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An FI "farkle" that I'm planning to add to the EX250 is an Arduino Nano controlled Manifold Absolute Pressure sensor array (2 MAP sensors for the EX250).
This unit will read simultaneously from a dedicated MAP sensor on each of the two cylinders and it will discriminate for the lower signal (i.e. more vacuum) and then forward only the lower signal (on a microsecond-by-microsecond basis) onward to the MicroSquirt's MAP sensor input line (pin 24 if I remember correctly). Between the Arduino Nano and the MicroSquirt will be a digital to analog converter (DAC) to change the digital Nano output into something the MicroSquirt can use.
This will make the EX250's MAP signal information much more useful to the MicroSquirt. But even with that improvement I'm expecting to run the engine in ITB mode (which is Speed Density when below a certain yet-to-be-decided MAP kPa value, and switching to Alpha N above that value).
Also, the Nano will be monitoring the Cylinder #1 MAP vacuum signal for each time it goes below a pre-specified minimum value. This information will be used to generate the equivalent of a Hall-type Camshaft speed sensor. This will allow the MicroSquirt to run the engine in full sequential mode.
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