going to reccommend you visit megasquirts own tuning page: MegaSquirt - Electronic Fuel Injection Computer by Bowling and Grippo ©2010
Megatune screen


Other Cool Stuff

Megasquirt has one of the larger learning curves of all aftermarket fuel injection ECM's, but the best part about it (other than its much cheaper!) is that because of its open source design, the possibilities are endless and new products are being designed constantly. here are some that are currently offered:
-"mod kits" mostly for upgraded ignitions
-megaview- a display that you build that displays computer info, can even be used for tuning.
-boost control
-VVT control
-transmission controller
-sequencer (for sequential control)

Megaquirt Main page
www.MSefi.com • Index page

Megasquirt Product Comparison
Megasquirt Product Comparison

DIYAutoTune
DIYAutoTune.com Megasquirt Kits / Assembled Engine Management Systems, Wideband o2 Sensor Systems and tuning products

DIYPNP for EECIV
DIYPNP Ford 60 pin EEC-IV Unassembled Kit DIYAutoTune.com
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well, there you go, a quick and dirty intro to megasquirt, call it beta if you like. I fully intend to add more too it (like pictures as i build my second MS), and everybody else is welcome to as well! if you see any errors, let me know!

 

Great write-up!!!!! Thanks!!!!

Prolly a redundant ???? but...
This will allow FULL fuel control from timing to quantity?
Allowing all out fueling or stringent fuel economy?
Can any computer be used or does it still require Engine/Trans base data? The reason I ask is I have a spare 87" 4.9 5spd that I'd be willing to guinea pig for my 91 5.8.

 

yes, the megasquirt takes a signal from the ignition so it knows where in the 4 engine cycles the engine is at, the timing of when they fire according to that signal is adjustable in the tuning software

quantity is adjusted by how long the injector is held open (referred to as duty cycle) as well as being a product of fuel pressure

YES! at the same time! factory computers are set so that the mixture stays as close to stoichiometric 14.7:1 a/f ratio, however best power is found closer to 12.5:1, while best economy is found closer to 16:1.

now, a narrowband (the most common) O2 sensor can only read in a small window around that 14.7:1, outside of that small window (hence: narrow band), it can only tell the computer "too rich" or "too lean" and it switches back and forth as the computer tries to keep it spot on. a wide band o2 sensor can accurately tell the computer where the a/f ratio is, from 7:1 to about 20:1!

so using a wide band sensor you can adjust your fuel map(more on that later) so that when your cruising under part throttle/light load you a/f is running leaner, but when you mash down on the skinny pedal and the vacuum drops (which tells the computer that there is a bigger load on the engine) it will sanp to a more "performance" a/f ratio!

the megasquirt completely replaces the factory computer. you could take your old on and toss it on a shelf. only other thing to consider is that if you have an electronically controlled automatic, you will need the GPIO board to control the shifting.

i don't intend on owning another auto for a long time, so i'm kinda biased

EDIT: completely slipped my mind, but it is actually possible to leave your factory computer in place, disconnecting its fuel injection outputs, and running the megasquirt as a "piggyback" which means that your stock computer can run your tranny (and on newer vehicles with multiple computers on a CAN network, it sstill allows it to talk to other modules) but its the megasquirt that is running your fuel injection.

 

I had the chance to buy a (basically complete) EFI setup for $50 from a 5.0 Mustang a month or two ago, but passed it up because it didn't have a computer or the cab wiring.

This would have been a fun experiment..

 

Megasquirt DIYPNP "How-To" - Step-By-Step Instructions - Miata Forumz - Mazda Miata Chat

found this, figured that it was such a good write up (and his work area is so much better than mine) that I would go ahead and post a link for others to see.

on the plus side he ordered a kit that uses the ford connector it completely pertains to our trucks! however i do believe that the diypnp mostly uses a microsquirt board (the little one with all the surface mounted stuff all ready on it) while boards such as my MSII do not have this board, they have more soldering to do yourself to the board. unless you buy one already pre-assembled that is.