We had a post with MegaSquirt links before, but almost all of them were terribly outdated. Here's a new list of links to most of the pertinent MegaSquirt information:
General MegaSquirt Resources
MegaManual - General MegaSquirt information including tuning and v2.2/v3.0 board assembly, etc. You will need this resource if you're building your own ECU, but not if you're buying a pre-built one.MS/extra Resources
MSefi.com - A forum dedicated to MegaSquirt in its standard (B&G) form running the standard (B&G) firmware. The discussions here are good for general hardware troubleshooting and tuning advice:
www.MSefi.com • Index page
MSextra.com - MegaSquirt information tailored to the MS/extra firmware and corresponding hardware modifications. All MS3 MegaSquirt ECU's are running this firmware. Furthermore, all MegaSquirt ECU's for 420A's, whether MS1, MS2 or MS3, use the MS/extra firmware. MS/extra Firmware Packages and Documentation
MegaSquirt Engine Management Systems
MSextra.com forums - Forums at the aforementioned resource.
MegaSquirt MSEXTRA and MS3EFI support forum • Index page
MS1/extra - For MS1 Processors
MS1/extra Documentation - Tuning guide for using the MS/extra firmware with the MS1 processor, as well as 420A-specific hardware modification information.
MS-Extra Manual Index
MS1/extra Firmware Packages - Download official MS1/extra firmware packages here. At the time of this writing, 029y4 is the latest and probably final release. The link immediately below is a quick link to the 420A modification information.
Index of /doc/ms1extra/Downloads
MSnS Extra Ignition Hardware Manual
MS2/extra - For MS2 Processors
MS2/extra Documentation - Tuning guide for using the MS/extra firmware with the MS2 processor, as well as 420A-specific hardware modification information. The link immediately below is a quick link to the 420A modification information.
MS2/Extra Manual Index
MS2-Extra Neon-420a Manual
MS2/extra Firmware Packages - Download official release, beta, and alpha MS2/extra firmware packages here. At the time of this writing, 3.1.1 is the latest stable release.
Index of /doc/ms2extra/files/release
Index of /doc/ms2extra/files/beta
Index of /doc/ms2extra/files/alpha
MS3 Firmware - For all MS3 Processors
MS3 Documentation - Tuning guide for the MS3 processor. Much of the MS3 and MS2/extra firmware is the similar, so refer to the previous links for more detailed tuning information.
MegaSquirt MSEXTRA Manual Index
MS3 Firmware Packages - Download official release, beta, and alpha MS3 firmware packages here. At the time of this writing, 1.0.1 is the latest stable release:
If this list is confusing or overwhelming, first analyze your situation. If you purchased a pre-built and configured MegaSquirt EMS system, the best bet for a novice, determine which processor you have; MS1, MS2, or MS3. You can ignore any of the links pertaining to assembly and hardware modification. For instance, if your ECU uses an MS2 processor, go straight to the MS2/extra documentation. The tuning guide there is all you'll need.
If you bought a pre-built ECU but it needs to be modified for the 420A, determine which processor you have; MS1, MS2, or MS3. Again, if, for instance, your ECU uses an MS2 processor, go straight to the MS2/extra documentation. That page will have all the information you'll need on modifying your ECU for the 420A and subsequently tuning it.
If you bought a kit and you're going to attempt to assemble the ECU yourself, visit the Megamanual first and learn how to build your board. From there, visit the appropriate MS/extra website and learn how to properly modify that board for the 420A and whatever processor you have. Finally, use the tuning guide on that same MS/extra website to begin tuning.
If you have any questions specifically about MegaSquirt EMS, post on the msextra.com forums first since that crowd is the most knowledgeable about your application. For questions specific to the 420A and
MegaSquirt EMS, feel free to create a thread right here in the 420A Engine Management forum on DSMtuners.com.