Miata ignition inputs

[c2ron]

We're installing a microsquirt module in a stock PCM case off a 1990 miata.

There is abundant info out there on connecting the CMP and CKP ignition inputs to a full size MS board (DB 37 pins 24 and 25), but nothing about what the analogous connections to a microsquirt module are.

Could someone enlighten me?

[Matt Cramer]

Bring the crank sensor in through the opto in circuit and the cam sensor in to VR2.

[G. Jay]

Hi Matt,

Is this still your advice? I'm also working on installing a micro module into a stock 1991 Miata ECU case. Regarding the CAS inputs I see differing instructions in different documents. Notably the Microsquirt Hardware 3.3 manual says to use only the VR1 neg and VR2 neg with the signal from the crank and cam sensors shunted to Vref with a 1k resistor. I believe the negative VR input legs would alternate between 5 and 13.8 volts and the positive legs would float and lag behind the negative leg from what I can tell (I'm no EE though). I suppose it would look something like a VR output, only more stable in voltage.

Wouldn't this put noise on the Vref line? This is different than your advice above. Why not use the opto-isolated circuit?

My conclusion is that there are many possible ways to configure the details but one is best. If opto is best do I use a pull up resistor or just let the 12v work it directly?

[Matt Cramer]

The MicroSquirt MS2/Extra Hardware manual is ONLY for the plastic cased MicroSquirt.

My recommendations still stand if using the MicroSquirt Module.