Engine Management Systems & Tools






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Understanding the MegaSquirt EMS and Making the Right Choice


MegaSquirt Tech


How DIYAutoTune Configures it's Assembled MegaSquirt ECUs


WideBand o2 / Oxygen Sensor Systems from Innovate Motorsports


Shipping & Customs





Technical Articles that should really be a part of this FAQ, but would make it too huge!

MegaSquirt Tech Article -- Will the MegaSquirt work with my stock ignition system???

MegaSquirt Tech Article -- Troubleshooting MegaSquirt Communications Issues

MegaSquirt Tech Article -- Common MegaSquirt Modifications


Click Here for more (less FAQ worthy) Tech Articles, including full how to articles for many vehicles




Understanding the MegaSquirt Engine Management System and choosing a system that is right for you:

What the heck is a MegaSquirt?

The MegaSquirt line of Engine Management Systems are Do It Yourself (DIY) systems capable of full standalone engine management a a fraction of the cost of the what the 'big dogs' charge.  They were designed with education and performance in mind, so that the do it yourselfer could learn the in's and out's of engine management and tuning, while learning a good bit about electronics in the process if you choose to build the unit yourself.  What you end up with is an incredibly performing EMS that you built yourself for ultimate bragging rights when you leave your buddies behind as a speck in your rearview mirror.  And you did this for a quarter to a tenth of the cost of a 'big name' retail standalone ECU. 

Building and installing a MegaSquirt EMS will require that you do some homework.  Some of the questions and answers below will help to guide you on where to start this and how to go about it.  You will learn a lot in the process and if you so choose you will come out of it with the knowledge to properly tune your car for the current configuration you have now, and for any future power combo you can dream up and implement.  There is no limit to what you can do or to how much power you can make with this engine management system.  We know right now of a MS user running low 10's (10.08) in a 5000lb 4x4 truck making over 1000hp and 1000lbs/torque to the wheels (turbo/nitrous) who took first place in his class at Hot Rod's Drag Week 2005 and 2006. he won a high dollar ($2400+) big-name EMS system in the 2005 contest, he quickly traded it away to stick with his trusty ole' MegaSquirt 1, which he has a total of around $200 invested in.  We've got another customer making about the same level of power now on one of these units on a Land Speed car he runs out at Bonneville.  Again with an MS1 running the MS1/Extra firmware, he holds a world record in his class at 240 mph.  (Check out Gary Hart's car out at this link).  Another customer we've been in contact with recently has a MegaSquirt 2 in his rear-engine dragster.  He's running consistent 8.8 ET's in the 1/4. 

This MegaSquirt thing is no joke.


Where do I start?

Read.  Then read some more.  If you skip this step you will be asking questions later that you could already know the answers to.  We're always glad to help though as this is a DIY based system some of the burden does fall on the user to do their homework, the big dogs charge an extra $2000+ for their systems to do some of the homework for you.  We'll help you with your homework for free, but you've got to come up with the final answer.

Start with our "Which EFI system is right for me?" link on our site here: Which EFI system is right for me?

Then read, cover to cover, the MegaManual at that same link:  (you can skim the assembly section)

Then read about what is known as the MS/Extra firmware.  This is a free firmware update for the MS1 and MS2 that greatly expands the featureset of the ECU, highly recommended.

MS1/Extra Features and Documentation

MS2/Extra Features and Documentation  (includes MS2/Extra for MicroSquirt/MicroSquirt Module, and DIYPNP usage)

MS3 Features and Documentation - (All MS3 ECUs use a single firmware branch, and it's written by the 'Extra' developers.)


Now that you've read up on things start lurking around and/or asking any remaining questions on the MegaSquirt Support Forums at (Extra forums, advanced topics) and (basic assembly guidance and support), there is so much helpful information at these two forums that it's insane.  The search feature is your friend.  Try searching for your vehicle or engine, 'RX7', or 'Subaru', or '4AGE' and then go through the threads that are returned.  There are a ton of very helpful people on these forums that will bend over backwards to make sure your project is successful, IF they can tell you've 'done your homework' and that you're not expecting them to do all of it for you.  Questions like, "My car has an optical crank sensor in the distributor with one hole for each cylinder, spaced evenly apart.  Will the MegaSquirt-II work with this signal?" will usually get very quick and helpful responses.  On the other hand, questions like "What do I need to make my 1967 Sooper Dooper Pooper Scooper scoop poop at an amazing rate of speed?" generally get ignored because it's obvious the person didn't put much effort into helping themselves and that they are hoping someone will just pour out a magical answer for them to help their Sooper Dooper Scoop Poop go faster.

Another link you might find interested-- - This site allows users like yourself to proclaim their MegaSquirt'd success to the world, often with details on exactly how they implemented the system.  It's organized by vehicle manufacturer so it's easy to find others with similar vehicles to your own.

If you don't know the right questions to ask, keep reading.  You'll get it.

You can also Contact Us and we'll do our best to assist you.  We've got three full time tech support guys on the team, ready and waiting (actually, they're not waiting, they're probably digging through a couple hundred emails right now), but they get back to you fast!  Please see the list of questions below that will help us to help you.  The more prepared you are and the more you know about your car and your ignition system the better off we'll all be and the faster we'll be able to get you up and running!



What do I need?

Another question that doesn't have a quick short answer... but the quick short answer is:  An ECU (there are a few options here of course), a stimulator (95% required), and a tuning cable.  Optionally you may need a USB-Serial Converter if your laptop doesn't have a DB9 serial port, and/or a Wideband O2 system such as the Innovate LC-1 or LM-2 (with or without a dash mount gauge) which will make tuning your Air/Fuel Ratio SO much easier and more accurate that you'll be glad you spent the couple of bills to do it.

