DIY Megasquirt Installation

[cenatix]

Ok guys, I will share my Megasquirt setup with you all and do my best to do a step-by-step how-to. Please keep in mind this is not a complete how-to and that there is much more to it besides the hardware configuration. Every setup is different, therefore, each MS will need to be configured for YOUR car. Also, this is not the only way to get your 1st gen running on MS but it is one of the more easier methods. If anyone would like to share their MS setup, feel free do to so.

Before even attempting to do this, it is HIGHLY recommended you read the MS and Extra Manuals:
MegaSquirt - Electronic Fuel Injection Computer by Bowling & Grippo * * ©2005
MegasquirtnSpark-extra
MS-Extra Manual Index

Megasquirt Support Forums:
MegaSquirt EFI :: Index
MSx/Extra EFI :: Index

My Megasquirt Setup:

-v2.2 PCB (older, "green" PCB)
-MS-1 Processor, loaded with 029v Extra firmware
-VB921 High Current Driver
-No relay board or flyback board
-N/A distributor with locked mechanical advance
-Innovate LC-1 Wideband Controller

I own a 1989 MX-6 GT and the harness wire colors covered here will pertain to the years of '88-89 (Mazda 626/MX-6 GT) and '89 (Probe GT). If you own a 90+, the harness wire colors will be different. I am using the cheaper v2.2 PCB which has worked fine for me. I would recommend the v3.0 (blue) pcb over the v2.2 because overall, it is a better design and plus it already has the vb921 driver. This will cover the v2.2 pcb only but should be fairly easy to covert over to the v3.0 pcb.

First of all, get yourself a Megasquirt unit. Either a pre-assembled unit or "kit" which you will have to solder together all the components. If it wasn't for my horrendous soldering skills, I would have opted for the kit. Also, you'll need a vb921 driver with a 330 1/4 resistor to use with the v2.2 PCB. The vb921 driver lets you directly drive a coil without the need of an ignition module.

MegaSquirt I Programmable EFI System PCB2.2 - Complete Assembled Unit DIYAutoTune.com

MegaSquirt 'ModKit' - VB921 High Current Ignition Coil Driver with Bias resistor DIYAutoTune.com

Needed components/parts:
-22ga. wire
-0.47uf capacitator
-1K ohm resistor
-Intake Air Temp Sensor (click below for more info)
Wiring and Sensors

[PCB MODIFICATIONS]
Refer to this diagram for component locations:
http://www.megamanual.com/v22manual/pcball.gif

-Remove D8 (if installed)
-Remove XG1-XG2 jumper (if installed)
-Jumper Pin 24 to JP1 Pin8
-Jumper XG1 to X11

1.) Leg #1 of the vb921 to the 330 ohm resistor. Then jumper a wire to the RHS (right hand side) of R25.
2.) Leg #2 (coil out) to X13. From underneath the board, jumper a wire from X13 to pin 29 of the DB37. The reason to double it up is because the vb921's current is greater than what the trace of X13 could withstand (X13 goes to pin 29).
3.) Leg #3 (ground) goes to JP1 pin 7 (or another ground source)





This modification will result in the following arrangements of the DB37 harness:

-Pin 24 = 5v OUT (to distributor)
-Pin 25 = Tach signal IN (from distributor)
-Pin 29 = Coil signal OUT (to neg. side of coil)

Mount the VB921 on to a proper heatsink (i.e. MS case)
Also, this modification will make the Stimulator not function correctly. The Stim expects the tach signal to appear on pin24 but instead, it will appear on pin25.
http://megasquirt.sourceforge.net/ex...ver-extras.gif

[DISTRIBUTOR MODIFICATIONS]
With a N/A distributor (year doesn't make a difference), you'll need to take it apart in order to lock it. Locking it enables you to have complete control over the timing.

First, you'll need to remove the 4-tooth rotor wheel. You'll need to pry it from the shaft with a large screw driver or pry bar. Use extra when removing the screws, caution because they will strip easily especially the ones on the housing. It is very important that you install the 4-tooth rotor wheel the same way before you removed it or your timing will be off. Once you have the distributor sensor removed, you'll see the weights for the lower shaft of the distributor. You will want to "lock" it so both the upper and lower shafts move together. A tack weld is all it takes.



For the vacuum advance, all you need to do is to keep the vacuum lines unplugged.

The blue wire goes to pin 25 (Tach signal) of the DB37 harness. The black/white wire is the 5v+ wire for the sensor and goes to pin 24 of the DB37 harness.



Attach the 1k ohm resistor (pull up) to the the blue and black/white wires on the distributor. Refer to the Extra Manual under "Setting Up" for more explanation of the pull-up resistor.


[WIRING]

You have a few options with wiring. You can tap into your existing harness, make your own harness, or make a "Plug 'n Play" harness. The latter option, you will need to take the female socket from the stock ECU (either a non-turbo or turbo one will work) and solder the pins of the socket to the wires on the DB-37 harness. I chose to do this route. This enables you to keep the stock harness intact without hacking any wires (i.e. if you want to switch back and forth from MS and the stock ECU). This is when a wiring diagram will be extremely helpful.



A helpful way to figure out where the location of each pin is to look at the ECU. When you remove the female socket, you'll see the ECU Pin labeled on the board.

MS Function - [MS Pin] - [ECU Pin] - [ECU Color]
Grounds - [7,8,9,10,11] - [***] - [***]
TPS Ground - [19] - [2C] - [Light Green/Yellow]
Intake Temp Sensor - [20] - [***] - [***]
Coolant Temp Sensor - [21] - [2I] - [Yellow/Black]
Throttle Position Sensor - [22] - [2G] - [Light Green/White]
O2 Sensor - [23] - [2D] - [Black]
Distributor 5+v - [24] - [***] - [Black/White*]
Tach Signal IN - [25] - [***] - [Blue*]
TPS 5+ Vref - [26] - [2A] - [Light Green/Red]
12+v Power - [28] - [3I] - [Red/Black]
Coil Signal OUT - [29] - [***] - [***]
PWM Idle Valve - [30] - [2Q] -[White]
Injector Bank #1 - [32/33] - [3E] - [Yellow]
Injector Bank #2 - [34/35] - [3C] - [Yellow/Black]
Fuel Pump - [37] - [2O] - [Light Green]

*Color on the N/A distributor; not part of GT harness
*** Do not tap into the ECU harness. Instead, just run a separate wire to the sensor.

For the MS ground, I ran the wires to the Negative side of the battery. The battery acts as a filter for any noise.

Since my stock coil failed, I replaced it with a Bosch coil for a Volvo. I ran the 12+v to the fuel pump relay and the negative side goes to pin 29 of the DB37. I put the 0.47uf capacitator on the + of the coil and then to a ground source. This will reduce any noise.



If you're making your own DB-37 harness, please visit Wiring and Sensors for more info.

The easy part is done, now onto the difficult task of tuning
I will post up a .msq file soon for the stock injectors and get it to idle.

For now, enter your constants in MegaTune and use a Trigger Angle of 60 and set your Fixed Angle to 10*. With a timing light, rotate your distributor until you see 10* on the crank pulley. If you can't get your distributor to 10*, then adjust the trigger angle accordingly until you can do so. Then set the Fixed Angle to -10 to go back using your Spark Map. I don't have the time to explain every function, nor does anyone else so read the manual and familiarize yourself with everything so you don't blow up your engine.

[Panther37]

Find Comments here (Comments on: DIY Megasquirt Installation).