"Powered" by vacuum and pressure, a blow-off valve is, IMHO, not the way to go on our vehicles. Because they use metered air, if you "throw away" any of it, like a blow-off valve does, it could lead to a momentary rich or lean condition.
The better way to go, again IMO, is to use a bypass valve. This basically connects between the the throttle body intake and the turbo intake, and also connects to a source of vacuum/boost (like the vacuum tree). When you let off on the throttle rapidly, like when shifting, the pressure surge is bypassed around the turbo outlet back into it's inlet. This keeps the reverse surge from slowing down the turbo wheel, and incidentially is better for the turbo overall.
Of course some people like the whoosh that a blow-off valve creates.
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Hope this helps, at least a little. FWIW, I'll be installing my TurboXS bypass valve when I intall my front mount intercooler.
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EDIT: I never did say where you'd intall a blow-off on an 88; it would hook up between intercooler and throttle body, and vent to the engine compartment. You'd also again connect a line to a vacuum/boost source (vacuum tree).
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Joe F.
My
87 TC & mod list with sources
[This message has been edited by JoeCool (edited 06-29-2004).]