Click Here to see a page we put together to assist people in these decisions-- It doesn't cover all of our products but it does cover some of the more commonly requested options at a high level and provides some idea of pricing (check our catalog for exact prices of each component).  For a complete product list, to validate current pricing and/or to place an order go to



How difficult is it to assemble a MegaSquirt myself?

It takes most people new to electronics assembly 6-10 hours for their first time assembly of a PCBv3 ECU, a bit less for a PCB2.2, and the stimulator (which you should do first) is very simple and takes maybe an hour to assemble for a first-timer.  I'd recommend going to and querying for 'Soldering Technique' and reading up a bit, and maybe pickup up a cheapo practice kit if you want to practice your technique a bit before starting in on the MegaSquirt.  Check out Youtube for some good solder technique videos like this one. We do often recommend you build your own MegaSquirt at least the first time around as it will familiarize you with the hardware particularly if mods are going to be required for your implementation.  This way it's not all new to you when you get to the mods needed for your setup.

Note we also offer all of our systems fully assembled if you'd prefer to skip the assembly phase.

Some relevant quotes here:

"It was high counsel that I once heard given to a young person:  Always do what you are afraid to do."
-Ralph Waldo Emerson

"Whether you think that you can, or that you can't, you are usually right"
-Henry Ford

"Can't never could do nuthin'"
-Paul Carter (my stepdad when I was growing up, whenever I'd say I can't do something)


Some relevant quotes here:

"It was high counsel that I once heard given to a young person:  Always do what you are afraid to do."
-Ralph Waldo Emerson

"Whether you think that you can, or that you can't, you are usually right"
-Henry Ford

"Can't never could do nuthin'"
-Paul Carter (my stepdad when I was growing up, whenever I'd say I can't do something)



I have a (insert year, make and model here), what exactly do I need to order for my car?

We'll be glad to help you spec a system for your car but we'll first need some information from you as we unfortunately don't have hands on experience with every car out there.  Below is a list of the questions we will generally need answers to in order to assist with this.  You can find this information in service manuals for your car/engine, on message boards and enthusiast sites, or sometimes by tearing into your ride and looking.  It will be a big help if you've followed the steps in the 'Where do I start?' section above so that you have a pretty thorough understanding of the MegaSquirt line of Engine Management Systems and you may find that you've answered your own questions by the time you've done this.  At any rate these are some of the questions you will need to ask yourself, and that we will need to know the answers to in order to be able to assist you:

(Please try and answer all questions as the two most people skip (3&4) are the most important for ignition control!)

  1. What year/make/model/engine/tranny? (Pretend your at the parts store, ordering a starter.)  If this isn't the original engine/electronics let us know that too.
  2. Are you looking to control fuel only, ignition only, or fuel and ignition? Is there anything beyond these features that you are looking to control - fans or boost, for example?
  3. Is it important to run sequential injection for this project, or is bank to bank fueling OK? (See our notes on sequential injection if you're not sure.)
  4. What are the engine details (type, number of cylinders, previously fuel injected or carb'd?)
  5. What type of ignition system does your car run? Is there a distributor?  Coil pack?  Coil on Plug?
  6. What sort of sensor(s) does it use to trigger the ignition? Variable reluctor (magnetic pickup)? Optical? Hall effect? Old fashioned mechanical breaker points? Are the sensors triggered by trigger wheels on the crankshaft / flywheel, distributor / cam, or both?
  7. How many teeth / windows / slots and are on the crank or distributor trigger wheel? How are they arranged? (Equally spaced, missing teeth gaps, etc)
  8. Does this engine have a fast idle valve (IAC)? If so, how many wires are connected to it?
  9. Rate yourself 1-5 on technical confidence in yourself.  1 being "I can't paint by numbers" and 5 being "I can probably build a car from scratch if I have the right documentation, and I'm resourceful enough to do some research and find some of my own answers."  We need to know this as some of the 'less traveled' roads will require you to make modifications that in some cases we haven't performed ourselves yet and based on this response it will help us to know whether this type of solution is for you or not.  I challenge you to 'stretch yourself' a little bit.  You won't ever learn anything (about yourself and your abilities) if you don't try to do things that you're not quite sure you can do... and then find that you can.
  10. Are you looking to build your own ECU from a kit or buy a pre-assembled ECU?
  11. Are you open to retrofitting a different ignition system such as the Ford EDIS distributorless system or one of our crank trigger kits if it is determined that the MegaSquirt will not properly (or easily) control your factory ignition system?  Many factory systems MegaSquirt can simply take control of, some it cannot.  EDIS to the rescue!  It's cheap, simple and works great!

If you can cut and paste the above list into an email and answer all questions it would be very helpful to us-- otherwise I'll just have to ask you the same questions more than likely in order to best be able to assist you.

Also-- Here is a page we maintain with links to installation documentation for various different vehicles that we've found around the web-- This is a good place to check for information that just might help you 'squirt your ride.  Even if it's not an exact match there is much to learn by looking over other's installations and notes. 

If you find or write more install docs that we can add here please let us know.



What is the difference between the MegaSquirt PCB 2.2 / PCB 3.0 / PCB 3.57?

They are all three able to use the MegaSquirt-I CPU as well as the MegaSquirt-II and MegaSquirt-III daughterboards, but they are based on different versions of the circuit board and as such there are different features .  You can click on any of the headings below to view an example of the product with pictures.


The v2.2 board dates back several years, it's the least expensive of the currently available options, and the least developed.  It's a great low budget solution that has served many people well (and continues to).



