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Discussion Starter #1 (Edited)
Here are some pictures. I apologize that I have yet to link to a web page with more reasonable file size/resolution.

The compressor bypass valve (CBV) is attached to the turbo housing (compressor side). There is one vacuum line (about 3/8") coming out. That connects to a metal tube on the left side (facing the front of the car) then another flexible tube which attaches to a controlling solenoid valve.

Picture of the solenoid valve.
 

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Discussion Starter #3
To the right is the positive pressure line from the intake ductwork. This is the line you want for connecting a boost gauge.
 

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Discussion Starter #4 (Edited)
Here's the vacuum line (negative pressure) that connects to the manifold. Not what my thumb is touching. It's the short curved black hose under the electrical connection.
 

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Discussion Starter #5
How it works:

The CBV is closed while the compressor is building boost. During that period the ECM directs the solenoid to route positive pressure from the intake stream to the CBV. The turbo basically uses its own pressure to help keep the valve closed, and continue building boost.

When you release the throttle, the boost pressure needs to be vented so it doesn't slam into the closed throttle plate causing a shock wave (and possible damage). When you get off the accelerator pedal the throttle plate closes and the ECM directs the solenoid to route manifold vacuum (negative pressure) to the CBV. This pulls the valve open. The boost pressure that was building in the compressor gets vented back to the pre-compressor intake lines. The opened CBV basically equalizes the pre-compressor and post-compressor pressures.

This concept of using line pressure to help open and close valves is quite common in plumbing control schemes. Your dishwasher and washing machine do the same thing with water pressure. There is probably still a spring inside the CBV, but it doesn't have to be strong enough to hold the valve completely closed in high boost conditions. The boost pressure itself does most of the work.
 

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Discussion Starter #7
SaabKing said:
  1. Can you show me a picture?
Used to have a picture in an old thread, but it's not easy to see anyway.

CBV is located on the compressor side of the turbo (that's left as you face the engine). It can be seen as a small silver can bolted to the lower part of the compressor. There is a single black vacuum line coming out of the center (about 3/8" diameter). This line snakes around the side of the engine and connects to the solenoid I'm pointing to in the above thread.

The CBV is hard to see as the view is blocked by the large intake tube and the boost control solenoid/wastegate actuator.
 

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Here are some pictures. I apologize that I have yet to link to a web page with more reasonable file size/resolution.

The compressor bypass valve (CBV) is attached to the turbo housing (compressor side). There is one vacuum line (about 3/8") coming out. That connects to a metal tube on the left side (facing the front of the car) then another flexible tube which attaches to a controlling solenoid valve.

Picture of the solenoid valve.
anyone know the name of this solenoid valve?
also is there a way to test this solenoid valve to see if it is working?
 

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In the first picture, ctrlz's finger is on the Boost Control Solenoid, the bypass valve or compressor bypass valve is directly off the turbo, and can be seen by removing the intake pipe which ouses the MAF and goes from the filter to the compressor side of the turbocharger.
 

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That may be it. Here's my shot with the valve in the center:
THis is the post in which the compressor bypass valve is pictured in the center
 

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Ok so it's called a boost control solenoid, thank you. I wanna test that first before I test the CBV. Also where can I find this part online to purchase?
 

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thesaabsite.com
 

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Oh yea I went to that site and was unsure of which one I needed.

KT4197255 - 93 2003-2010 4 Cyl Control Valve KIT Boost 12791173 superceeds to 12789106, 12789107, 12789108, 55354158 OES

12787706 - 93 2003-2010 Boost Control Valve in small hoses to Turbo OES

those are the two and both kinda say the same thing in my eyes :p are they?
 

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Actually I have to edit my responses a little bit, I can't figure out which one is which...ha I thought I knew but without looking in my engine bay I can't differentiate between what's on top of the wastegate and what's next to the throttle body. Best of luck!

EDIT: There was a previous post that stated the 12787706 is the boost control solenoid which is located on top of the wastegate. Still not sure if the other kit one is the one near the throttle body though. The general shape/geometry of the two parts is almost identical from the pictures.
 

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To the right is the positive pressure line from the intake ductwork. This is the line you want for connecting a boost gauge.
Is this the proper place to put the t for the boost gauge? I have mine above the solenoid and in between it and the intake manifold. Just curious, I've been trying to figure out why I have such a drastic change in vac pressure lately.


Sent from AutoGuide.com App
 

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How long take to change the by pass valve.?

Any help. The dealer is asking me 3,5 hours to change the bypass valve?
It is a 2.0 t q150. And valve is 55354158. how long does it take?
Thanks
 
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