How is the boost pressure controlled. Stupid question I know. Not owning
a scoob for very long I would like to know. I have MY02 Uk.
Does the ecu control boost and boost spikes, actuator (yes I know this
does play a part). On old turbo cars there were many variations on how
it was controlled. Some very primative other a bit more precise.
Anyone ?

Cheers

 

I'll try and keep it simple.

There is a pipe from the pressurised side of the turbo that goes to the wastegate actuator. The higher the pressure, the more the wastegate opens.

There is also a pipe that 'T's off this pipe. This T goes to a valve (wastegate solenoid) that is controlled by the ECU. What the valve does is bleed away pressurised air, so that the wastegate does not get the full effect of the pressurised air in the pipe.

There is one other important part and that is the boost control restrictor. That sits in the pressurised pipe and has a tiny hole in it. This delays the pressurised air's effect on the wastegate actuator. The smaller the hole, the more the delay and the more the boost will spike. But if the hole is too big, the actuator opens too quickly and the boost target is never achieved.

Hope that helps.

 

Cheers.
Good explaination, almost the same as a cossie and a Renault 21 Turbo, which
I have had both, so I know roughly now how it works
Ta