The v3.0 board has a lot of improvements made to it to reduce electrical noise and increase robustness (damage resistant), as well as make the board easier to expand.  All of the improvements with the V3.0 board are listed here.

The main high level differences are that the uprated flyback circuitry is included so you can run low or high impedance injectors, there are several improvements to make the board more robust and harder to damage in the event of a mis-wire or overload event. A prototyping area was adding to the PCB, and several changes were made to prepare the board for the MegaSquirt-II and MegaSquirt-III Daughterboards.



The v3.57 board's major claim to fame is it's 'surface mount (SMT)' design.   Otherwise it is almost identical to the v3.0 board and the above information on the v3.0 board fully applies.  The only other major differences are:

A) the addition of a PWM capable idle control transistor allowing control of a PWM idle valve or a standard on/off type FIDLE valve without need for modification.  This was a common modification applied to the v3.0 board and is no longer needed on the v3.57.

B) the addition of a DB15 connector next to the DB9.  By default this doesn't do anything, but is there to allow for extra I/O for modifications.  It takes the place of the externally viewable LEDs, which are now internally surface mounted on the PCB.

C) Several signal pads have been added making common modifications easier.

D) The prototype area was sacrificed (removed) to make all of the above possible.


In general, if you're looking for the cheapest option possible, the PCBv2.2 makes sense.  Chances are you'll mate an MS1 processor with it in this case, such as with our MegaSquirt-I kits and assembled units.  Otherwise, if the small difference in price is worth it to you to go with a tougher and more featured board that was built with expansion in mind, the v3.0 or v3.57 boards make more sense.  We offer MegaSquirt I's, II's, and III's using these two boards.  Some prefer the thru hole v3.0, and some prefer the v3.57.  See the above to decide your preference between the two.



How big is the MegaSquirt case?

The MS1 and MS2 cases are is 6.2" x 4" x 1.75" with mounting flanges on each end that are about .5" long, so total length including flanges is about 7.2".

The MS3 cases are a little taller, about 6.2" x 4" x 2.6", again with mounting flanges on each end that are about .5" long, so total length including flanges is about 7.2".




MegaSquirt Tech:


How does a MegaSquirt compare to having my car 'Chipped'?

It is possible to get many of the same performance benefits of the MegaSquirt by having your car chipped IF the tuner chipping your car has your car onsite and custom tunes the map for your specific configuration on a steady state/load bearing dyno.  If you are not the hands on type, or you don't plan to EVER modify your car/engine again, then this is not a bad option.  If you do ever mod your car again it will likely need to be re-chipped, on a dyno by a qualified tuner, to get the maximum performance out of it.  If you simply send your ECU off to a chipping company who is supposed to load a map on your car, or buy a canned tune online to load on the chip yourself you're likely not going to get the results you're after.  In either case that tune/chip was NOT designed specifically for  your car on a dyno by a qualified tuner so you are simply not going to get the maximum performance possible out of the engine.  They simply can't do it-- they have to make a lot of assumptions with no scientific testing on YOUR car. 

However, if you really want to take control of things, if you do have plans to further modify your car and you don't want to have to pay someone to rechip it every time you mod it, and if you are open to learning something in the process then by all means a standalone EMS is the way to go.  And there is no more powerful system per dollar spent than the MegaSquirt, in fact even with the affordable price out of the picture the MegaSquirt line of Engine Management Systems rival the featureset of many aftermarket 'high dollar' systems.  Particularly the newest MS3 system with MS3X Expander board.  We're talking 100% of the functionality of many high-dollar systems, without the high-dollar price tag.


Don't I need sequential injection to make big power?  Does the MegaSquirt offer this?

Sequential injection attempts to only spray fuel while the intake valve is open for the cylinder that is about to fire, which in most cases is only possible at low engine speeds between idle and low speed cruising.  It can have benefits in emissions, drivability, and fuel economy at these low engine speeds.

Batch injection (which is what the MegaSquirt-I and and most MegaSquirt-II versions do) does not attempt to spray only when the valve is open.  It's a fact that at higher engine speeds you won't have enough time to spray all fuel while the valve is open, making this somewhat pointless, particularly for a performance oriented application.  At these higher engine speeds 99% of sequential systems (exceptions being race only systems with super massive injectors) cannot spray all of the fuel needed while the valve is open anyways, and sprays it both while the valve is opened and closed, very much like a batch system such as the MegaSquirt I and II.  We've dyno tested several cars with using batch fire and sequential injection on the same motor. Peak power was the same without using individual cylinder tuning. The sequential fire setup did run a bit more smoothly at idle and at light throttle angles, however.

That said, the MegaSquirt III system with the MS3X Expansion board or MS3-Pro will do full 8 cylinder sequential fuel and ignition.  If you're looking for the absolute best possible emissions and fuel economy, as well as the ability to fine tune each cylinder individually, then the MS3 system is the way to go.

There is generally no significant performance difference with a sequential system over a batch system unless you use individual cylinder tuning. There can be minor emissions and fuel economy benefits at very low speeds though. If your tuning budget allows for individual cylinder tuning, it may be possible to pick up 3-4% more power depending on how much cylinder to cylinder variation your engine has.


Is the MegaSquirt Engine Management System just for making more power?  Or can I get better gas mileage out of it too?  What about emissions?

