99-05 MS3 with MS3X

View at Picasa Notice the piece I had to cut out and glue to the top lid.

Parts needed:
1x MegaSquirt-III w/PCB V3.0 - UnAssembled Kit
1x MegaSquirt-III MS3X Expansion Card
1x MSPNP and DIYPNP IAT Sensor Kit - Steel Bung
+ parts for the miata specific alternator mod (required)


About
This is a how-to for a full plug and play 99-00 MS3.  This build does not use the DB37 connector but the miata specific 48/64/76-pin connector which can be installed inside the case with a minor modification to the MS3 card (I’m not sure if the 76 pin fits, test before starting to cut things up!).
One circuit is built in the proto area to control the alternator.
The euro 1.6 is identical to the 1.8, except for the VICS which is not present on the 1.6.
The 01-05 cars have no VICS, but VVT.
Apparently, the wiring for the 01-05 can be different than the earlier cars.  On the ’04 MSM at least, power isn’t wired like the ’00, 4S is key switch on power, NOT4AF.
Until you ground 3H (to turn on the main relay), 4AF doesn’t have power.  It’s probably easiest to use a spare INJ output to ground 3H as soon as you turn on the ignition (activate the INJ output when coolant >-60 degrees or so).  See also this thread.

View at Picasa Install these components from the kit. A couple of extra components are added for alternator control, cam input pullup and low battery light (optional)

View at Picasa Install only these components from the MS3 kit

The only transistor on the heatsink is U5 (no mica insulator needed) on the far left.  With a near empty heatsink, there’s enough room to put the miata connector inside the case, bolted to the heatsink.  You can use 2 existing holes in the heatsink for it.
In the picture, I installed the idle circuit (R19, R39, D8, Q4 and Q20), but that’s not necessary because the MS3X card will control idle.  I installed those parts to have a spare PWM output.

Pictures
You can find all pictures here:

Megasquirt MS3 + MS3X 1st buildOct 12, 2011Photos: 14

Overview
This chart shows all possible in- and outputs on the MS and how we’ll use them.

There’s several unused pins on the miata specific connector, so I wired up several spare wires.  That way I won’t have to take the Megasquirt back out of the car in case I need some extra functions in the future (like COPs for example).

Software
The MS3 release can be found here.
A starting msq can be found here (use with care).

The build
Start your MSIII V3 build as described in the build manual here.
Just follow the manual along with my instructions.

Step 1 to 6: only install the DB9, R1 to R11, R16, R24 to R29, R40, R42, R44 to R56
Step 7 to 11: only install D4, D9 to D13, D19, D24
Step 12 and 13: skip
Step 15B: install
Step 16: only install U6, U7,  and the 40-pin socket
Step 17: skip
Step 18: place the heatsink on the PCB and secure by installing U5 and a temporary bolt on the other end.
Step 19: skip
Step 20: install U2, Q2, Q19, Q6 to Q8, Q22 and Q23
Step 21 to 22: skip
Step 23: install the wire
Step 24: test
Step 25: install D14 to D16 (LEDs)
Step 26 : skip
Step 27: jumper TACHSELECT to VRIN and jumper VROUT to TSEL
You need to add a pullup to the VR circuit.  Install a 1k resistor in the left hole of R13 (= 5V). Connect the other end to the right side of R45 just below it (= VRIN)
Turn both pots (R52 and R56) about 12 turns to the fully anticlockwise position (you may feel a “click”) and then turn R56 back about 6 turns clockwise.
Run a wire from 2J (GY/R) of the 64-pin connector to TachIn (pin 24) on the DB37.  This is your crank input signal.
Step 28: skip
Step 29 and 30:

View at Picasa You need to cut off this corner in order to clear the 64-pin connector. It's no big deal, the copper layer starts much lower.

In order to install the 64pin connector inside the case, you need to cut off a corner of the MS3X card.  As there’s no copper in that area, you can safely cut it off. 

