I have purchased and began building an MS3 from DIY Autotune using the Megamanual (Assembly Guide - MegaSquirt(R) V3.0 Main Board). There are certain steps that require you to make decisions based on the vehicle. I can't seem to find anywhere which options to choose for the miata. Also I don't have an Ms3x, is it possible to do the build without one and what mods will this require? I have a 2000 with the stock 1.8 and I plan to use the MS as a standalone.

 

Doing it without an MS3 will multiply the amount of work you have to do by approximately 10x. Just ask @hi_im_sean

Read more. Franks guide should be out there somewhere. I think I have it hosted here too. http://sadfab.com/99-05MSGuide/99-05MSWestfield.zip

 

you want expander board.

follow frank's writeup. google "frank megasquirt"

I dont build the harness the way he does.

 

Thanks for the quick responses, I just ordered the expander. Just to confirm other than the harness I shouldn't need to order anything else, correct?

 

nope. ms3 kit + expander will run any 90-05 miata.

 

One more thing Brain, just a general question about forum courtesy; In the future as I undoubtedly will have more questions as I'm building the MS, is it better to reuse this this thread or start a new one?

 

wiring bundle for the ms3x is helpful.

Knock module is a good option to add.

 

One thing Frank's page isn't so good at is showing how he connects that 48-pin Tyco connector to the MS3. Anyone got any details on that?

 

Don't do it how he does it

 

I can document exactly how i build a harness this weekend for an alternative approach.

 

That'd be nice!

 

Start with a bored helper:




Populate the Mainboard DB37:




Populate the MS3 Expander DB37:





Acquire an OEM Harness connector:




Chop off the top pins so they are about 1/4" long:




Bend up the lower row so they are flat (try to actually fold them back straight):




Cut them flush to the top row:




Pre-tin the pins you'll be soldering wire to.
Put heatshrink on each of your wires. *SUPER IMPORTANT*
Pre-tin the wires.




Start soldering the Mainboard DB37 wires (I start from left to right, lower-rows to top-rows):



Follow up with MS3 Expander wires:




Melt the heatshrink so you ensure no wires will make a connection:




Follow that up with hot-glue so the wires stay secure and are less prone to vibration & stress:




And done:





You can populate the center connector for inputs and output, I used to do this, but lost my source for pre-populated connectors -- i hate crimping pins

 

So I end up with something like this:

 

Thanks so much, I'll be using your design for the harness now!

 

What is your source for the colored wires.

 

diyautotune.com

MegaSquirt Wiring Bundle – 23″ Long





MegaSquirt 3X Wiring Bundle – 23″