[hgtorin]

Hi all, I've tried searching around the forum to see if anyone has come across the same issue, but to no luck as yet.
I've recently purchased an NA6 PNP unit and have loaded on the default tune with the second latest firmware (202207.2), as that is what TS said the tune was designed for (202207).
I've had some minor tuning issues, I suspect due to my lack of a wideband O2 sensor which is on the priority list to get installed.

TL;DR: The main issues I have been having are as follows: my alternator is no longer charging my battery, and shortly after each time my battery has died, the Speeduino no longer works or connects to TS, the car just cranks and nothing else. After a reflash of the arduino it seems to all work again - until it just doesn't.

A more detailed description of whats happened:
After a week of having the Speeduino installed, my car wouldn't start, it just was cranking over and seemingly nothing else. I tried to connect to TS but it was not able to see any ECU connected, but my COM4 port was able to see an Arduino 2560 Mega as expected.
I reflashed the 202207.2 firware onto the arduino, and it connected to TS after that. After a few tries at adjusting spark advance my battery clunked out so I had to charge it up and I jsut reset all the spark values back to default. After removing the battery, charging it, and plugging it back in, the car worked fine for ~6 days. That brings us to mid last week where it just stopped working in the middle of the road, and the battery was so flat that my hazards stopped working... so for some reason the alternator is no longer charging the battery - still trying to figure that one out.
I was able to park the car and bring the battery home to charge it, and drive back in another car to the MX5 to put a full battery in, and that got me back home.
The next day, I get in to drive it, the plan was to just trickle charge the battery each night until figuring out the alternator issue; but, it just refused to start all together, same as I had before - cranking but nothing else. However, this time it seems to connect up to TS. Battery voltage after charge was 13.4V.

Is there any advice on what I can do or check to see what has gone wrong? I was hoping to fire up the engine to see what voltage the battery is at when the alternator is 'supposed' to be engaged to see if it is charging the battery or not, but I cannot even get it that far...

[JHolland]

The MX5 requires additional circuitry to control the alternator, if you bought a PNP ECU than it should be included, you should ask the vendor because it is not a part of the Speeduino project.
Some PNPs have customized firmware so again you need to check with the vendor, the standard Speeduino download may not work properly.

[hgtorin]

The MX5 requires additional circuitry to control the alternator, if you bought a PNP ECU than it should be included, you should ask the vendor because it is not a part of the Speeduino project.
Some PNPs have customized firmware so again you need to check with the vendor, the standard Speeduino download may not work properly.

(The ECU was purchased second hand, so this forum seems to be the best place I can go to get info on how to get it working. )

So does this mean that the Speeduino PNP ECU shouldn't be controlling anything to do with the alternator? Or should the circuitry built into the arduino's breakout board deal with it on a hardware level?

I've found this wiring diagram: https://www.miataforumz.com/1990-200-Mi ... 90diag.pdf , which seems to indicate that the alternator should be engaged on ignition, and in theory should not be effected by a change in ECU...

As for the current firmware, the version I am using is from Speedyloader, as is the NA6 base tune as recommended on the wiki page: https://wiki.speeduino.com/fr/boards/MX5_PNP

[JHolland]

The alternator control circuitry would normally be built into the PNP.

[jonbill]

Which PNP board is it? This one?
https://wiki.speeduino.com/en/boards/MX5_PNP

[jonbill]

Might help:
viewtopic.php?t=2427

[PSIG]

Not to derail the direction, but only to state the simplicity of basic regulation control. Speeduino can regulate the alternator to a target voltage with just an AUX IO output, or other output reconfigured. No need to complicate with a standalone circuit.

I made an Arduino sketch to control these things with one transistor and one resistor, and field testing here and overseas went well, but dropped the idea (for MX-5s) when it was realized simple control could be sourced right in the ECM outputs. The MiniARC multi-make design is still viable for other makes that require other regulating signals, such as PWM, or more advanced charging schemes; but basic function for ECM-controlled MXs is pretty easy.

[JHolland]

I may have complicated this already. Looking at this thread on a PC I can see that you profile image is of a MK1 MX5 and you did put NA6 in the title. Your alternator probably isn't controlled by the ECU, my apologies.

[hgtorin]

Not to derail the direction, but only to state the simplicity of basic regulation control. Speeduino can regulate the alternator to a target voltage with just an AUX IO output, or other output reconfigured. No need to complicate with a standalone circuit.

I made an Arduino sketch to control these things with one transistor and one resistor, and field testing here and overseas went well, but dropped the idea (for MX-5s) when it was realized simple control could be sourced right in the ECM outputs. The MiniARC multi-make design is still viable for other makes that require other regulating signals, such as PWM, or more advanced charging schemes; but basic function for ECM-controlled MXs is pretty easy.

So, to someone who is more than happy to tinker around with Arduino's but doesn't know an awful lot about them, is it possible to configure one of the pins to regulate the alternator through the NA6 PNP breakout board through TS? There is a programmable output setting within TS which I believe may be the way to go, I'm just unsure how the program assigns its output pins.

Also, on the comment above this one, JHolland says that the NA6 MX5 shouldn't have its alternator controlled by the ECU anyways so perhaps I'm looking at the wrong thing and the alternator has just coincidentally died at the same time as swapping the ECU?

[hgtorin]

Might help:
viewtopic.php?t=2427

I have checked out that topic and as far as I am aware, since my MX5 is a 1989 model, its as early as it gets in terms of wiring, so in theory the alternator shouldn't be controlled by the ECU.
And yes the ECU I have is the MX5 NA6 PNP unit that you linked. There doesn't seem to be anything outlined in that Wiki page which I followed for install about additional control or wiring needed for the alternator, so if for whatever reason the alternator is expecting some sort of signal from the ECU it could be a firmware issue?
From what I've found on other forums the alternator should just self govern.