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lucittm lucittm is offline
Manassas, VA
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Join Date: Apr 2007
Posts: 1,211
Are you talking about the vent line on the top of the WUR or the vacuum line on the side? For cars without a vent line, I believe there is a vent hole in the WUR beneath the spring. The purpose of the vent line is to prevent the sort of condensation that you experienced and to assist the altitude compensation on the newer 964 3.3 and 3.6 WUR. It is routed into the air filter assembly to vent the WUR. The brass vacuum line that you have on the side of your old WUR is more of a pressure line than a vacuum line. According to the 964 Bentley book (p. 157) this line will reduce the control pressure to 3.2 bar (46 psi) for the 3.3 or 2.9 bar (42 psi) for the 3.6 when it detects 250 mbar (3.6 psi) of boost pressure. Normal control pressure is specified at 4.5 bar (65.3 psi). So the purpose is to enrichen the mixture when boost comes on.

1991 964 Polar Silver Metallic Turbo Coupe
Old 08-13-2011, 08:51 AM
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