a mate of mine thinks his turbo needs replacing on his astra coupe and says that he needs to replace the 'actuator'. what is the actuator and what does it do?

Some turbos have a built in wastegate. The actuator controls the wastegate IE they're used to mean the same thing.

The actuator is controlled by the ECU isnt it, to limit boost rather than a mechanical wastegate system?

Common problem with the VAG 1.8T engine was the actuator sticking open causing no boost.

from what i understand the actuator controls the watsegate to allow exhaust gases to bypass the turbo to prevent over spinning of the turbo?

Yes thats what i meant

It just allows the ECU to control it rather than having the wastegate set to open on certain pressure

All it does is control the boost pressure, the actuator is just a spring really. the spring is rated at a certain pressure and when the turbo reaches that pressure the waste gate opens and lets out and excess pressure.

quote:

---

Originally posted by CraigJ
All it does is control the boost pressure, the actuator is just a spring really. the spring is rated at a certain pressure and when the turbo reaches that pressure the waste gate opens and lets out and excess pressure.

---