I’m looking for advice on connecting a boost control solenoid to my MS3X using the “boost” wire (PP3). I see 3 possible ways to wire this, and I’m not sure which is correct:

a) 12V to one BCS wire, MS3X boost wire to the other BCS wire.
b) Same as a), but with a diode between the two wires to control kickback (just like the BAC wiring).
c) Use a MOSFET transistor with a couple of resistors and a diode (pre-MS3 guys were using this setup), as shown here:


DIYautotune's boost control solenoid description says: "One wire connects to a 12 volt source, the other to the Megasquirt, the valve wiring is not polarized so it does not matter which wire you run to 12v+ and which to switched ground at the EMS."

This seems to suggest option a, but I would like to get confirmation before I move forward.

Thanks.

 

option a its the correct way.

 

The MS3X outputs can drive the solenoid directly. They are also clamped internally but I still like to put a diode in the harness.