Oochi's MS3X DIY Build
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Hello, I got all (most) of my MS3X parts in and I have started the build! This is for a 90 with stock 1.6 btw. I figured I would make a build thread because I know I will have questions and don't want to screw this up, plus you guys know more than me. anyway, So far it has gone quite smooth. A couple things that I am confused about. I got the resistors in, then diodes, now working on capacitors. One thing I am confused on is I have a resistor in a baggy by itself labeled "BIP373 330o, 330QBK-ND" i know it is a 330ohm resistor, but i cannot find it anywhere in the manuals. I have been using www.msextra.com as a reference. Another thing is...
I'm not sure what this means! Please review my progress and let me know what I do wrong, or any other recommendations. I will update this as often as I work on it. Will be during weekends due to college.
PICS:
![](https://www.miataturbo.net/attachments/megasquirt-18/32152-oochis-ms3x-diy-build-2012-01-20182427.jpg?dateline=1327129046)
![](https://www.miataturbo.net/attachments/megasquirt-18/32153-oochis-ms3x-diy-build-2012-01-21000135.jpg?dateline=1327129046)
12) Next get all the bags of capacitors together, keeping them in the bags (C1, etc).
If you’re using the coil –ve as the trigger input go to step 15 (This is rare now.) Note that you CANNOT trigger from coil negative if you are trying to run ignition or sequential fuel - you need a trigger-wheel arrangement.
13) As long as you’re NOT using the coil –ve as the trigger input (Fuel only) find C30 and instead install it in H1/Boot (This adds smoothing to the battery voltage measurement and reduces the chance of noise getting injected into the CPU from the 12V line.)
If you’re using the coil –ve as the trigger input go to step 15 (This is rare now.) Note that you CANNOT trigger from coil negative if you are trying to run ignition or sequential fuel - you need a trigger-wheel arrangement.
13) As long as you’re NOT using the coil –ve as the trigger input (Fuel only) find C30 and instead install it in H1/Boot (This adds smoothing to the battery voltage measurement and reduces the chance of noise getting injected into the CPU from the 12V line.)
PICS:
![](https://www.miataturbo.net/attachments/megasquirt-18/32152-oochis-ms3x-diy-build-2012-01-20182427.jpg?dateline=1327129046)
![](https://www.miataturbo.net/attachments/megasquirt-18/32153-oochis-ms3x-diy-build-2012-01-21000135.jpg?dateline=1327129046)
![](https://www.miataturbo.net/attachments/megasquirt-18/32154-oochis-ms3x-diy-build-2012-01-20235737.jpg?dateline=1327129046)
Last edited by Oochi; 01-23-2012 at 11:05 PM.
#3
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well thats just great! would it hurt to leave whatever isnt needed in there? and are you saying to follow http://westfieldmx5.devocht.com/mega...egasquirt-ms3/ and http://www.megamanual.com/ms2/V3assemble.htm ? I was just following the directions that diyautotune sent me to look at.
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Long story short: You can build the unit "fully" according to the primary documentation and nothing is lost. Since you are using the MS3X, your build will be particularly simple as you needn't bother with any of the old-style "hacks".
As to the quote in your first post, you are not going to be triggering from coil -ve. That applies only to cars with distributors and breaker-point ignition. (Remember, the MS project has its roots in the old-school American Iron community. They see nothing wrong with distributors, throttle-body injection, separate water fountains for brown people, and arranged marriage.)
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Good luck Oochi, I'll be watchin'
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And that is what really gets me about the MS and why I paid Scott to build one. I want to do a carb -> EFI project in the future but figuring out the MS2 documentation is a bloody nightmare. I'm just glad you guys who DO understand it are willing to give advice/suggestions/abuse to help keep us noobs pointed in the right direction.
Good luck Oochi, I'll be watchin'
Good luck Oochi, I'll be watchin'
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Study this http://www.megamanual.com/ms2/pcb.htm
Look up the parts that you're not sure about and see what they do.
U3 is the opto-isolator, so if you need it or not depends on how you wire the tach inputs.
Brain's diagram assumes you use the opto circuit (U3) as crank input and JS10 as cam input as discussed in this thread.
My diagram assumes you use the VR circuit (U7) as crank input and the VR circuit on the MS3X asd cam input.
Same result, done differently.
The only transistor you need on the heatsink is U5. The rest of the parts on the heatsink are for the injector circuit, but you can leave those parts out because you use the injector outputs on the MS3X instead of those on the main board. IOW, everything you installed on the heatsink up to now, including R37 and R38, is not needed.
Same thing with the idle circuit, you use the one on the MS3X instead of building the one on the mainboard.
You really need very little parts from the mainboard.
Look up the parts that you're not sure about and see what they do.
U3 is the opto-isolator, so if you need it or not depends on how you wire the tach inputs.
Brain's diagram assumes you use the opto circuit (U3) as crank input and JS10 as cam input as discussed in this thread.
My diagram assumes you use the VR circuit (U7) as crank input and the VR circuit on the MS3X asd cam input.
Same result, done differently.
The only transistor you need on the heatsink is U5. The rest of the parts on the heatsink are for the injector circuit, but you can leave those parts out because you use the injector outputs on the MS3X instead of those on the main board. IOW, everything you installed on the heatsink up to now, including R37 and R38, is not needed.
Same thing with the idle circuit, you use the one on the MS3X instead of building the one on the mainboard.
You really need very little parts from the mainboard.
Last edited by WestfieldMX5; 01-29-2012 at 04:47 PM.