Quote:
Originally Posted by dhardison
Very interesting! So the thought is the 'default' PWSC vacuum line connection between the bypass valve and lower 'intake tube' doesn't reduce the vacuum enough to fully close the bypass valve, even under boost conditions?
If so, it makes sense.
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No. It doesn't use vacuum to close it. It uses vaccum to open it. But now that you mention it I'll bet there is a little bit of vavcuum in the neck itself when the car is under boost, which would futher support the need for this mod. The inlet to the rotors of the blower are bigger than the throttle body opening so when it is drawing air in it's almost for sure a slight vacuum in there.
Here is the scenario. The vaccum line that goes to the bypass valve goes to the inlet/neck of the PW housing. It never sees boost in the neck, only vacuum. The bypass valve has a spring and a diaphram in it and it gets opened by vacuum at idle & cruise. Then it relys on just a spring inside of it to keep it closed under part throttle & boost.
The re-routing of the hoses to put boost to it will give it a little extra to keep it shut under boost.