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if I were you I would start thinking about doing all with speeduino.
you will have enough challenges making things work the easy way, no need to overcomplicate that.
get an alternator control addictional pcb or swap in a mk1 alternator is the easiest way.
fan control is no problem at all
Angel Ivanov wrote:
Sat Nov 14, 2020 3:59 pm
I left clt and ait shared with the ecu so it can know when to start the fan. Shared cam and crank for alternator control. I am getting a false reading -70 C CLT at operating temprature and 3 C for AIT .

Have you removed the pull up resistors from Speeduino and calbrated it to use pull ups in the OEM ECU?
Angel Ivanov wrote:
Wed Nov 25, 2020 3:27 pm
… Now I am stuck deciding to buy na alternator or to buy speedyefi alt control because I can not make the alt board myself.
Don't sell yourself short. You can also make an easy alternator control from any cheap Arduino, ATTiny, etc. Or, one of the users here with programming skills could offer to add this function to Speeduino Mazda/Ford units as an internal feature using an existing output FET. I have a standalone alternator regulator control (ARC© and MiniARC©), but they will selectably control a wide variety of alternator types with different control schemes and apply variable voltage and current, and are in testing for other alternator types.

For just this application, a simple > or < than sketch for a target battery voltage will get it done for now, and has been proven on multiple MX-5 Miatas in several countries (thanks to those volunteers). Tough to beat a $3 Nano, three resistors and one FET for an alternator regulator control. The tricks are calibration and stabilization. ;)


Only the most basic of hardware outline, this is an example of how simple an alternator regulator control can be. A VBAT output to the alternator enables charging, and grounding the signal stops it. Add code to juggle that signal for alternator output and you have a rudimentary control. Add features for under/over-charging, stabilization, dash-light control, a precision voltage reference, etc, and it becomes very capable:
MX-Nano-ARC_schem_PSIG.jpg (62.13 KiB) Viewed 448 times
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