Race Core Knowledge base

Sensors & outputs Solenoid

output Solenoid

Boost solenoid

3-port MAC / Bosch BCS · output · Solenoid

3-port, 2-wire solenoid. Electrical side is a high-side or a spare low-side. Pneumatic side is wastegate control, not a vacuum tree decoration.

Boost solenoid

Typical parts: Mack-style 3-port; MAC 36A-AAA-JDAA-1BA 3-port; Bosch 3-port BCS; GM boost solenoid

Note — XOR with VVT 4. Highside 4 is also VVT 4 in the default assignment. Four-cam VVT plus boost needs a spare low-side for the solenoid.

Device pinout

Looking into the solenoid. Two electrical cavities. Ports are moulded 1 / 2 / 3 on the body.

Boost solenoid connector pinout

  • Connector: 2-way on the solenoid
  • Layout (looking into the part): 1 · 2; polarising key top
Device pinFunctionTypeRace CoreTunerStudio
112 V (high-side or main-relay rail)High-sideA14Highside 4
2Return (head, or ECU low-side if 12 V is from the rail)GroundHead / spare low-side—

Wiring notes

  • Default electrical: Highside 4 sources 12 V, pin 2 to power ground. Alternative: pin 1 from main-relay 12 V, pin 2 on a spare low-side.
  • Typical 3-port (MAC 36A family): COM to the wastegate actuator, NO to manifold pressure, NC to vent. Off = gate vented (spring closes the gate). On = pressure to the gate (opens it, drops boost). Confirm on the valve you have — port stamps differ.
  • Short, equal-length hose. A 2 m run of 4 mm hose is a boost controller with lag.
  • Enable boost control only after idle is stable. A first-start with 100 % duty and a 1.5 bar spring is how housings leave the car.
  • A Mack-style 3-port is the same electrical part as a MAC 3-port: two wires, three hoses. The shop drive is PWM. Default in this library is Highside 4 sourcing 12 V. A ground-switched valve wants switched 12 V on one pin and a spare low-side on the other. That spare low-side cavity is TBD — do not borrow an injector pin.
  • Read the port stamps on the valve. COM, NO, and NC are not in the same places on every 3-port body.

Failure modes

  • Boost pegs at the spring: the solenoid never opens, or COM and the vent port are swapped so “on” still vents.
  • Boost falls as duty rises when you expected the opposite: NO and NC are reversed for the plumbing you chose. Fix the hoses, or invert the output in software — not both.
  • The solenoid ticks and VVT 4 moves with it: Highside 4 is shared. A four-cam engine needs a spare low-side for boost, and that cavity is TBD until you assign one.

See also