[drwillb]

Makke, the wastegate is controlled by vacuum but the DME drives the boost solenoid which controls the amount of vacuum getting to the WG. This is not a typical on-off type of solenoid control. There is a PWM signal that cycles the solenoid very quickly in order to get variable vacuum output to the solenoid, like a fuel injector.

The vacuum is used to push the WG closed, in varying amounts, from its normally full open position. If the vacuum pump fails, a vacuum line leaks, the boost solenoid fails, or the WG diaphragm fails then the WG will not operate and will default to open condition. This is opposite to how most boost control systems have worked before but it’s pretty smart because WG system failure lets the engine continue to operate as a NA engine and you’ll get the reduced power notice on the dash. To answer your question more directly: the spring tension on our WG diaphragm is used to keep the WG open and the vacuum works against the spring to close the WG.

Just drive it like you stole it and you’ll always have boost.

BTW you will soon want a tune after you get hooked on boost. Why run at 9 psi when 15 is just a tune away?