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Re: Blow Off VALVE Posted by Ari [Email] ![]() ![]() In Reply to: Blow Off VALVE, Quinn Kurz, Thu, 3 May 2001 05:12:47 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There is no blow off valve in the strict sense in a Saab turbo. A blow off valve dumps boost pressure if it goes too high. In the Saab, there is a closed loop system to control maximum turbo boost (wastegate actuator).
There is a device called the Turbo bypass valve, better known as the Hooter valve. When you change gears, or for any other reason close the throttle quickly, the hooter valve takes the high pressure air from the intake manifold side of the turbo and dumps it into the intake side of the turbo. In the process, it can make a hooting noise. This prevents the turbo from trying to pressurize a column of air against the closed throttle plate.
The stock hooter valve works just fine. Some folks will argue for a high performance unit that some places sell. Spend that money if you think it will help, but I'm personally not convinced. Keeping the turbo spinning is more an issue of keeping the revs up while shifting quickly. You'd only notice this if you were really pushing the car, never under normal spirited driving.
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