This is the coolest part of the new Megasquirt rev 3 circuit board. It’s a prototyping area. Just a bunch of holes that go no where so you can add components and circuits to the MS to do other things.
I added a few more components today, a pair of 2n222 transistors, some resistors, a trimpot and a diode. The transistor on top is for the radiator fan output. The Megasquirt is already monitoring coolant temp, why not control the fan like the factory computer did. And the one below it is simply to drive the tachometer in the instrument cluster. The trimpot works with the tach output to get a hot enough signal for the cluster.