Boost control on early classics

[Big Kas]

Hi all,
Maybe an amateur question but read a post a while ago about different ECU codes (z4 etc..) and how much boost each ecu runs.

My question is on the early cars how is boost actually controlled. As the waste gates are manual vacuum types and from what I know the MAP sensors only measure boost rather than control it except for the upper limit boost cut.

[asperformance]

all Subaru's from the original Legacy Turbo in 1989 have electronic boost control through the ECU....
early cars used a 3port solenoid as std and then later they switched to 2ports.....

[Big Kas]

Originally Posted by asperformance

all Subaru's from the original Legacy Turbo in 1989 have electronic boost control through the ECU....
early cars used a 3port solenoid as std and then later they switched to 2ports.....

Ah many thanks for the answer. I always thought the solenoid was just a way to measure the boost.

[asperformance]

that would be the MAP sensors job........

to run higher boost on an early car correctly you need a later MAP sensor and larger injectors / fuel pump as a min. normally

[Scott.T]

16.11psi is about the most you can run and maintain a level of safety with the MAP sensor triggered boost/fuel cut limit.
Any higher and MAP sensor tolerances seem to effect reliability of boost control and sporadic boost/fuel cut.