Quote:
Originally Posted by A_VAS
bypass is a vacuum signal operated canister, with a restricter in the vacuum line to slow it's operation. It vents off the pressurized air from the rotors under light load, cruise, idle.
As vacuum drops to near 0, depends on engine load and throttle position, it will slowly close. The boost pressure doesn't affect this canister, it only operated off vacuum. When vacuum drops, the canister diaphram closes the bypass valve and pressurized air then hits the intake ports.
That's my explanation of it's operation....at what vac reading does it start to work, you'd probably have to put a vac gage on it and drive to see for sure. At 0 vac (wot) it for sure is reacting, but not immediately since the restrictor in there slows it down. Takes 1 sec or so to fully open the diaphram if you watch in on a dyno for instance
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Very good explanation. The bypass valve itself it actually spring loaded and at the point that the inlet reaches 3 in/Hg of vacuum the diaphragm in the actuator no longer has sufficient vacuum behind it to hold open the bypass valve against the spring's tension. This is when it starts to close and will be fully closed by the time you reach 0 vacuum/boost.