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MEGAsquirt A place to collectively sort out this megasquirt gizmo

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Old 07-24-2008, 05:38 AM   #1
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Default It's been done before but I felt like sharing

Some pics of my megasquirt. Should be running the car by the weekend, just waiting on an air filter and piece of pipe to put AIT in.

I built it in a stock case as you can see but I added "on board" USB-RS232 communication (the red heatshrinked block at the top) and a nice plug for the LC1 (which is also a great way to power the MS while on my bench)

The (almost) finished product
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It's nice to have a workbench for toys (sorry I just built it and feel the need to show people)

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Box of bits

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On test after building powersupply and proccessor coms. You can see the el cheepo usb serial adaptor (working so far) that I butchered to go inside.

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It lives!!

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If you are wondering why I went to the effort for this and some of my other mods its because I have an irrational fear of touching the cars wiring. I dont mind repairing it but I really hate it when I buy something and someone have bodged it up in someway. So far everything I have done can be reversed in about 1/2 a day.
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Old 07-24-2008, 06:20 AM   #2
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That's Sweet, nice job.... wish someone could built me one!
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Old 07-24-2008, 06:44 AM   #3
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Order up a kit from DIYautotune and post it my way. I had so much fun doing mine I wouldn't mind helping people out. Send an ECU and I'll even make it a DIYPNP
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Old 07-24-2008, 10:16 AM   #4
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Nice job.
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Old 07-24-2008, 10:19 AM   #5
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nice job duck- very tidy
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Old 07-24-2008, 10:24 AM   #6
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Nice job.......I like it, kinda rings a bell

What's the BNC-looking connector for?

And what looks like 6 or 7 wires coming out of the DB9 side...you really only need 3. Or 4 if you need +5V out.
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Old 07-24-2008, 10:53 AM   #7
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Imitation is the highest form of flattery

The BNC connector is actually a locking DIN socket from my audio engineering days. It's a once stop shop for connecting the LC-1 and also a useful way to provide 12v whilst its on the workbench.

I just put all the wires on the DB9 for the hell of it. I was out in the garage and couldn't be bothered to come back in to work out which 3 I needed
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Old 07-24-2008, 01:33 PM   #8
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Duck, my friend, that is an absolutely gorgeous build. The locking circular connector on the side is just pure brilliance, and I love what you did with the built-in RS232 to USB adapter.

I see that the position normally occupied by the MAP sensor is empty. Are you planning to mount the sensor outside of the case, or is it stuck in there somewhere that I didn't see?

Interestingly, here in the states a "DIN" connector is a bit different. They're still circular and polarized, but non-locking. As an example, MIDI and older (8086-80486) computer keyboards use what we call DIN connectors. What you've got there is very similar to what we'd typically call an Aircraft connector, as that style of interconnect is common in high-reliability applications such as airplane wiring harnesses, and also found on pro video equipment such as OB cameras.
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Old 07-24-2008, 01:50 PM   #9
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Thanks Joe, The MAP isnt mounted yet. Its going to be external connected to . I'm having trouble finding a pinout for the MAP sensor can you hook me up?

The connector is the same as a DIN inside the locking housing, I used them for some of the old PA gear I worked with at school (yes I was the nerd who did all the sound for school productions )

I'm hoping by wiring the LC-1 into the MS itself I will avoid any possibility of ground loops.

Edit: You're quite right, its slightly different to a DIN. Maybe I used it for connecting the light dimmer desks.

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Old 07-24-2008, 02:13 PM   #10
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Old 07-24-2008, 02:23 PM   #11
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Very cool, and im very jealous that you dont have to deal with OBD.
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Old 07-24-2008, 02:25 PM   #12
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I found it. Might even cranck this bitch tonight

Edit: Thanks PF note to self - refresh before posting
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Old 07-24-2008, 02:41 PM   #13
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OK hit a brick wall. I need 3 wires for the MAP :(

On the MAF socket there is 12V, MAP sig, AIT sig, GND, SECOND GND, and no more pins for the MAP ref voltage.

Any Ideas? Any way I can use 12v as the ref voltage?
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Old 07-24-2008, 03:10 PM   #14
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I think I may have found it. The right most pin of the MAF socket (light green/black) goes to pin 2F but its also grounded according to the wiring diagram to the rear right of the engine along with 2 other wires. Anyone know where this grounding point is so I can remove it?

Pipe, I found this pic on your original thread

How did you get it to work with only 2 wires?

Mine just registers 100kpa even if I suck on the little nipple :S
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Old 07-24-2008, 04:28 PM   #15
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I didn't, the +5V out should actually read "Wire Pin 3 of MAP sensor to Pin D of AFM". Remember, this diagram is valid for a 1992 car, I am not sure how the 94+ is different. Are you sure the MAF is 12V and not 5V?? If its indeed 12V, share the TPS signal line (+5V) with the MAP sensor. or build a DC-DC converter (one of these perhaps: http://www.maplin.co.uk/Module.aspx?...C=SO&U=strat15) inside your MAP sensor box.
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Old 07-24-2008, 04:45 PM   #16
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the MAF is 12v
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Old 07-24-2008, 05:18 PM   #17
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Aaaawwww I FAIL and it was all going so smoothly

Does anyone know where the light green/black wire goes to ground? If I can unground it then we have a WIN situation.

http://www.madracki.com/miata/images/wiring/94sys.pdf (page9)
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Old 07-24-2008, 05:48 PM   #18
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light green black should go to rear of intake manifold on 90-93 and near throttle body on 94+ IIRC.
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Old 07-24-2008, 06:11 PM   #19
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Thanks Pipe, I found it on the stud by the TB just as you said. The pin is still grounded though! I'm gonna go hunting tomorrow in the daylight.
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Old 07-24-2008, 06:25 PM   #20
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Be careful of the black / light green wire! It is also the ground for the cam position sensor- if you unground it, the CAS won't work.

Here's what you've got to work with at the MAF:

1- White/Red = +12V from main relay. Useless.
2- Red/White = pin 2O of ECU. Useful.
3- Red/Black = pine 2P of ECU. Useful.
4- Black / Light Green = pin 2F of ECU, but also CAS ground and head ground (3). Cannot easily be re-used without separately grounding CAS.
5- Black / Blue = pin 2D of ECU, and also ground for TPS, EGR sensor, coolant sensor, and O2 sensor. Cannot easily be re-used without separately grounding all those other devices.

IOW- you're screwed. Run a decicated piece of shielded balanced audio cable such as Belden 1504, 9451, or 1800 from the MS straight to the MAP sensor.
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