MegaSquirt EFI – the original, and still the best
This covers the “core” MegaSquirt lineup – for other products, including MSPNP and MSPNP Pro plug and play options as well as the MS3Pro lineup, please see our “Which MegaSquirt is right for you?” page.
The original MegaSquirt-I is out of production – the processor is no longer available. Current production includes the MegaSquirt-II and MegaSquirt-III.
MegaSquirt ECU Choices
MegaSquirt-II PCBv3.0 – This is an affordable and feature packed unit set up for two channels of bank to bank fueling. Can be modified for up to six spark outputs. No upgrade needed for low-z injectors. Kit is $324.
MegaSquirt-II PCBv3.57 – A machine assembled version of the MS2 V3.0. This one adds PWM idle control as standard equipment (it requires a mod on the V3.0) and a DB15 connector for adding MS2/Extra upgrades. Two fuel output channels and can be customized for up to six ignition outputs. No upgrade needed for low-z injectors. These only come in assembled form. Assembled units are $515.
MegaSquirt-III PCBv3.0 – The MS3 steps it up and adds an even more powerful processor that also adds onboard SD card logging and USB communication. But perhaps its biggest draw is the MS3X expansion board, which you can add for eight channel sequential fuel and eight channel ignition control, plus tach output, boost control output, nitrous control, and more. Kit is $445. MS3X expansion board is $110.49.
MegaSquirt-III PCBv3.57 – A surface-mount machine assembled MS3 system with onboard SD card logging and USB communication. The optional MS3X expansion board adds for eight channel sequential fuel and eight channel ignition control, plus tach output, boost control output, nitrous control, and more. Assembled units are $645 without expansion board, $762 with expansion board.
Must Haves
JimStim – This isn’t 100% required but it should be in our opinion, let’s say 98% if you’re building the ECU yourself, and 80% required (or recommended) if you’re buying a pre-assembled ECU. During kit assembly there are several sections that you complete one at a time and test the unit after each section. You will need the JimStim to be able to test the unit. After assembly, or if you buy a pre-assembled ECU, the JimStim will help you to get familiar with the MegaSquirt and the tuning software before ever attempting to install the ECU on your engine. This is also an excellent tool for testing your Megasquirt ECU while you are working through building your wiring harness. If you have a problem and don’t know if it’s in your wiring of the ECU you can use the JimStim to figure that out, and if the worst happens and you see sparks fly, you can plug the ECU into the JimStim and make sure it ECU is still working properly so you know you can continue.
While not an required tool, it is highly recommended- we’ve seen many people come back for one with their project stalled in the meantime, and we’ve never had anyone regret buying one. If you don’t purchase a JimStim for yourself, you should at least make sure you know someone who has one that you can borrow when (not if) needed. We’ve never had anyone regret buying one, we’ve had plenty of people regret NOT buying a JimStim, and then place a second order for it. Kits are $80, assembled JimStims are $120. We also carry a power supply for it for $17 that will save you from killing 9v batteries ;).
Tuning Cable – You’ll need this to connect your laptop/PC to your ECU. It’s a standard DB9 Straight-thru serial cable, meaning pin1 goes to pin1, 2 to 2, 3 to 3, etc. If you already have one great! If not I have them for $5.50. You can find it in the ‘Tuning Cables’ section of the catalog.
Optional
USB-Serial Adapter – If you’re laptop has a real DB9 serial port, then you don’t need this. If not then you probably do. Many USB-Serial adapters are very troublesome when used with the MegaSquirt and TunerStudio. We tested a couple to find one that works reliably every time. This is it, and it’s priced at $28.99. You can find it in the ‘Tuning Cables’ section of the catalog.