View at Picasa Use a plastic bolt and nut under the standoff so you don't damage the pcb. A couple of washers are needed on top, to close the gap.

The stand-off on U5 was a bit too long in my case so I cut off a mm or 2.  The other stand-off can be used in the left bottom corner of the card, in an existing hole in the PCB.  Be sure to use a plastic bolt and nut so you don’t damage the PCB.

Step 31: You need to remove the DB37.  It can be taken apart very easy by prying out the back cover.  Once apart, all the pins can be desoldered one by one.  Takes about 15 mins or so.  A desoldering pump comes in quite handy for this.
Install JP3 and JP7 (pullup for the VR circuit).
Turn both pots (R11 and R32) full anti-clockwise – approx five turns. Then turn the top one (R11) two turns clockwise.

MS3X Idle circuit modification

It’s optional but strongly adviced to install a flyback diode over the idle valve.  Without it, the idle pwm % will be around 70, whereas you want it to be around 30 for best control.
Install a 1N4001 with the banded side to 12V and the other side to the idle output of the MS3X (pin 9).  I soldered it directly on the Tyco connector.

Fine adjustment of the VR circuits

For the main board, measure the voltage between R54 and pin 3 of U7 while turning R56. On the MS3X board, measure between R17 and pin 3 of U7 while turning R11. In both cases, you want to see about 2.5 to 3 volts at that point, which puts you right in the middle of the actual output range of the sensors.

Alternator Mod

View at Picasa alternator charging circuit

View at Picasa Alternator control circuit in the proto area. Notice the resistor from Q12 pin 3 to top of R3. It normally goes in Q12 pin 2 and 3, but pin 2 is taken by the 12V feed.

Megasquirt cannot directly control a ’99 alternator, so you need to build a regulator in the proto area (or install a 90-97 alternator).
The setpoint is determined with the formula: 2.495V*(1+ R4/R11), so it’s important to use 1% resistors for R4 and R11.

View at Picasa alternator charging circuit in proto area

Testing the circuit is done by measuring the output on the Field wire.  Measure the output while increasing the input voltage of the board.  The output should follow the input up to about 14.4V and drop to zero when you keep raising to above 14.4V.
You can take 12V from S12, but I took it from the left side of D3 (anode) as it was closer by.  Run the output to 1O (GY/R) in the 64-pin connector.
This is how you order the components in the proto area.

Alternator Warning Light (optional)

Use a spare output on the MS3X to activate the alternator warning light when battery voltage is <12V or >15.5 or so (whatever you prefer).

Result

View at Picasa wiring goes nicely between the main board and the MS3X

View at Picasa Wires between the 2 pc's. No DB37 on the MS3X

This is what the PCB looks like with all components installed.

Wiring
I cannot stress enough the importance of grounding properly.  All kinds of problems can occur as a result of grounding the MS to the chassis.

The proper grounding should be:
1) Several wires from both MS3 connectors all the way to a ring terminal *on the engine*.  Do not combine the ground wires before you get to the ring terminals. It is preferable that you run all 5 ms3x ground wires out to the engine.
2) 2 or more larger ground wires from the engine to the chassis.
3) A large ground wire from the battery negative to the chassis.

Ready more about grounding here.

When you start soldering wires to the tyco connector, go left to right (right handed) on the bottom row and then the top row, so you don’t block anything off.

99-00 MS3+MS3X pinout

You need the 64 Pin Male connector (Tyco 174518-7), available from onlinecomponents, mouser or digi-key.
I found it easier to run a wire from 1B to Q12 pin 2 instead of going to the DB37.

View at Picasa Tyco 174518-7 (64-pin connector)needed on 99-00 but also fits 90-95

01-05 MS3+MS3X pinout

You need the 72 Pin Male connector (Tyco 1123038-2), available from onlinecomponents, mouser or digi-key.
I found it easier to run a wire from 1B to Q12 pin 2 instead of going to the DB37.

View at Picasa Tyco 1123038-2 (72-pin connector)fits 01-05 only