MegaSquirt Engine Management Systems are most often installed in the pursuit of power gains, but often economy gains are just a possible.  In fact due to the nature of programmable fuel injection usually you can achieve some of both, power when you are on the throttle, economy when you are lightly cruising around town.  It's really all in the tune.  The factory will have tuned your gasoline engine to run around at 14.7:1 air/fuel ratio (AFR).  This is the 'chemically correct' or 'stoicheometric' (stoich for short) air/fuel ratio (AFR) which basically means this is the air/fuel mixture at which the most complete burn of the fuel will occur.  It's also the proper mixture for the catalytic converter to best be able to do it's job, in other words, your car comes tuned from the factory for reduced emissions.  If your goal is power, you'll be tuning a somewhat 'richer' mixture than this, for a naturally aspirated car this is usually in the 12.6:1-13:1 range under throttle.  For economy you'll tune somewhat leaner than this, as lean as 16:1 possibly if your engine runs well there, or maybe even a tiny bit leaner when lightly cruising on the highway.  That can lead to quite an improvement in highway mileage over the factory 14.7:1 tune.  Not all engines like to cruise this lean so your 'mileage' may vary, our MR2 seems to love 16:1 on the highway-- We were able to get 34.5 MPG on an 1100 mile trip at an average speed of 70 MPH, a decent increase over stock for sure!  And one of the great things about EFI is you don't have to sacrifice WOT power to do this-- that MR2 that's getting better mileage than stock on the highway, also makes more power than stock when I step on it-- it's an entirely separate part of the EFI map!

That said, if tuning for emissions is your goal you actually may be able to do a better job than the factory did as well though your task will be tougher as that's at the top of the factory's priority list.  Areas you may be able to improve:  Often factory cars idle richer than 14.7:1, and under power are again richer than 14.7:1, though they likely need to be at wide-open throttle, with proper tuning there is likely room for improvement in emissions and fuel economy.


Note-- All parts are sold for OFF ROAD RACE-ONLY ground-vehicle use only. Aftermarket EFI/EMS systems are not for sale or use on pollution controlled vehicles. Alteration of emission related components constitutes tampering under the US EPA guidelines and can lead to substantial fines and penalties. Your state/district may also have specific rules restricting your tampering with your vehicle's emissions system. In short, as stated before, our official policy has to be RACE or OFFROAD USE-ONLY in ground based vehicles ONLY.

Bowling and Grippo have compiled some excellent info on legality of aftermarket components on cars here that you should check out as well.  Click here to open a new window with this info.


The MegaSquirt 1 and 2 ECUs seem to have only four injector output pins (or terminals on the relay board) but they are labeled as pairs so this is even more confusing, do I have two or four injector outputs?  And how does either two or four outputs allow me to run 6, 8, or 12 injectors?

With the MS1 and MS2, you've got two 'banks' of injectors. Or two 'groups' if you will.  You can use one or both of them. With 1-6 cylinders one is fine, though you can use both and generally would do so unless you were using the second bank for a different purpose (staged injection maybe). With more than six you should share the load across both banks. 

Each bank has two terminals that you bring together to a nice fat (like 14ga) wire that then goes out to all of the injectors on that bank. So for an 8cyl for example you might choose to run two banks of 4 injectors each. You'll run 12v to one side of all eight injectors that's hot in the 'crank' and 'run' positions. Then you'll run the 14ga wire out from one pair of terminals (one injector bank output) nearby the injectors where you'll split that 14ga off into 4 smaller gauge (20ga probably) short wire runs to the individual injectors. Do the same thing for the other bank.

The MegaManual's 'Sensors and Wiring' section has a wiring diagram that shows an example of this for a 4cyl car. Same principle for an 8cyl or even a 12cyl.   Here's a link to the wiring diagram for MS1/MS2 that was just mentioned.

Note that when running a MegaSquirt-III, you can still run batch injection if you choose, using the same wiring diagram as above.  However you can also purchase your MegaSquirt-III with the MS3X Expander Board, and then have up to 8 channels of sequential fuel and ignition outputs available.  (Not to mention all of the other features this enables, lots of I/O).

Check out the MS3X Wiring Diagram here.


Is there a central place where I can download maps that others have shared?

Maps can sometimes be found on the or forums that are similar enough to be used as a base map for your vehicle but it's generally not encouraged to just grab someone's map and run with it, as there are a few things to consider first. You want to ensure their setup is as similar to yours as possible, including the engine, ignition system, MegaSquirt version and firmware version they're running.  If they were running a different MS version, or firmware version than you then you can still copy the information from their map manually, but don't import it into your ECU as it's very possible some of the data won't import properly into a different firmware version.  This could help you get started in the right direction towards building your map.

Another thing to consider (maybe the biggest), especially if the ECU setup you're using required mods to control your vehicle's ignition system, is are the mods you're using identical to the mods used by the person that created the map?  Are they using the same ignition components (ignitors, coils, etc)?  If anything is different here their ignition settings could be different from what you need, and could damage your coil or ignitor.  Things to watch out for are the SPARK OUTPUT setting (inverted or non) and the DWELL settings. 

The most important thing to remember is that no matter how good so-and-so told you their map would work on your car, you are still ultimately responsible for making sure your ECU is properly setup for your car, and that your car is properly tuned.  That means looking over the map's settings BEFORE you start the car.  Do the ignition settings look right and does the ignition table look logical?  Is there 60 degrees of timing at WOT, if so, that's probably not right....  Then when you start the car you should still treat it like you need to tune it yourself from scratch, you've just hopefully got a good headstart.  Tune the idle first, then slow speed VE and ignition, cruise VE and ignition, and then work on up to higher loads and finally WOT VE and ignition.  Read the MegaManual cover to cover.... again....AGAIN!!!   There are good books out there on tuning as well such as the one recently published by our lead tech Matt Cramer and owner Jerry Hoffmann (Click here to check it out). 

 This stuff is fun!  But you do have to do some homework.  Best and most rewarding homework I've ever done though.


