Quote:
Originally posted by Joon525
It depends on the supercharger. A centrifugal superchager can have one but doesn't HAVE to. A roots type supercharger cannot have/doesn't need one.
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You don't need a BOV with the JRSC because the compressor (turbo or SC) is positioned after the throttle body. If the throttle plate closes, the air supply to the compressor is restricted, and large amounts of air cannot be "pumped" into the engine.
When the compressor is before the throttle body (just about every turbo and Vortech car you will ever see), a blow-off or bypass valve should be used. If you're driving hard and suddenly let off the gas, the throttle plate snaps shut.. but the compressor is still spinning and trying to force air into the engine. A BOV will release this pressure and can save your compressor from getting damaged by "compressor surge".
A blow-off valve openly vents this excess pressure, making the nifty sound that people like. A bypass valve vents the pressure back into the intake before the compressor, and tends to be a lot more quiet.
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Tony S.
'03 WRX ... 12.69 @ 108.0 - full interior, stock 16s, street tires
'99 2.5RS
'97 Prelude (old car) ... 13.94 @ 100.3 - full interior, empty trunk, 17s, street tires.