A Unichip tuner can do a custom tune at any pressure. That was my understanding as I was once looking to do this....direct from APS

 

I think there are some misunderstandings about the APS kit and unichip here -- perhaps I don't understand correctly, but here is what I thought it was:

The stock wastegate springs are set at (I think) 5-6 psi. Thus, that obviously is not what controls the boost. The boost is controlled by the Unichip X driver box (the small box next to the unichip), not the unichip. If you up the boost, you also have to change tune in the Unichip. The Unichip controls only the fuel trim and timing.

 

As I understand it, the boost control is programmed via the Unichip computer, the Unichip boost control X driver unit then pulses the boost solenoid (part of the APS TT system) to control boost pressure above waste gate actuator pressure.

George

 

Thanks for all the feedback. So the Unichip does in deed controll boost.

DXB350Z: In this case all you need is a kill switch for the solenoid. It should be a normaly open type solenoid (usualy used in this kind of application for fail safe operation), so when you cut off the current it will let all the pressure pass to the wastegate and you have the lower (wastegate set) boost level.

@calimarc: No, I am not in the service. I am not even american or have lived in the USA but I take it as a compliment regarding my english, thanks!