Idle Air Control valves versus Fast Idle Valves--- What does my car have and how can I tell?

Here's a way to figure it out-- on a cold morning, when you start your car up on it's stock ECU it idles higher than normal right?  That's because this valve is partially open letting more air in to idle the car up so that it warms up faster.  Now... if you sit there until it warms up, does the idle drop back down to normal all of a sudden?  If so it's a FIDLE valve (generally two wires, ground and 12v+). 

Alternately, does it slowly idle back down to normal a little at a time, gradually reducing the idle speed as the engine warms up?  If so it's either a PWM or stepper motor valve. 

To determine if it's a stepper or PWM valve, find the valve on your engine, it will be attached to the intake manifold, either directly or via a hose.  How many wires does it have?  Generally a PWM valve will have 2 wires, sometimes 3, and a stepper motor IAC will have 4 wires, sometimes 6.  The MS2/MS3 stepper circuit was designed with GM/Jeep valves in mind, however it works great on many different stepper IAC systems, including most all USDM, Euro, and Japanese vehicles that use steppers, among others.


I'm considering an EFI conversion - converting my car from carbs to EFI-- what do I need to consider?

Starting with the fuel system it will need to be converted to a high pressure system suitable for fuel injection (around 43.5 psi for MPI, less for TBI if you go that route), if you can get a TBI unit (with TPS) that bolts to your manifold that may be the simplest route (though their likely will be more power and better economy/emissions in a good MPI setup), otherwise you'll need to buy or fab up an intake manifold and throttle body with TPS, fuel rails, etc.    We don't carry intake manifolds at this time, though we do carry many of the fuel system components you will need, and of course the engine management systems and accessories.

FOR FUEL AND IGNITION CONTROL-- We'd suggest running a MegaSquirt-II, or MegaSquirt-III, using the PCB v3 or v3.57.  You'll need a compatible Crank Angle Sensor to determine engine position and RPM from as well as some way to fire the ignition -- with the MS2 this is generally a distributor based solution or the Ford EDIS or GM DIS distributorless solutions which could be adapted to your engine (most adaptations use EDIS which also uses it's own 36-1 Crank Angle wheel which can be mounted on the crank pulley).  You can read more about ignition options in the MS/Extra documentation at 

FOR FUEL ONLY-- You could run any of the MegaSquirt ECUs, the MS1, MS2, or the MS3.  We'd recommend PCB v3.0 or PCB v3.57.  Pickup up your ignition signal from the negative terminal of the coil, run your IAT, CLT, TPS, and O2 sensor inputs to the MegaSquirt, calibrate the MS to the sensors if they are not GM sensors and start tuning.

If you haven't yet we'd again suggest taking a look through the 'MegaManual' over at and/or the MS/Extra version of the manuals at as it will go into detail about most aspects of the conversion/installation/configuration/tuning and help to make things clearer. 

Here's a list of what most people would commonly pick up:  We'll list what we see as 'required' and then some 'recommmended' and 'optional' components.  Then we'll provide a link that goes into some detail on why we made these recommendations and that will also help you to decide on the optional components.



(Note you can substitute DIY kits for the below to save some cash and learn more about your EFI system, and electronics in general, in the process.)


along with:


'Highly Recommended' 

Innovate LC-1 Digital Wideband Controller with Sensor 

12' MegaSquirt Wiring Harness (MS1 / MS2 Ready)  and possibly the MS3X Harness as well if you're running the MS3X board.



MegaSquirt Relay Board - Assembled Unit 

MegaSquirt-I Relay Cable (if you're using the relay board and cable, you don't need the standard MSHarness12, see note in product description)

GM Open Element IAT Sensor with Pigtail 

GM Closed Element CLT / IAT Sensor with Pigtail

USB to Serial Adapter - Works with MegaTune! 


Here's the link I mentioned with more info on each of the above--



Where can I find the MegaSquirt Schematics?

MegaSquirt ECU PCB 2.2 Schematics   More info at

MegaSquirt ECU PCB 3.0 Schematics     More info at

MegaSquirt ECU PCB 3.57 Schematics     More info at

MegaSquirt Relay and Power Board Schematics     More info at


Using the Relay Board with the PCBv3, what do terminals S1-S5 do?

This is the best way to go about this-- You can use the schematics for the PCBv3 ECU and/or PCBv3.57 and the Relay board to trace it back. Here are the Relay Board schematics and here are the PCBv3 schematics and PCB v3.57 schematics.

Here's the quick answer though mapping these terminals back to the corresponding pin on the PCBv3 ECU's DB37:

S1 = 25
S2 = 27
S3 = 29
S4 = 31
S5 = 36

With the MS-I these were unused by default, available as spare inputs/outputs. With the MS-II and MS-III (legacy installation) S1-S4 are used for the stepper motor IAC, and S5 is the ignition output.

For more information on the Relay Board check out this page:

Note you can do the same cross reference for the PCB2.2 ECU and the Relay Board, just use the PCB2.2 Schematics.  Though the pinout is of course the same...


Will the MegaSquirt work with my stock ignition system???

This is the most important thing to determine when attempting to control both fuel and spark.  In an ideal situation, you can take control of your stock ignition system and call it a day.  That is very common on distributor based vehicles, and the variety of supported wasted spark and coil on plug ignition systems is now very large as well, particularly with the newer processor ECUs (MS2 and MS3).  For some ignition systems, particularly when used with MS1/MS2 ECUs, you may need to do a bit of modification to the MegaSquirt in the way of adding coil drivers or input circuits (tach input) and such to set it up to control some ignition systems.  Here's a good article that will help you understand the basics here:

Tech Article:  Will the MegaSquirt work with my Stock Ignition System?


