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 MegaSquirt II V3 How To 
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Post MegaSquirt II V3 How To
Ok, I know that there are not too many people here who know much about MegaSquirt and the ones that do are not all that active. So I decided to put this together to hopefully help anyone else looking to Squirt their Mx-3. I am by no means an expert on MegaSquirt, and there are several other sources of info out there including ProbeTalk and MSEFI.com. However, I have had a hard time getting help from PT and MSEFI is too vague since it is not specific to our application. For the record, I bought a MSII with a V3 pcb (printed circuit board), sold as a kit from DIY Auto Tune and I assembled it myself. DIY sells the kit with the face plates already drilled out for the LEDs and things. I am not sure if they all do. I am running a N/A KLZE with standard 220cc/m injectors (stock on the ZE) and am still using my Mx-3 distributor.

MegaStim:
Ok, I built the board myself and HIGHLY recommend buying the MegaStim if you are planning on building it yourself. That is HIGHLY like Really Really! It allows you to test your board as you build it so that you can make sure you are not messing up. Basically like a checkpoint in a video game. If you die...you start over from the last check point. It took me over 12 hours to build the Stim and MS Boards...but I was a soldering rookie. It also lets you do all your initial set up before you wire it into the car and will give you a chance to play with and learn the MegaTune software. It eats 9V batteries like a SOAB, so keep that in mind. You will commonly get a message like, low battery cannot burn. Do you want to try anyway? Always do. If it asks you twice, that means the battery is toast. Also, if it gets too low, your computer will start beeping at you. This is the MS resetting and it is not good for it so try not to let the battery get too low.

Relay Boards:
Basically they offered this because a lot of people wired things up wrong on their car and fried the MS. I don't think that they are needed, but I was extremely careful in wiring mine up and made sure that I was connecting the right wires and they were high quality connections with no chance of shorts. So, It all depends on how focused you can be. If you are not detail oriented...you might want to buy the relay board but honestly I think it is a waste of money.

Assembly:
There are a few decisions that you have to make while assembling the board that require you to know things that aren't common knowledge. A few things I learned while building the board for example were.
-Our Idle Air Control (IAC) is a Pulse Width Modulation (PWM) unit, not a solenoid or a stepper motor. You can set it at different duty cycles for different temperature values in MS.
-The Mx-3 was ahead of its time in that it came with sequential fuel injection. This just means that each injector fired independently and exactly when it needed to in the engine cycle. Pretty cool, even though it is not hugely important. What is important is that MegaSquirt will not support Sequential Fuel Injection without modification, so to use MS you are going to be using Batch fuel injection, usually one bank at a time. Some people stagger their injectors (1,4,6 on one wire and 2,3,5 on the other wire.) as they say it keeps the fuel pressure up in the rail. I don’t think it matters one bit since both fuel rails run from the same fuel line and through the same FPR. Either way, it doesn’t matter.
-Our fuel injectors are High Impedance injectors and there are instructions in the MegaManual about how to build and configure your MegaSquirt to run them. There are 2 settings on the Injector Characteristics page that you have to change. Your car will not run without these settings done correctly…I can personally attest to that. HAHA!
-On the V3 board, it is best to set up both the Hall and the VR (Variable Reluctor) options. You use a jumper to select which one you want to use depending on where you are getting your tach signal. If you are using your stock distributor like I am. You can simply patch into the tach signal that runs from the Hall sensor in the disty. A lot of people end up ditching the distributor all together in favor of external coils or coil packs. If you do this, you will need to use the Crank Angle Sensor to get your tach signal and you will end up having to grind one of the teeth off of your Crank Pully to tell the MS where cyl. #1 is. Not just any tooth…look on ProbeTalk for the how to.

