Has anyone here had luck using a mechanical ball and spring type boost controller with the stock turbo long-term?
Tom Bryant pointed out that the wastegate actuator on these turbos is unique in that it's mounted directly to the exhaust housing and uses a constant stream of flowing boost (through 2 ports with a restricted exit orifice) to cool the diaphragm and keep it from burning up. Since these ball and spring controllers provide no air to the wastegate actuator until peak boost is reached, under partial boost conditions the wastegate would operate uncooled and experience a potentially shortened lifespan.
I have a G-valve type controller like this one:
I am considering adding a small adjustable screw valve, to allow an adjustable orifice "bypass flow" for cooling the wastegate without opening it. I would just set the G-valve to a specific opening pressure (say 15psi) and then slowly adjust the bypass valve closed until it's as open as possible while still allowing the boost set-point to be reached.
Bypass valve example:
Any comments/suggestions? I want to stick with the stock turbo because I'm not hoping to get super aggressive with performance modifications. I'm only hoping to add about 20 reliable horsepower, so I don't need to downshift as often climbing grades.