Note there are MANY factory ignition systems supported, with the list growing constantly.  Check the MS/Extra docs for details.


If you do need to adapt a different ignition system to your vehicle:

Ford EDIS is a distributorless ignition system that's very easy to adapt to just about any internal combustion piston engine out there -- you just need to mount (weld or bolt) a 36-1 trigger wheel to your crank pulley and build a bracket for the VR sensor to locate it next to the trigger wheel. That's the hardest part and the only fab work. The rest is a bit of wiring. The EDIS system has an EDIS module and a coil pack. The module is wired to the VR sensor and the MegaSquirt, and also the coil pack. The MegaSquirt-II or MegaSquirt-III is what we would recommend for EDIS control and will take full control of an EDIS ignition system easily.

Here are some links with more info:

Here's all the parts that are needed and where they can be found if you wanted to dig them up yourself:

Here's the MS1/Extra EDIS documentation:   MS1/Extra EDIS manual

Here's the MS2/Extra EDIS documentation: 



Can I leave my stock ECU in place to control non-EMS related gadgetry, while letting the MegaSquirt control the engine?

Yes you can-- This is what is known as a 'Parallel Install' and on some newer cars where the OEM is putting more and more responsibility on the ECU (more than just an Engine Management role) you may need to go this route.  Some of the other responsibilities that OEM's are putting on the stock ECU are gauge control, cruise control, auto tranny lockup, etc. 

You'd basically leave the stock ECU in place, and leave the stock sensor inputs connected to it. Then you'd run a new CLT and IAT sensor for the MegaSquirt (you can share these but it can be troublesome, read up on it if you want to share IAT/CLT with the stock EMS), and then share the TPS and O2 signals between the stock ECU and the MegaSquirt. You'll disconnect the spark output(s) from the stock computer and wire the spark input to the MegaSquirt (pin24). You should be able to share that signal in most cases. Next wire the MS spark output (pin36 usually, depends on model and mods) to the stock igniter or directly to the coil if the ECU is set up for direct coil control.   Then disconnect the fuel injectors from the stock ECU and wire them to the MegaSquirt. This will basically give your factory ECU control of everything but the engine, and give the MegaSquirt control of the engine.

Note that's just a quick rundown, and not necessarily in the order you might go about things.  For example, you might prefer to start with fuel control, go ahead and do all of the above EXCEPT the spark output change (you do need the crank/cam signal input shared with the MS at this point).  This way you've got full fuel control, but the stock ECU is still controlling ignition.  You can dial in your fuel map and get the car running good, and then move spark over as well with this transition being much smaller than taking it all on at once.  Not to mention you'll know the MS ECU and the tuning software MUCH better.

Tech Article:   Installing MegaSquirt in Parallel with the Stock ECU


Note some may call this 'running the MS as a piggyback' though it's not.  A piggyback ECU simply manipulates the stock sensor signals to 'trick' the stock ECU into performing differently.  There is no trickery going on with an install as described here,  this is a full standalone EMS implementation, we're just leaving the stock ECU around to control the NON-EMS stuff.  Call it a 'Parallel Install' as the two computers are working in parallel each playing their part, with no attempt at tricking each other by manipulating inputs.  


Can I use the stock IAT and CLT sensors with the MegaSquirt?

Yes you can in almost every case-- the exception is that you sometimes remove your stock IAT sensor when you remove your MAF/AFM as it's often built into stock MAF or AFM on many cars.  If this is the case then you'll need to add another IAT sensor to the intake tube, usually just before the throttle body, and after the intercooler if you have one.  The idea is to measure the air temp as it enters the engine.  After anything heats it up (like a turbo/supercharger) and AFTER anything cools it down (intercooler, meth injection, etc).  You want the actual air temp of the air as it enters the engine.

Here's an article that shows how to measure the resistance curve of your stock (or any really) sensors so that you can input these values into your MegaSquirt EMS via the tuning software for MS2/MS3 ECUs, or via EasyTherm for the MS-I, to calibrate your ECU for your sensors.

Tech Article:  Measuring and Calibrating your Coolant (CLT) and Intake Air Temp (IAT) sensors



Help!  I broke the pins on my MS-II Daughterboard!

The pins are Digikey Part# ED7764-ND. 


How do I power cycle or reboot a MegaSquirt?

These both mean turning the MegaSquirt off and back on again. Some settings only take effect when the MegaSquirt powers up. The latest versions of MS2/Extra and MS3 firmware will display a message in TunerStudio when you change a setting that requires power cycling to take effect.

's MegaSquirt Assembled Units MS130-C and MS230-C


There are several 'optional' or 'choice required' steps during assembly of the PCBv3 MegaSquirt units, how are the DIYAutoTune ECU's configured?

MegaSquirt-I EMS's are setup by default as a fuel only EFI controller running though they are running the current stable release of the MS1/Extra firmware.  These are configured to be triggered from the (-) negative terminal of the coil by default.  It is fairly easy to convert them to be triggered from a Hall/Optical/Points trigger if you prefer.  Here are the steps to take:
  • Cut out C12 and C30.  Don't jumper them or anything, just clip the leads and leave them out.  (Assembly steps 50h and 50d)
  • Jumper D1.  You can remove the diode first, but you don't have to.  It's easier to just solder a little lead shorting both of it's legs together.

MegaSquirt-II EMS's are by default configured for fuel and ignition control running the current stable release of the MS2/Extra firmware.  These are configured to be triggered from a Hall/Optical/Points trigger by default. 