Relay Board and Cable – Though the Relay/Power Board is not required, it is a convenience and reduces the chance of miswiring during the installation. The relay board provides a central place for all of the required relays, fuse protection, and external wiring for the MegaSquirt ECU. If you are installing MegaSquirt in a previously fuel injected engine you may be able to reuse all of your existing relays. If you are fuel injecting a previously carbureted engine you will need to install relays for the main ECU power, Fuel Pump, and FIdle circuit. You can do this manually or you can use the Relay Board to simplify this process. You can also build the cable yourself with the included DB37 and hood that included (one w/ the relay board, one with the ECU kit), or as the cable is kind of a pain to build I’ve made them available pre-assembled as well. Assembled, $130. 4′ Relay Cable, $89. Note that the relay cable and the wiring harness are mutually exclusive- they are not designed to be used together as once you use a relay cable you just need to run all wiring back to the screw terminals on the relay board, not a DB37 connector like the harness uses. I have had customers buy both just to harvest the labeled/color coded automotive grade wiring after cutting the DB37 off.
Lead Bending Tool – Makes life a little easier when building out the kits as it allows you to precisely bend the leads to fit properly into the PCB. My kit labels are marked with the proper spacing for each component eliminating guesswork. $5.50 You can find it in the ‘Tools’ section of the catalog.
Wideband o2 Sensor/Controller – Highly useful for tuning as this will display your exact air/fuel ratio accurately so you can tune appropriately. Narrowband o2 sensors (OE on most cars) are ONLY accurate at 14.7:1 so they are nearly useless for tuning, wideband gauges are accurate from 10:1-20:1. I have units with and without gauges. The LC-2 is an affordable unit at $166 that is suitable for permanent in-car installation. You can also buy an LC-2 with a gauge, or an MTX series which combines the control unit and gauge in a single package. The LM-2 at $280 has a built in display and can be used for permanent installation in a vehicle but it’s better suited to someone who plans to tune multiple cars and wants a system designed to be moved from car to car. The LM-2 also has the ability to read two wideband sensors and data log information from an OBD-II diagnostic port on most ’96 and later cars. Both the LC-2 and the LM-2 have dual programmable analog outputs. You can use one to drive a gauge, and the other to feed the ECU, or just use one or the other. It will also simulate narrowband to fool the stock ECU and prevent CEL (check engine lights). You can also buy Innovate gauges on their own if you already have an LC-2. You can find these in the WideBand o2 Systems section of our catalog.
Trigger Wheels
Megasquirt works with many distributors and crankshaft position sensors. But if you happen to have a trigger wheel that is not compatible, or if you want to use features your original trigger wheels do not support, you can use our line of 36-1 trigger wheels for a highly accurate crank trigger setup.
Crankshaft Position Sensors
(can also be used as camshaft position sensors) We carry a couple of different Hall Sensors that differ by how they mount, that make reading one of our custom trigger wheels a breeze, pretty much any other toothed wheel you may be using for cam or crank signal, or wheelspeed, you name it! They just work, like it should be. We carry two options:
Wiring Harnesses
We carry 8′ wiring harnesses for $83 that are designed to be adapted to any engine. They are very nice and fully labeled (printed labeling on the wires) with split loom covering. All wiring is automotive grade and the connector hood is metal. MS3 units with MS3Xpander will need a second wiring harness; we carry a ready made one priced at $86 for a 8 length. Closed element IAT/CLT sensors are $18.99 with a 6″ wiring pigtail and Open Element IAT sensors (for turbo/SC apps) are $22.49 with the 6″ pigtail. We also carry Bosch Fuel Injector connectors for several styles of injector. Megasquirts have a built in MAP sensor, while the Microsquirt can use a GM 3 bar MAP sensor priced at $67. The connector on the GM sensor is sold separately for $12.49 with a 6″ pigtail.
You can usually reuse your stock CLT sensor, and often the IAT sensor IF it’s still there when you remove the MAF/AFM. If it’s a part of the MAF/AFM then you’ll be removing that, and you’ll want to wire in a new one. Here are a few options!
- GM Closed Element CLT/Oil Sensor with Pigtail
- GM Closed Element CLT/Oil Sensor with Connector
- GM Open element IAT Sensor with Pigtail
- GM Open Element IAT Sensor with Connector
Also note that the relay cable and the wiring harness are mutually exclusive- they are not designed to be used together as once you use a relay cable you just need to run all wiring back to the screw terminals on the relay board, not a DB37 connector like the harness uses. I have had customers buy both just to harvest the labeled/color coded automotive grade wiring after cutting the DB37 off.
