Boost control systems on a Turbo Subaru:

2 Port Solenoid System:

Boost related issues on Turbo Subarus: This is the layout of the stock turbo subaru boost control system.
Boost related issues on a Turbo Subaru: This is the layout of the stock turbo Subaru boost control system.

Starting at the turbo there should be a short pipe from a tapping in the turbo outlet duct to a plastic ‘t’ piece, this short piece of pipe should have a brass/alloy restrictor pill within it, this restrictor pill is vital to the correct operation of the 2 port solenoid system. From the ‘t’ piece you should then have another short pipe to the ‘Wastegate Actuator’, the other long pipe from the center of the ‘t’ piece should go to the wing and connect to the side port on the 2 port actuator.

It is important that it is connected to the side port as if the solenoid fails it fails safe and prevents any bleed as the pressure from the turbo will hold the solenoid closed preventing any bleed and as a result the wastegate will open at its spring rate pressure normally 0.5 BAR(7ish PSI). The final pipe in the system should connect the bottom port of the 2 port solenoid to the intake pipe post Mass Air Flow Sensor.

3 Port Solenoid System:

From the turbo outlet there should be a long pipe that goes straight to the top port of the solenoid, then another pipe connects the side port of the solenoid to the wastegate actuator, the final pipe connects the bottom port of the solenoid to the intake/resonator box, this section of pipe should have a brass/alloy restrictor pill within it.