MegaSquirt-III EMS's are by default configured for fuel and ignition control running the current stable release of the MS3 firmware.  These are configured to be triggered from a Hall/Optical/Points crank trigger by default, and with the MS3X board added also support a similar Cam sensor input allowing sequential fuel injection. 




WideBand o2 / Oxygen Sensor Systems from Innovate Motorsports


Why is a wideband o2 sensor better for tuning AFR than a narrowband o2 sensor?  Isn't my 1/2/3/4/5 wire stock o2 sensor good enough?

A wideband o2 sensor system will give you far greater tuning ability than a narrowband sensor.  The problem with a narrowband sensor is that it is only truly accurate at 14.7:1 AFR.  The factory will have tuned your engine to run around at 14.7:1 air/fuel ratio (AFR) at cruise and light load conditions. This is the 'chemically correct' or 'stoicheometric' (stoich for short) AFR which basically means this is the air/fuel mixture at which the most complete burn of the fuel will occur. It's also the proper mixture for the catalytic converter to best be able to do it's job, in other words, you car comes tuned from the factory for reduced emissions and that's why that narrowband sensor is there.  Therefore it will be useful for tuning cruise Air/Fuel Ratio (AFR) only as long as you're tuning for 14.7:1 air/fuel ratio.  However under Wide Open Throttle (WOT) you'll want to tune for somewhere between 12.6:1 and 13:1 (NA) or richer for forced induction, and the narrowband won't tell you anything useful at that range.  Likewise at cruise you may not want to tune for 14.7:1, maybe you want better fuel economy at cruise and you want to tune to 15.5:1 or even a bit leaner possibly. Only a wideband can give you accurate feedback outside of the stoich 14.7:1 reading that NB sensors are designed for, and allow you to tune for best power and best economy.

In short, a wideband oxygen sensor will give you a measurement of your Air/Fuel Ratio from about 10:1 up to about 20:1 AFR allowing you to target exactly the AFR you're after at all times.  A narrowband can only tell you when it's 14.7:1, and is therefore nearly useless for tuning.


Do I have the newer or older style LC-1?  Should I get it replaced if it's older?

You can skip this section if you bought your LC-1 after June of 2006.

First...  the issue is that if there is a voltage differential or any other cause that would pull your 5v output to anything above 5v it could burn out the DAC on the older model LC-1.  Wired properly most people never had a problem with them but Innovate decided to make the circuit more robust now and provided an updated version of the product, and RMA'd any units that were damaged due to the 'issue'.  They were truly a class act in how they handled this.

The 'older model' LC-1's were up until about June 2006, in white/beige box.  The new models were sold since then and Innovate updated the packaging at about the same time to a blue/black box and later still to a white/red box.  The more definitive way is to determine which model you have is to check the serial number.  The serial for the LC-1s with the analog output fix are LC11188 forward and all LC-1s that start with CLC.  Note that in  fall 2007 Innovate started using a white/red box, these are still the new LC-1's, just using a different box design.

Bottom Line: Wiring it according to the docs is the most important thing. Not just for longevity but for accuracy as well. You don't want a voltage differential in your readings so you definitely want to ground your LC-1 at the same point as your ECU (assuming you're feeding the output back into the ECU) or datalogger if that's what you're using. Then ground the heater ground to a separate point as per the docs. This will make even the old LC-1's last forever in my experience....  See the FAQ entry below for more info on this.



How should I wire up my Innovate LC-1 or MTX-L?

For the most part you'll follow the 'Quick Start Guide' that comes with the controller to the letter.  If you lost that or need a copy of it for some reason you can download it here:  LC-1 Quick Start Guide for the LC-1, LC-1/XD-1 Standalone Gauge Kit  if you have the combo kit, or MTX-L Manual for the MTX-L.

Here is what we'd like to add:

  • Ground the controller and the MegaSquirt together.  This is to prevent a voltage differential and will ensure accurate readings.
  • The factory EFI system's fuel pump relay often makes a good source for 12v switched power.  This is a required source for 12v, but often a good one...
  • For the LC-1, wire the brown (analog out 2) wire to the MegaSquirt's O2 input wire. For the MTX-L and LC-2, the default analog outputs are reversed, so you'd wire the yellow (analog out 1) wire to the MegaSquirt's O2 input wire.


For any LC-1 purchased after June2006, that should be all you need to be concerned with when wiring it up.



THIS STEP IS ONLY ON 'older model' LC-1'S as defined above (and below actually)Use a 470 ohm, 1/4watt resistor in between the analog output of the LC-1, and the o2 input of the MegaSquirt.  So you'll wire the analog output from the LC-1 to one side of the resistor, and then you'll wire the MegaSquirt 02 input to the other side of the resistor, forcing the signal to pass through it.

  • Blue Box or White/Red box LC-1's (started shipping around mid-June '06) have an updated DAC that does not require the 470 ohm resistor when used with MegaSquirt.  Another way to identify if you have this updated LC-1 that doesn't need the resistor is the serial number will be LC11188 or above, or the serial number will start with CLC on new models.


How should I wire up my Innovate LM-1 or LM-2?

For the most part you'll follow the 'Quick Start Guide' that comes with the LM-1 / LM-2 to the letter.  If you lost that or need a copy of it for some reason you can download it here:  LM-1 Quick Start Guide
LM-2 Quick Start Guide

Here is what we'd like to add:

  • If you are simply using the LCD display on the LM-1 / LM-2 to tune your car you have nothing different to do.  However, if you are routing an analog output from the LM-1 / LM-2  into the MegaSquirt you should ground the LM-1 / LM-2 and the MegaSquirt at the same point.  This is to prevent a voltage differential and will ensure accurate readings.  I've been know to clip the cig lighter connector wire that comes with the LM-1 / LM-2 and put quick disconnects on it, and install the same type of quick disconnect connectors on the MS Harness so I can pull power and ground from the same source it pulls from, ensuring the MegaSquirt gets an accurate sensor reading. 

