Turbo wastegate actuator query?

[Wee_monkey1987]

I bought a fully reconditioned Garett T2 turbo recently however i'm a little confused with the internal wastegate attenuator. Most turbo's i know of have one hose connection that goes from the diaphragm wastegate actuator to the inlet turbo housing to prevent over boost, but mine has two, as seen below,

http://i1245.photobucket.com/albums/gg585/wee_monkey1987/Turbo.jpg

What's the second for?

[Kwik-Nick]

You can use each hose connector, one work on vacuum, another one on boost. They both do the same job, but if you use the vacuum one you have to connect it after the throttle body, if you use the boost one, have to be connected before the throttle body. Some cars use both connectors with cycle valve to control the boost.

[Ross]

quote from http://en.wikipedia.org/wiki/Wastegate:

Standard wastegates have one port for attaching the boost control line from the charge air supply line or boost control solenoid. This is the most common configuration and the only type of configuration found on internal wastegates.

A dual port wastegate adds a second port on the opposite side of the actuator. Air pressure allowed to enter this second port aids the spring to push harder in the direction of closing the wastegate. This is exactly the opposite of the first port. The ability to help the wastegate remain closed as boost pressure builds can be increased. This also adds further complexity to boost control, requiring more control ports on the solenoid or possibly a complete second boost control system with its own separate solenoid. Use of the second port is not necessary. Secondary ports, unlike primary ports, cannot be simply attached to a boost control line and require electronic or manual control to be useful. C02 can also be used to apply pressure to the second port, to control boost on a much finer level.

[Ross]

You can use each hose connector, one work on vacuum, another one on boost. They both do the same job, but if you use the vacuum one you have to connect it after the throttle body, if you use the boost one, have to be connected before the throttle body. Some cars use both connectors with cycle valve to control the boost.

See the above. Really not sure where you've got this info from about before/after the TB or them doing the same job.

[Wee_monkey1987]

Thanks ross but your link tells me it can't be found and when you look up wastegate on wikipedia that extract isn't there either way i can basically just block up/cap the secondary port (below the spring port)

[Ross]

you dont even need to block the lower one, just run it open - use the top one as per normal. :)

[axsaxoman]

or use a 4 way valve and get better control and boost where you want it