'99+ Miata sans OEM ECU

[AbeFM]

I had two weird issues, one: running the coils on the miata off the LED's, I cooked one to death - it was VERY hot and then I lost those cylenders, open in the trigger. I think I should have been "normal" not "inverted" on the spark output. Sigh...

The issue I have a question on:



Ok, it looks like things are working. Right now the OEM ecu is really only getting the Intake Temp sensor, but then... I don't think it's running the alternator, the battery keeps getting deader. Other than that, I was shocked how well my friend got the car idling in just a few minutes. I unhooked the IAC and it was great.

The bug: When I was using the Output Test Mode (rather, I was maning the oscilliscope while my buddy 'drove') - and when testing the coils, we couldnt' get the dwell time to below 5 ms.
Then after messing with the settings, the fuel injectors were running proportional to the spark settings, but we were asking for coils not injectors!! Even trying injectors then going back to coils had no effect - the coils stopped working and the injectors took their place. Rebooting both the MS and MT had no effect.

MegaTune 2.25p1/ 20071122

[AbeFM]

A bit of a blast from the past: Setting up the Mopar regulator on my '00 - does anyone know how to wire it in? The ECU has two wires from the altenator, which do I hook to what, and does the case need to be grounded?

Thanks!

[UnaClocker]

Yes, you have to bolt the regulator to ground. One pin, the blue wire, goes to ignition switched power. One of the wires from the alternator does as well. The other pin, the green wire goes to the other alternator wire.
Simple as that.

[AbeFM]

Thanks! I'll figure it out knowing that. One of the lines from the OEM ECU must be hot/ground, the other controlled.

[AbeFM]

Ok, picked one up - had a little trouble with it for a bit, eventually proved to myselve stuff was working by putting at 20 turn pot between power and the signal in line to the altenator, and finding out that ~0.980 volts got it charging to around 14.3V.

Anyway, armed with said knowledge, I found out the correct wiring for this. Thought I'd note it here for posperity:
To wire up NAPA part number:
New Voltage Reg Napa online MPEVR38SB $15.29 "VR38SB"
Connector for VR above Napa online ECHVRC38 $12.64 (8.99?) "VRC38"
on a '00 miata:

Ground the case, I found it convenient to mount it near the radiator overflow bottle.
Hook the BLUE wire to switched(?) "+12v" battery voltage
Hook the GREEN wire to the Grey/Red wire on the alternator, pin 1-O on the factory ECU.

I let line 1-T hang, I'm not really sure what it is, it seems to be measuring the voltage of one coil of the generator, before rectification. Not sure what that's good for, maybe you could get engine RPM out of it, or total altenator capacity.

Anyway, hooked it all up and everything works well enough. It seems to only charge to like 13.5-13.7, I think this is due to the Mopar part only putting out 580 mV, where I got better charing feeding ~980 mV. Much more than that and you're rapidly feeding 15, as much as 18V into the system. <NOTE: Post edited, wire colors were wrong!>

[UnaClocker]

Mopar voltage regulators include a thermistor in their design, they charge the battery at a different voltage based on the current ambient air temperature. That may be why your charging voltage is a bit different than you might want it to be.

And you have the blue and green from the VR backwards. I'm astounded it's working for you. Blue is ignition feed. Standard for all Chryslers from the 60's or 70's on through this century. Comes off the ignition switch as blue, and stays blue just about everywhere in the engine bay too, in my Omni. And the factory wiring to my alternator, both wires to the field were green.. Yet more confirmation that blue is ignition in, and green is field ground output. The ignition feed in is the VR's voltage sense, want an extra volt of charging? Put a diode inline before the VR.. Just don't trust the MS's voltage gauge.. Mine is always off by a volt or so. But out my Fluke multimeter and I see the real voltage. Found that out the hard way when my VR wasn't getting a good power feed (had it powered off my main relay that was getting overloaded) and overcharged and cooked my battery..

[AbeFM]

Woah! You're absolutely correct! Sorry about that, I've since edited the original post, so it's right now. Thanks, and good catch! I'd hate to have people blowing up their cars.

In fact, most of the issues I was having with mine was using an incorrect, unofficial wiring diagram for the car.

Yes, when I wired it backwards, I consistantly got over 17V, so no one do that! Thanks again for the quick eye!

[Reverant]

Nice work Abe! I'm really tempted to do this mod as well!

Jim

[AbeFM]

It's coming along. Got a weird (software?) bug I'm trying to track down, but everything else works great. Just found the Tach pin (2K) so that was the last thing making the OEM ECU even a little useful. It's been out of my car for a week, and the only two things I added was the GM AIT (which I wouldn't need if I wasn't turbo) and the altenator control box.

For a "Full, ideal" install, I'd figure out how to use the "boost sensor" for the gas tank as a barometric correction, it's already mounted under the hood, just run wires to it and take the hose off it so it sees open air. Also, I'd want to figure out how to run the AC, but that would require putting it back on my car, so I'm not sure I'll do this.

Anyway, I have tons of pics, more going up soon - if you get serious about it, let me know.
-Abe.

[Wayne Presley]

Found it

[AbeFM]

Um, 4 posts back?

[Wayne Presley]

Yeah, I only read page 1.....