woah. That's pretty shitty. I guess you didn't check battery voltage with old alternator?

I've had issues with the MS3 voltage readings in the past, found out I hated their math, but after I fixed a dumb wiring issue (transistors used to drive dash LED's) enough of it went away I could live with it.

Like all things megasquirt - if the car runs, no one cares why it doesn't work right.

Glad this is coming together for you. Guess I should get a sender as well. :-)

The problem came back, now its reading 1V low.
Measured VRef and its 4.9V. I'm going to look into the wiring and ask on msextra.

Any thoughts on upgrading U5, though? Its 500ma in stock form and if I'm going to use VRef to drive a bunch of sensors, I probably want more current than that.

That's not a terrible thought. I guess you could unplug a couple sensors, see if it gets better. :-) You'd think most of the measurements would be as-a-function-of the 5V being fed them, but yeah, then wiring would mean different sensors are getting a different voltage, and things all around would be bad.

Not sure why the MS is seeing the wrong voltage, though - that's a sign of something else. I did figure out it can't really read the right voltage since the circuit it uses... But I think it's off by less than a volt. Anyway, it seems easy enough to pull that chip - or bypass it temporarily to see if things improve.

LM2940CT.

Do I need to replace anything else to support higher current? LIke L2, C20, C22?

You could upgrade L1 and L2 with a 4A equivalent. Not sure on a digikey code, I buy them locally.

I would highly suggest that you replace C16 and C17 with 33uF/50V aluminum electrolytic caps anyway.

C20 is irrelevant, C22 should be ok at 4.7uF, I don't think these sensors have any sort of transient requirements.

awesome, thank you so much!

To keep this thread going...

I finally got time to work on the car. I looked at the poor state of the wiring harness - it was modified so many times over the past 3 years... that I decided to redo it.

So far:
https://www.miataturbo.net/attachmen...ine=1401892248
https://www.miataturbo.net/attachmen...ine=1401892248
https://www.miataturbo.net/attachmen...ine=1401892248

My approach is as follows: I'm keeping the chassis wiring mostly intact because it works and I don't care. Eventually I'll redo the chassis wiring as well.

As for engine wiring, I'm removing all traces of the current engine wiring and adding a new sub-harness. I'm also adding a separate fusebox just for the engine stuff.

https://www.miataturbo.net/attachmen...ine=1401930886

Started on the engine harness. Coming along nicely!
Tomorrow I get the a few new connectors and a fuse box. Hopefully can finish by friday!

Last night I made a fusebox for the engine harness (and horn, lul)
https://www.miataturbo.net/attachmen...ine=1402067853

Its going tobe mounted in the glove box (or the space where a glove box used to be...)

Tits. Need a parts list right meow.

Ok, hot damn that's an awesome fuse box. I've been looking for something like this for one of my projects. Did that come from Waytek?

Got a schematic for what you're doing? How big was your order of OEM connectors from Eastern Beaver?

I'm kind of freeballing at the moment. I have 5 relays which is more than I need but hey, might as well use them all. So, boost control solenoid and idle control valve get their own relay which will be switched on by MS when car is running - so it doesn't hum when car is off - I hate that shit. I'll write up a schematic later.

As for the connectors, I ordered from Ballenger and really I just got the TPS, IAC and CAS because they were old and shitty.

I have a total of 5 OEM mazda connectors remaining in my car

- NA CAS (using only 3 wires, tho)
- NA CLT
- NB TPS
- NB Idle
- NA8 Crank sensor

Everything else is some generic connector, lol

yes, its from waytek. Bussman 15300.
Series 15310 60-Position RTMR

Wow, that box is surprisingly cheap. o_O


What plugs/termination does it take for the wiring running to/from it?

Metripack 280 Tangless, if I read correctly. Should crimp just fine in my open barrel uninsulated ratchet crimper. That box is cheap. And waterproof. I think I have another project to add on to my cars....

Um, I thought they got the idle to stop when the car wasn't running? I remember whining on the forums about it and I thought they fixed it. Maybe they told me I was an asshole and didn't do it - that's more typically the response I get over there. Anyway, perhaps updating firmware would fix it.

And, shouldn't boost also be off when pressure is negative? I wonder if you couldn't use a generic output to do that - I mean, over ride the output when RPM < 50.

With the AEM, i set the boost control line at atm pressure and below to 0% duty. no hum when the car was off/just cruising. solenoid will last a lot longer that way too LOL.

Good point.

I thought a bit more about the fusebox wiring and realized I forgot a bunch of circuits (cam/crank, O2)