Hi,

Few days ago I finished MS fuel & spark control for my friend's 2001 NB 1.6 turbo Miata - btw, it goes very well , even with "raw", unfinished fuel/spark maps and low boost, can't wait 1 bar boost

But now I have stupid problem with alternator - it doesn't charge battery because it was previously controlled by std ECU which is now dead, and MS is in its place now

I already tried many combinations, but all went without sucess - I took two thin wires (grey-red and grey) and connected both to +12 V - alternator started charging battery but with enormuous whining, white smoke and cloud of rubber particles from desintegrating alternator belt...I suspected that maybe it was problem in alternator belt itself (which is btw slightly too long) but my friend said that he hadn't such problems when std ECU was alive & kicking ...although belt is too long , it seems that tension is OK - it isn't too tight or too loose - it seems just right...and without two thin wires connected - it doesn't whine at all...but of course it doesn't charge anything neither

So what to do?

Anyone had such problems with his Megasquirt install?

Is there alternative alternator bolt-on replacement, that doesn't need ECU control?

Obviously putting OEM ECU and connecting it just as "alternator piggy back computer " is out of question due it's sudden and tragic death - any other idea no matter how strange or funny sounds will be welcommed ,hmmm I am out of ideas for this week...

 

The NB alternator is heavily controlled by the stock ECU, that's why we do parallel installs on top of A/C control and things like that.

I'm pretty sure you can use an alternator from an NA 1.8 and there is a different switch that activates it. Someone else will have to confirm that though.

 

it can be controlled externally. Jason C made me a little circuit (he loves circuits) that measures system voltage and outputs a PWM signal to the alternator as feedback to keep it around 13-14 volts. Post on .net and ask him about it.

 

Use an NA alternator.

 

Do the NA alternators have an internal circuit that measures system voltage in order to activate or is there an external system that goes with it?

 

NA is internally regulated

 

Good to know. Thanks man.

 

2 y8s:

Tnx, that's what I wanted to hear!

So is "JasonC SBB" from this forum man I'm looking for?

If it is , unfortunately he hasn't any e-mail adress in his public profile ... and I'm not sure how to contact him ... do you maybe have his e-mail or some other contact info?

 

Just a tip, here is what the PWM should look like at idle:



Scales are at 0.5V/div and 2.5ms/div.

Jim

 

2 Reverant:

Very interesting, so alternator field current is PWM controlled by ECU, from your waveform picture it looks like cca. 1.6 V @ 40% duty cyle on idle, and I conected it directly to 12V DC - oouchh!!!

...but the question is - is there a way to made relatively simple circuit to simulate oem ECU control in all conditions, not only at idle ?

Or even better - if two thin wires are directly connected to coils inside alternator , maybe I can use external voltage regulator from some other alternator ?

 

easeist thing would be a internally regulated alternator from a earlier car. Get some more posts up and then PM jason your question.

 

Wow, wait. So I don't have to worry about the ECU controlling the alt. on my 90 because its self regulated? And since AC/PS is out...I COULD just run MS?

 

Jason C SBB on miataforum.com will have the info you need... he's not active here.

 

Why do you insist on doing things the hardest way?

 

2 Ben:

Unfortunately , the hardest way is to mount old-type alternator from NA Mazda - I know that from your point of view you is hard to believe (large quantity of Miata spare parts in U.S.) , but in Croatia there are very few NB Miata's, let alone NA models ... so to find such alternator is very, very hard - almost impossible.


So, electronic device will be the most elegant solution momentarily - afterall alternator is already mounted and working , I just need convinient way of regulating field current.