Note-- You don't ever need the 470 ohm resistor with the LM-1 or LM-2.


How do I configure TunerStudio for the Innovate LC series, MTX-L, or LM-1 / LM-2?

For a long time we guided customers on how to re-program their LC-1 / LM-1 / LM-2 to output a slightly different signal from default.  The goal of this was to increase the resolution of the signal in the range of AFR most users will spend their time in.  What we used to recommend was to program the output you were using to send a signal that represented a 10-20:1 AFR from 0-5v.  While in theory this is great and does increase resolution a bit, in practice it's not really needed and is probably more trouble than it's worth for most users.  The benefit of this is almost immeasurable, so going forward we recommend leaving the analog outputs on your LC-1 / LM-1 / LM-2 at their default settings (which is 0v = 7.35:1 AFR, and 5v=22.39 AFR).  Then to configure the TunerStudio tuning software to allow your MegaSquirt EMS to properly talk to your LC-1 / LM-1 / LM-2 do the following:


With your TunerStudio project open, go to:
File > Project > Project Properties and click on the Settings tab
Under EGO O2 sensor, chose the right option (Innovate LC-1 Default) for your wideband in the drop down menu and click Ok.  TunerStudio will quickly restart and take you back to the main dashboard.

Next, click on the Basic Settings tab and chose Exhaust Gas Settings.  You will need to change your EGO Sensor Type to wideband.  Burn the change to your MegaSquirt.

Your AFR Targets Table will open underneath the More Settings tab.


With your TunerStudio project open, go to:
File > Project > Project Properties and click on the Settings tab
Under EGO O2 Sensor, chose the right option (Innovate LC-1 Default) for your wideband in the drop down menu and click Ok.  TunerStudio will quickly restart and take you back to the main dashboard.

Next, click on the Basic Settings tab and chose EGO Controls.  You will need to change your EGO Sensor Type to wideband or dual wideband as appropriate for your setup.  Don't forget to burn the change to your MegaSquirt. Lastly you will need to go to the Tools menu up top and click on Calibrate AFR Table.  Chose your sensor type (Innovate LC-1 Default) in the drop down menu, and click on Write to Controller.  This is a one way flash, so don't be alarmed if your settings don't 'stick' in this menu after you've sent them to the controller.  After the write is complete, click Close.

Your AFR Targets Table will be under Basic setup > AFR Table 1


With your TunerStudio project open, go to:
File > Project > Project Properties and click on the Settings tab
Under EGO O2 Sensor, chose the right option (Innovate LC-1 Default) for your wideband in the drop down menu and click Ok.  TunerStudio will quickly restart and take you back to the main dashboard.

Next, click on the Fuel settings tab and chose AFR/EGO Controls.  You will need to change your EGO Sensor Type to wideband.  Most setups will use a single sensor with the input received on DB37 Pin 23.  If this is the case for your application, enter 1 for Number of sensors and set your EGO Channel to Normal EGO.  This is a pink wire labeled "O2" on our harness.  If you are running multiple widebands, you will be able to set that up in this menu as well.  Don't forget to burn the change to your MegaSquirt when finished.

Lastly you will need to go to the Tools menu up top and click on Calibrate AFR Table.  If  the option for Calibrate AFR Table is grayed out, you will fist need to go to Tools > Un/Lock Sensor Calibrations, choose Unlocked, and Burn and Close.  Then you will be able to access the Calibrate AFR Table menu under Tools.  Choose your sensor type in the drop down menu (Innovate LC-1 Default), and click on Write to Controller.  This is a one way flash, so don't be alarmed if your settings don't 'stick' in this menu to be later viewed again after you've sent them to the controller.  After the write is complete, click Close.  If you desire, you can lock your sensor calibrations again by visiting the Tools > Un/Lock Sensor Calibrations menu again.

Your AFR Targets Table will be under Fuel settings > AFR Table 1



Shipping / Customs:


Will you reduce the value of my order on the customs paperwork or mark it as a 'gift' so I pay less in customs duties/taxes/import fees?

We do get asked this frequently and we wish there was some way to ethically avoid these taxes and fees for our international customers but unfortunately there isn't.  We must properly fill out all customs paperwork and include a receipt with your order.  We made a commitment early on in running our business to be 100% straightforward and honest in all of our dealings, with our customers, vendors, and even the tax-man.  We hope you understand and even find comfort in knowing that we're committed in being 100% straightforward with you as well.  We do appreciate your business and will continue to strive to keep our prices affordable.  Thanks!


Do your prices include sales tax? What about VAT?

Prices do not include taxes. Orders inside the state of Georgia are subject to a 6% sales tax. We do not collect taxes on orders to other states or international orders; there is currently no national US sales tax. Most international orders are subject to tariffs or taxes upon arrival. This is collected by the government in the country the order was shipped to, and has no control over these taxes. We do not have the most up to date information on these tax rates, either, so we recommend checking with your local customs office for the most up to date information.




Other FAQs

Main MegaSquirt FAQ  This is the main MegaSquirt FAQ, as well as the MegaManual.  You will do well to become one with the MegaManual.  Let it flow through you.  Use the farce!

Matt Cramer's MegaSquirt FAQs  Some may be a bit outdated as this was Matt's FAQ from years ago, before he worked here, still good information to keep available though.

Innovate Motorsports FAQ  Frequently Asked Questions on Innovate's Wideband Products straight from the pros at Innovate.


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Performance testing & tuning by LoadStorm.