Wiring:
Wiring it up is a piece of cake if you are piggybacking. I would still recommend that you do it in a way that you can easily go back to using your current ECU so that you can drive it if you encounter any problems. I used spade connectors on the wires that I cut from the engine harness. All the other wires, I just taped into with quick taps from Home Depot. If you are going to be running MS stand alone, a clean way I thought of to do it would be to get your hands on the female ports of an ECU, and wire the corresponding pins to the MS…then all you would need to do is plug the stock wiring harness into those female ports and thus right to your MS. This is of course only if you ever want to be able to put a stock ECU back in. If not, just make your own wiring harness and run it all the way to the connectors on your sensors. Attached is a wiring diagram for how to wire the MS into the wiring harness. I modified it from a Probe application to match the 93 Mx-3 GS wiring. Even if you have a different year V6 the ECU pins should still be the same, but you should check to make sure.

Tuning:
I will let you know when I know. I have tried a few maps that I have found on the net, but none of them seem quite right.

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April 17 2007, 12:36 AM
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NIce! Made a stickty!

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April 17 2007, 9:56 AM
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Awesome!! good stuff man :wink:

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April 17 2007, 11:41 AM
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what do you mean by 'cut wire at ECU, plus into injector/disty" ?

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April 17 2007, 7:15 PM
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I guess I need to go into a little more detail. I am still using my KL36 ECU to control spark, Fans, Vris and the A/C that doesn't work. I will make it stand alone soon enough, but to piggyback all you need to do is splice into the wires that run to your current ECU as shown above. Then you have to cut all 6 wires for the injectors since you would have the ECU still trying to control fuel otherwise. Then you wire 3 injectors to each MS wire. Maybe this wiring diagram will help you visualize. Just ignore the writing on the picture. You really only need to cut and splice the disty wire if you are running an external coil set-up which I am not. So I don't even have this wire attached to the cars wiring harness.

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April 17 2007, 10:49 PM
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could to map that wiring diagram onto a B6 ECU ?

if you gots time sometime...

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April 18 2007, 12:12 AM
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I wouldn't want to do that. The only reason I posted this is because I know that it works, because I wired it into my car. Since I know little about the B6 I wouldn't want to tell you something that I couldn't prove worked. All you need to do is get a Mx-3 wiring diagram and it will tell you the ECU pins and wire colors for every wire in the car. You need to make sure that the wiring diagram is for the right year and model Mx-3 and for the type of tranny you have. Wiring for an Automatic might be totally different.

Here is a link to a wiring diagram for a 1993 B6 with a Manual Transmission:
http://www.mx-3.com/phpbb2/viewtopic.php?p=410010#410010

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April 18 2007, 10:49 PM
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Post Re: MegaSquirt II V3 How To
Damn, edging towards a year since the last post in this thread.

Just a question, you have both your VRIS being triggered at the same time on the same X5 output rather than seperately?

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March 24 2008, 11:49 PM
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Post Re: MegaSquirt II V3 How To
I did as you said in your sticky about the megasquirt.

I used the stock ecu pinouts and hooked them up to the megasquirt.

I am having trouble with the tach signal though. I am reading everything else fine, but the car can't start without the tach signal.

I hooked up the tach input to the ne1 pin on the factory harness....and no go..

any ideas?

also, I have tried the 5v pullup resistor from the ign to the 5v power source with a 280ohm 1/4watt resistor, and that didn't help.

cheers

7

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April 12 2008, 6:31 PM
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Post Re: MegaSquirt II V3 How To
I am having the exactly problem does anyone have an answer towards a solution to this problem????


February 11 2010, 1:47 PM
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Post Re: MegaSquirt II V3 How To
I did find a solution to this problem, but for the life of me I can't remember what I did. I sold the car now as well.

It is fixable though, try the guys at probetalk,as I think that is where I got my fix from

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February 11 2010, 5:49 PM
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Post Re: MegaSquirt II V3 How To
so ive been thinking of buying a megasquirt. im pretty good with wireing.
is it pretty simple to set up.
i mean do the directions leave you puzzled?
and your saying that you have your old ecu and the megasquirt running?
im a little confused.

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February 12 2010, 1:03 AM
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